Wagner, J., Rösener, B., Schulz, N., Rattunde, M., Moser, R., Manz, C., ...
Shokhovets, S., Köhler, K., Ambacher, O., Gobsch, G.
We present the imaginary part of the dielectric function of n-type wurtzite GaN measured by spectroscopic ellipsometry in the spectral range of 3.2-4.5 eV at room temperature for electron...
Reduced nonthermal rollover of wide-well GaInN light-emitting diodes (2009)
Maier, M., Köhler, K., Kunzer, M., Pletschen, W., Wagner, J.
Nonthermal rollover (or efficiency droop) of the electroluminescence (EL) efficiency has been investigated for near-UV-emitting (AlGaIn)N single-well light-emitting diodes (LED) with varying GaInN...
H- and D-related mid-infrared absorption bands in Ga(1-y)In(y)As(1-x)N(x) epitaxial layers (2009)
Alt, H.C., Messerer, P., Köhler, K., Riechert, H.
Epitaxially grown ternary and quaternary layers of GaAs based dilute nitrides have been exposed to H+ and D+ ion bombardment to investigate the interaction between hydrogen (deuterium) and nitrogen....
Manz, C., Yang, Q.K., Rattunde, M., Schulz, N., Rösener, B., Kirste, L., ...
Molecular beam epitaxial growth and operation of quaternary GaInAsSb/AlGaAsSb-based optically pumped vertical-external-cavity surface-emitting lasers (VECSEL) emitting at wavelengths 2.X mu m are...
Polyelectrolyte complexes as a "smart'' depot for self-healing anticorrosion coatings (2009)
Grigoriev, D. O., Köhler, K., Skorb, E., Shchukin, D. G., Möhwald, H.
Determination of surface potential of GaN:Si (2009)
Köhler, K., Maier, M., Kirste, L., Wiegert, J., Menner, H.
The surface potential of GaN:Si is determined for Si doping from 2.4 x 10(exp 17) cm-3 to 2.3 x 10(exp 19) cm-3 in layers grown by low pressure metal-organic vapor-phase epitaxy. We used the sheet...
Recent developments in high-power, short-wave mid-infrared semiconductor disk lasers (2009)
Burns, D., Kemp, A.J., Rösener, B., Schulz, N., Manz, C., ...
Many applications exist for high performance lasers in the short-wave, mid-infrared spectral regime between 1.9 and 2.5µm - from long-range communications systems through to remote atmospheric gas...
Time-resolved characterization of external-cavity quantum-cascade lasers (2009)
Hinkov, B., Yang, Q., Fuchs, F., Bronner, W., Köhler, K., Wagner, J.
We report on the temporal and spectral evolution of the lasing spectrum of an external-cavity quantum-cascade (QC) laser operated in pulsed mode. Time-resolved lasing spectra, recorded on nanosecond...
Waltereit, P., Müller, S., Bellmann, K., Buchheim, C., Goldhahn, R., Köhler, K., ...
We systematically investigate Al(0.22)Ga(0.78)N/GaN high electron mobility transistors with GaN cap layer thicknesses of 0, 1, and 3 nm. All samples have electron mobilities around 1700 cm2/Vs and...
Quantum cascade detectors (2009)
Giorgetta, F.R., Baumann, E., Graf, M., Yang, Q.K., Manz, C., Köhler, K., ...
This paper gives an overview on the design, fabrication, and characterization of quantum cascade detectors. They are tailorable infrared photodetectors based on intersubband transitions in...
Maier, M., Passow, T., Kunzer, M., Schirmacher, W., Pletschen, W., Kirste, L., ...
Near-UV LEDs emitting at around 400 nm can be used e.g. as pump light source in tri-phosphor RGB white luminescence-conversion LEDs with high color rendering. Although non-thermal roll-over decreases...
Terahertz imaging with bow-tie InGaAs-based diode with broken symmetry (2009)
Kasalynas, I., Seliuta, D., Simniskis, R., Tamosiunas, V., Köhler, K., Valusis, G.
A silicon-lens coupled bow-tie InGaAs-based diode with broken symmetry is demonstrated for terahertz imaging applications below 1 THz at room temperature. Transient features and the dynamic range of...
Manz, C., Köhler, K., Kirste, L., Yang, Q.K., Rösener, B., Moser, R., ...
Molecular beam epitaxial (MBE) growth and lasing operation of quaternary GaInAsSb/AlGaAsSb-based optically-pumped vertical-external-cavity surface-emitting lasers (VECSEL) emitting at a wavelength of...
Homogenizing and mixing of dairy products at reduced energy input. (2009)
Hensel, A., Kraut, M., Köhler, K., Aguilar, F., Schubert, K., Schuchmann, H.P.
2nd Internat.Congress on Green Process Engineering, Venezia, I, June 14-17, 2009
Melt emulsification - is there a chance to produce particles without additives? (2009)
Köhler, K., Hensel, A., Kraut, M., Schuchmann, H.P.
8th World Congress of Chemical Engineering (WCCE8), Montreal, CDN, August 23-27, 2009
Oil-in-water and water-in-oil emulsions. (2009)
Schuchmann, H.P., Köhler, K., Aguilar, F., Hensel, A.
Hessel, V. [Hrsg.]
Maier, M., Passow, T., Kunzer, M., Pletschen, W., Liu, S., Wiegert, J., ...
Three series of 400 nm light-emitting diodes (LED) with GaInN well widths ranging from 3 nm to 18 nm were grown on freestanding GaN- substrates, on ultra low dislocation GaN templates on sapphire,...
Power scaling of GaSb-based semiconductor disk lasers for the 2.X µm wavelength range (2009)
Rattunde, M., Rösener, B., Hempler, N., Burns, D., Moser, R., ...
In this paper, we will present our results on different high-power GaSb- based optically pumped semiconductor disk lasers (OPSDLs) emitting in the 1.9-2.8 µm wavelength range, with the emphasis on...
Optical stand-off detection of explosives and improvised explosive devices - OFDEX (2009)
Schnürer, F., Schweikert, W., Heil, M., Bunte, G., Krause, H., Fuchs, F., ...
The Fraunhofer Society pooled its know-how in the fields of explosives, laser spectroscopy, semiconductor-laser design and system integration in order to develop optical technologies for the...
Large-area terahertz emitters based on GaInAsN (2009)
Peter, F., Winnerl, S., Schneider, H., Helm, M., Köhler, K.
We present large-area emitters based on GaInAsN which show efficient THz emission for excitation wavelengths up to 1.35 µm. The substrate material consists of a 1000 nm Ga1-yInyAs1-xNx (y = 0.11 and...
Broad band tunable quantum cascade lasers for stand-off detection of explosives (2009)
Hinkov, B., Fuchs, F., Kaster, J.M., Yang, Q.K., Bronner, W., Aidam, R., ...
We present experimental results on a Quantum cascade laser (QC laser) embedded in an external cavity. These results were obtained with a broadly tunable laser exceeding 80 cm-1 covering a...
GaSb-based optically pumped semiconductor disk laser using multiple gain elements (2009)
Rösener, B., Rattunde, M., Moser, R., Manz, C., Köhler, K., Wagner, J.
We report on the realization of an optically pumped semiconductor disk laser (SDL) emitting at 2.25- m wavelength with a cavity containing two separately pumped (AlGaIn)(AsSb) gain chips. Compared to...
Growth and electrical properties of AlxGa1-xN/GaN heterostructures with different Al-content (2009)
Köhler, K., Müller, S., Waltereit, P., Kirste, L., Menner, H., Bronner, W., ...
High electron mobility transistor material and device properties based on AlxGa1-xN/GaN heterostructures with an Al-content ranging from 12 to 35% are presented. The Al-content of the low pressure...
InGaAs/AlAsSb quantum cascade detectors operating in the near infrared (2008)
Giorgetta, Fabrizio R., Baumann, Esther, Hofstetter, Daniel, Manz, C., Yang, Q., Köhler, K., ...
InGaAs/AlAsSb quantum cascade detectors operating in the near infrared (2008)
Giorgetta, Fabrizio R., Baumann, Esther, Hofstetter, Daniel, Manz, C., Yang, Q., Köhler, K., ...
Design of a Microstructured System for Homogenization of Dairy Products with High Fat Content (2008)
Köhler, K., Aguilar, F., Hensel, A., Schubert, K., Schubert, H., Schuchmann, H.P.
High pressure homogenization of dairy products is today state of the art but limited by the fat content (max 17 vol.-%). This article describes the development of a novel simultaneous homogenization...
High-power, (AlGaIn)(AsSb) semiconductor disk laser at 2.0 µm (2008)
Hempler, N., Rösener, B., Schulz, N., Rattunde, M., Manz, C., ...
We report a high-power (AlGaIn)(AsSb) semiconductor disk laser emitting around 2 ?m. With a diamond heat spreader used for thermal management, a maximum output power of just over 5 W and slope...
Dreyhaupt, A., Peter, F., Winnerl, S., Nitsche, S., Wagner, M., Schneider, H., ...
Scalable antenna structures based on photoconducting GaAs substrates are excellent devices for both generation and detection of pulsed terahertz radiation. Scalable emitters yield more intense...
The surface potential of GaN:Si (2008)
Köhler, K., Wiegert, J., Menner, H.P., Maier, M., Kirste, L.
The surface potential of GaN:Si, of fundamental interest for knowledge of the electrostatic potential and electric field strength, is determined for Si doping in the device relevant range from...
Band anticrossing in diluted AlxGa1-xAs1-yNy (x <= 0.37,y <= 0.04) (2008)
Procz, S., Fiederle, M., Kunzer, M., Köhler, K., Wagner, J.
We show that the conduction band structure of dilute AlxGa1-xAs1-yNy with x
Kunzer, M., Maier, M., Köhler, K., Kaufmann, U., Wagner, J.
Temperature and excitation power dependent photoluminescence spectroscopy on GaInN UV-violet LED structures allows to separate the influence of the quantum confined stark effect (QCSE) from carrier...
Winnerl, S., Peter, F., Nitsche, S., Dreyhaupt, A., Zimmermann, B., Wagner, M., ...
We report on scalable photoconductive antennas for both emission and detection of terahertz (THz) radiation. The concept yields THz emitters with high efficiencies for the conversion of near-infrared...
OFDEX-optial stand-off detection of explosives and improvised explosive devices (2008)
Bronner, W., Fuchs, F., Köhler, K., Wagner, J., Wild, C., Bunte, G., ...
Sakowicz, M., Lusakowski, J., Karpierz, K., Grynberg, M., Knap, W., Köhler, K., ...
Detection of terahertz radiation by two dimensional electron plasma in high electron mobility GaAs/GaAlAs transistors was investigated at cryogenic temperatures in quantizing magnetic fields....
Rösener, B., Schulz, N., Rattunde, M., Manz, C., Köhler, K., Wagner, J.
We report on the output power performance and beam profile analysis of an optically pumped GaSb-based vertical-external-cavity surface-emitting laser operating at 2.25 mu m. The use of a SiC...
Enhancement of (AlGaIn)N near-UV LED efficiency using freestanding GaN substrate (2008)
Maier, M., Köhler, K., Kunzer, M., Wiegert, J., Liu, S., Kaufmann, U., ...
The effect of freestanding GaN-substrates with low defect density (DD) on the electroluminescence (EL) characteristics of near UV-LEDs has been investigated. Three series of LED-structures with...
Current- and temperature-induced beam steering in 7.8-µm emitting quantum-cascade lasers (2008)
Hinkov. B., Fuchs, F., Bronner, W., Köhler, K., Wagner, J.
We report large current- and temperature-induced beam-steering effects, observed in the far-field distribution of InP-based quantum-cascade lasers emitting around 7.8-µm wavelength operated in...
Terahertz emission from a large-area GaInAsN emitter (2008)
Peter, F., Winnerl, S., Schneider, H., Helm, M., Köhler, K.
A large-area interdigitated terahertz emitter based on molecular-beam epitaxy grown GaInAsN with an additional AlGaAs heterostructure is investigated as a terahertz source for excitation wavelengths...
SIMS depth profiling of Mg back-diffusion in (AlGaIn)N light-emitting diodes (2008)
Kirste, L., Köhler, K., Maier, M., Kunzer, M., Maier, M., Wagner, J.
The Mg doping profiles in close proximity to the (AlGaIn)N/GaN QW active region of group III-nitride light-emitting diodes grown by low pressure metal-organic vapor-phase epitaxy on sapphire...
Terahertz detection by the entire channel of high electron mobility transistors (2008)
Sakowicz, M., Lusakowski, J., Karpierz, K., Knap, W., Grynberg, M., Köhler, K., ...
GaAs/ALGaAs and GaN/AlGaN high electron mobility transistors were used as detectors of THz electromagnetic radiation at liquid helium temperatures. Application of high magnetic fields led to the...
GaInAs/ AlAsSb quantum cascade lasers: A new approach towards 3-to-5 µm semiconductor lasers (2008)
Yang, Q.K., Manz, C., Bronner, W., Mann, C., Köhler, K., Wagner, J.
At present GaInAs/AlInAs based quantum cascade (QC) lasers represent the state-of-the-art with respect to the short-wavelength (< 5 µm) performance of the QC laser concept. This performance,...
(AlGaIn)N UV LEDs for integrated metal-oxide based ozone sensors (2008)
Wagner, J., Wang, C.Y., Maier, M., Kunzer, M., Passow, T., ...
There is high demand for compact low-cost ozone (O3) sensors. It has been shown that indium oxide (In2O3) thin films grown by metal-organic vapor-phase epitaxy (MOVPE) act as an O3 sensitive...
Coherent acoustic phonons in nanostructures (2008)
Dekorsky, T., Taubert, R., Hudert, F., Bartels, A., Habenicht, A., Merkt, F., ...
Phonons are considered as a most important origin of scattering and dissipation for electronic coherence in nanostructures. The generation of coherent acoustic phonons with femtosecond laser pulses...
Rattunde, M., Schulz, N., Rösener, B., Manz, C., Köhler, K., Wagner, J., ...
We report on recent advances in the performance of GaSb-based optically pumped semiconductor disk lasers (OPSDLs), emitting in the 2.0 - 2.3 µm wavelength range. Both barrier pumped OPSDL (using 980...
Optically pumped (AlGaIn)(AsSb) semiconductor disk laser employing a dual-chip cavity (2008)
Rösener, B., Schulz, N., Rattunde, M., Moser, R., Manz, C., Köhler, K., ...
A GaSb-based optically pumped semiconductor disk laser with two separately pumped chips is presented. With this dual-chip configuration, an output power of 3.3 W at 2.25 µm wavelength was recorded...
Midinfrared quantum cascade detector with a spectrally broad response (2008)
Hofstetter, D., Giorgetta, F.R., Baumann, E., Yang, Q.K., Manz, C., Köhler, K.
A midinfrared quantum cascade detector with a spectrally broad (deltaE/E=27.3%) response is designed, fabricated, and tested. This detector consists of 26 differently designed active region stages in...
Schulz, N., Rösener, B., Moser, R., Rattunde, M., Manz, C., Köhler, K., ...
An improved active region concept for GaSb-based optically pumped vertical-external-cavity surface-emitting lasers (VECSELs) is presented. The concept is based on Ga(x)In(1-x)As(y)Sb(1-y) quantum...
Rösener, B., Schulz, N., Rattunde, M., Manz, C., Köhler, K., Wagner, J.
We report the realization of GaSb-based optically pumped vertical-external-cavity surface-emitting lasers (VECSELs) emitting at 2.25 µm which are capable of multiple-Watt output power. VECSEL...
Current-and temperature-induced beam steering in 7.8-mu m emitting quantum-cascade lasers (2008)
Hinkov. B., Fuchs, F., Bronner, W., Köhler, K., Wagner, J.
We report large current- and temperature-induced beam-steering effects, observed in the far-field distribution of InP-based quantum-cascade lasers emitting around 7.8-mu m wavelength operated in...
Hudert, F., Bartels, A., Dekorsky, T., Köhler, K.
The doping profile in different n-doped GaAs homoepitaxial structures grown by molecular beam epitaxy is investigated in the time domain by employing a laser based picosecond ultrasound technique in...
Kasalynas, I., Seliuta, D., Simniskis, R., Tamosiunas, V., Vaicikauskas, V., Grigelionis, I., ...
A bow-tie InGaAs with broken symmetry has been designed for terahertz detection at room temperature. An active part of the detector consists of a two-dimensional electron gas which is heated...
Atmosfeer en aarde: 5 havo (2008)
Buuren, O. Van, Köhler, K., Vroon, H.
Deze lessenserie gaat over natuurkunde die nodig is om het weer, klimaat en de processen in de aardkorst en de aardkern te begrijpen. Je gaat die natuurkunde zelf toepassen op onderwerpen uit...
Optically pumped GaSb-based VECSELs (2008)
Schulz, N., Rattunde, M., Rösener, B., Manz, C., Köhler, K., Wagner, J.
We report on the current status of high-output-power optically pumped vertical-external-cavity surface-emitting lasers (VECSELs) with emission wavelengths of around 2.3 µm. The (AlGaIn)(AsSb)...
Sakowicz, M., Lusakowski, J., Karpierz, K., Grynberg, M., Knap, W., Köhler, K., ...
Detection of THz radiation by a high electron mobility (HEMT) GaAs/GaAlAs transistor was investigated at 4 K as a function of the magnetic field B. The detection signal (a source - drain photovoltage...
Infrared semiconductor lasers for DIRCM applications (2008)
Wagner, J., Schulz, N., Rösener, B., Rattunde, M., Yang, Q., Fuchs, F., ...
Köhler, K., Aguilar, F., Hensel, A., Schubert, K., Schuchmann, H.P.
ProcessNet Jahrestagung 2008, Karlsruhe, 7.-9.Oktober 2008
High Frequency Optical Rectification In Bulk GaAs And Asymmetric AlGaAs/GaAs Quantum Wells (2007)
S. Graf, H. Sigg, K. Köhler, W. Bächtold
nal transition to50# coax cables. In the case of the AQW, the incoupling of the lightis enabled via a Ge-prism placed on top of the sensitive area, Fig. 1a. In the case of the GaAs detector, the...
Advanced Optimisation of Orifice-Type High Pressure Emulsification Valves (2007)
Köhler, K., Aguilar, F., Hensel, A., Schubert, K., Schuchmann, H. P.
Yang, Q.K., Manz, C., Bronner, W., Lehmann, N., Fuchs, F., Köhler, K., ...
High peak-power operation of quaternary-barrier GaInAs/AlGaAsSb quantum-cascade lasers emitting at lambda about 3.6-3.8 µm is reported. With as-cleaved facets, the lasers (18 µm x 2.7 mm) emit a...
Epitaxial growth of GaInAs/AlGaAsSb quantum cascade lasers (2007)
Manz, C., Yang, Q.K., Kirste, L., Köhler, K.
Molecular beam epitaxial growth of quaternary barrier GaInAs/AlGaAsSb quantum cascade lasers grown lattice-matched on n-InP substrates is reported. By adjusting the As/Sb flux ratio as well as the...
Short-wavelength quantum cascade lasers (2007)
Yang, Q.K., Manz, C., Bronner, W., Köhler, K., Wagner, J.
Recent progress with quantum-cascade lasers makes them attractive sources in the important 3- to 5-µm spectral range.
Barrier- and in-well pumped GaSb-based 2.3 µm VECSELs (2007)
Wagner, J., Schulz, N., Rattunde, M., Ritzenthaler, C., Manz, C., Wild, C., ...
We report on recent advances in the performance of GaSb-based optically-pumped vertical-external-cavity surface-emitting lasers (VECSELs) emitting at wavelengths around 2.3 µm. Both barrier and...
Kunzer, M., Baeumler, M., Köhler, K., Kaufmann, U., Wagner, J.
A series of (AlGaIn)N LEDs covering the 377 to 428 nm wavelength interval has been analyzed by pulsed electro- and temperature dependent photo-luminescence with respect to the carrier density...
Baeumler, M., Kunzer, M., Schmidt, R., Liu, S., Pletschen, W., Schlotter, P., ...
UV-to-violet emitting (AlGaln)N LEDs have been investigated with respect to the temperature-dependence of the output power characteristics and non-thermal rollover of the quantum efficiency at higher...
High brightness GaSb-based optically pumped semiconductor disk lasers at 2.3 µm (2007)
Rattunde, M., Schulz, N., Ritzenthaler, C., Rösener, B., Manz, C., Köhler, K., ...
Tunable, single-frequency, diode-pumped 2.3 µm VECSEL (2007)
Maclean, A.J., Burns, D., Riis, E., Schulz, N., Rattunde, M., ...
We report high-performance single-frequency operation of a directly diode-pumped GaSb-based vertical-external-cavity surface-emitting laser (VECSEL) at 2.3 mu m. Tunability of 70nm and a maximum...
Schulz, N., Rattunde, M., Ritzenthaler, C., Rösener, B., Manz, C., Köhler, K., ...
The semiconductor heterostructure design and lasing characteristics of an optically in-well pumped (AlGaIn)(AsSb)-based vertical-external-cavity surface-emitting laser (VECSEL) emitting at 2.35 µm...
Near-UV to violet LEDs - wavelength dependence of efficiency limiting processes (2007)
Kunzer, M., Kaufmann, U., Köhler, K., Liu, S., Wagner, J.
Two wavelength series (373-435 nm) of GaInN/GaN triple quantum well LED-structures, one on sapphire and one on GaN-templates, as well as a quantum well thickness series were grown by MOVPE. In order...
Identification of point defects in Ga(Al)NAs alloys (2007)
Vorona, I.P., Mchedlidze, T., Dagnelund, D., Buyanova, I.A., Chen, W.M., Köhler, K.
By employing the optically detected magnetic resonance (ODMR) technique, two different Ga(ind i) defects, namely Ga(ind i)-A and Ga(ind i)-B, are found and identified in the investigated Ga(Al)NAs...
Schulz, N., Rattunde, M., Ritzenthaler, C., Rösener, B., Manz, C., Köhler, K., ...
In spite of elaborate heat-sinking employing intra-cavity heat-spreaders, the maximum output power of current (AlGaIn)/AsSb)-based vertical-external-cavity surface-emitting lasers (VECSELs) is still...
The two-dimensional bigradient effect and its application for GHz-THz sensing (2007)
Seliuta, D., Gruzinskis, V., Tamosiunas, V., Juozapavicius, A., Kasalynas, I., Asmontas, S., ...
A well-pronounced asymmetry in I-V-characteristics within low, 4.2-80 K, temperatures is demonstrated in asymmetrically in-plane shaped modulation-doped GaAs/AlGaAs structures. The results are...
InGaAs/AlAsSb quantum cascade detectors operating in the near infrared (2007)
Giorgetta, F.R., Baumann, E., Hofstetter, D., Manz, C., Yang, Q.K., Köhler, K., ...
The authors report on short-wavelength In0.53Ga0.47As/AlAs0.56Sb0.44 quantum cascade detectors (QCDs). At room temperature, one device detects at 505 meV (2.46 mu m) with a responsivity of 2.57 mA/W,...
Integration of In2O3 nanoparticle based ozone sensors with GaInN/GaN light emitting diodes (2007)
Cimalla, V., Kups, T., Stauden, T., Ambacher, O., ...
There is a high demand for compact low-cost ozone sensors. It has been shown recently that In2O3 nanolayers can act as ozone sensitive films activated at room temperature by ultraviolet light. In the...
Remote sensing of explosives using mid-infrared quantum cascade lasers (2007)
Fuchs, F., Wild, C., Rahmouni, Y., Bronner, W., Raynor, B., Köhler, K., ...
The spectroscopic detection of complex molecules, such as explosives, requires a much broader spectral tuning range of the employed laser compared to the well-established tunable diode laser...
Coherent acoustic phonons in phonon cavities investigated by asynchronous optical sampling (2007)
Hudert, F., Bartels, A., Janke, C., Dekorsy, T., Köhler, K.
Using a recently introduced measurement technique, called asynchronous optical sampling (ASOPS), we have investigated the dynamics of coherent acoustic phonons in a semiconductor heterostructure...
High-speed asynchronous optical sampling for high-sensitivity detection of coherent phonons (2007)
Dekorsy, T., Taubert, R., Hudert, F., Schrenk, G., Bartels, A., Cerna, R., ...
A new optical pump-probe technique is implemented for the investigation of coherent acoustic phonon dynamics in the GHz to THz frequency range which is based on two asynchronously linked femtosecond...
Soft X-ray microscopy to characterize polyelectrolyte assemblies (2007)
Köhler, K., Dejugnat, C., Dubois, M., Zemb, T., Sukhorukov, G. B., Guttmann, P., ...
Advanced Optimisation of Orifice-Type High Pressure Emulsification Valves. (2007)
Köhler, K., Aguilar, F., Hensel, A., Schubert, K., Schuchmann, H. P.
Tunable, single-frequency, diode-pumped 2.3 µm VECSEL (2007)
Maclean, A.J., Burns, D., Riis, E., Schulz, N., Rattunde, M., ...
We report high-performance single-frequency operation of a directly diode-pumped GaSb-based vertical-external-cavity surface-emitting laser (VECSEL) at 2.3 mu m. Tunability of 70nm and a maximum...
Homogenisation of dairy products at high fat content using the valve technology. (2007)
Köhler, K., Aguilar, F., Hensel, A., Schubert, K., Schuchmann, H.P.
6th European Congress of Chemical Engineering (ECCE-6), Copenhagen, DK, September 16-21, 2007
Optimisation of orifice-type high pressure emulsification valves. (2007)
Köhler, K., Aguilar, F., Hensel, A., Schubert, K., Schuchmann, H.P.
Internat.Congress on Particle Technology (PARTEC 2007), Nürnberg, March 27-29, 2007
Köhler, K., Aguilar, F., Hensel, A., Schubert, K., Schubert, H., Schuchmann, H.P.
Chemical Engineering and Technology, 30(2007) S.1590-95
Coherent acoustic phonons in nanostructures investigated by asynchronous optical sampling (2006)
Dekorsy, T., Hudert, F., Cerna, R., Schäfer, H., Janke, C., Bartels, A., ...
A new optical pump-probe technique is implemented for the investigation of acoustic phonon dynamics in the GHz to THz frequency range which is based on two asynchronously linked femtosecond lasers....
X-ray topographic imaging of (AI,Ga)N/GaN based electronic device structures on SiC (2006)
Kirste, L., Müller, S., Kiefer, R., Quay, R., Köhler, K., Herres, N.
Structural defects and their impact on the performance, lifetime and reliability of electronic devices are of permanent interest for crystal growers and device manufacturers. This is especially true...
Fuchs, F., Kirn, B., Mann, C., Yang, Q.K., Bronner, W., Raynor, B., ...
We present a study of the spectral characteristics of Fabry-Perot quantum cascade lasers in pulsed mode operation applying a time resolution of 3 ns in combination with a high spectral resolution of...
GaSb-based VECSELs emitting at around 2.35 µm employing different optical pumping concepts (2006)
Schulz, N., Rattunde, M., Manz, C., Köhler, K., Wild, C., Wagner, J., ...
We report on the characteristics of (AlGaIn)(AsSb)-based optically pumped vertical-external-cavity surface-emitting lasers (VECSELs) emitting at wavelengths around 2.35 µm. For barrier-pumped...
Kirste, L., Müller, S., Kiefer, R., Quay, R., Köhler, K., Herres, N.
Structural defects and their impact on the performance of electronic devices are of permanent interest for crystal growers and device manufacturers. This is especially true for epitaxial...
Ultrafast fiske effect in semiconductor superlattices (2006)
Kosevich, Y.A., Hummel, A.B., Roskos, H.G., Köhler, K.
The current flowing across a semiconductor superlattice in tilted electric and magnetic fields is known to exhibit resonant enhancement, when Landau states of neighboring wells align at certain...
Optically pumped GaSb-based VECSEL emitting 0.6 W at 2.3 µm (2006)
Schulz, N., Rattunde, M., Manz, C., Köhler, K., Wild, C., Wagner, J., ...
We report on the operation and beam profile analysis of an optically pumped GaSb-based vertical-external-cavity surface-emitting laser at 2.33 µm. To compensate for the low thermal conductivity of...
Optically detected magnetic resonance studies of point defects in Ga(Al)NAs (2006)
Vorona, I.P., Mchedlidze, T., Dagnelund, D., Buyanova, I.A., Chen, W.M., Köhler, K.
An optically detected magnetic resonance (ODMR) study of Ga(Al)NAs alloys grown by molecular beam epitaxy on GaAs substrates is presented. A number of grown-in defects were observed which act as...
Mg doping profile in III-N light emitting diodes in close proximity to the active region (2006)
Köhler, K., Perona, A., Maier, M., Wiegert, J., Kunzer, M., Wagner, J.
We have investigated how in (AlGaIn)N quantum well (QW) light emitting diodes, grown by low-pressure metal-organic vapor phase epitaxy, the actual Mg doping profile close to the interface between...
Mann, C., Yang, Q.K., Fuchs, F., Bronner, W., Köhler, K., Wagner, J.
The influence of injector doping concentration N(inj) on the performance of InP-based quantum-cascade (QC) lasers is investigated for devices emitting around 9.2-µm wavelength and injector doping...
High power continuous wave operation of a GaSb-based VECSEL emitting near 2.3 µm (2006)
Schulz, N., Rattunde, M., Manz, C., Köhler, K., Wild, C., Wagner, J., ...
We report on a GaSb-based optically pumped vertical external cavity surface-emitting laser (VECSEL) operating near 2.3 µm. The epitaxial layer structure has been analyzed by high-resolution X-Ray...
Bartels, A., Hudert, F., Janke, C., Dekorsy, T., Köhler, K.
We demonstrate a technique for femtosecond time-resolved optical pump-probe spectroscopy that allows to scan over a nanosecond time delay at a kilohertz scan rate without mechanical delay line. Two...
Distributed-feedback GaInAs/AIAsSb quantum-cascade lasers operating at 300 K (2006)
Yang, Q.K., Bronner, W., Manz, C., Raynor, B., Menner, H., Mann, C., ...
Short-wavelength (lambda about 4 µm) single-mode distributed-feedback GaInAs/AlAsSb quantum-cascade lasers operating in pulsed mode up to room temperature (300 K) have been demonstrated by etching...
Güngerich, M., Klar, P.J., Heimbrodt, W., Volz, K., Köhler, K., Wagner, J., ...
We present comprehensive optical studies of a series of as-grown and hydrogenated Ga(0.95)Al(0.05)As(1-x)N(x) epitaxial layers with various amounts x of substitutional nitrogen. Photomodulated and...
Above room-temperature GaInAs/Al(Ga)AsSb quantum cascade lasers (2006)
Yang, Q.K., Manz, C., Bronner, W., Köhler, K., Wagner, J.
High-temperature (up to at least 400 K) pulsed-mode operation of quantum cascade (QC) lasers based on GaInAs/Al(Ga)AsSb grown lattice-matched on InP substrates are presented in this article. The...
Yang, Q.K., Manz, C., Bronner, W., Köhler, K., Wagner, J.
We discuss the possible limitations on realizing short-wavelength GaInAs/AlAsSb quantum-cascade lasers and consequently demonstrate room-temperature (T(ind max) = 310 K) short-wavelength (lambda...
Kosevich, Y.A., Hummel, A.B., Roskos, H.G., Köhler, K.
The coherent coupling between electron Bloch and in-plane cyclotron oscillations in semiconductor superlatttices in tilted electric and magnetic fields induces a unidirectional quasi-DC current in...
Lisauskas, A., Blöser, C., Sachs, R., Demarina, N.V., Juozapavicius, A., Valusis, G., ...
We report on experiment and theory of the evolution of the electric field in undoped GaAs/AlGaAs semiconductor superlattices subjected to femtosecond optical excitation. We performed time-resolved...
Seliuta, D., Kasalynas, I., Tamosiunas, V., Balakauskas, S., Martunas, Z., Asmontas, S., ...
A passive detection scheme for broadband, 10 GHz-2.52 THz, sensing at room temperature is demonstrated using a hemispherical silicon lens-coupled diode of an asymmetrically-shaped bow-tie geometrical...
New trends in terahertz electronics: Review (2006)
Tamosiunas, V., Seliuta, D., Juozapavicius, A., Sirmulis, E., Valusis, G., El Fatimy, A., ...
Yang, Q.K., Manz, C., Bronner, W., Schäuble, K., Mann, C., Schwarz, K., ...
Short-wavelength (lambda < 4 µm) GaInAs-AlAsSb quantum cascade (QC) lasers have been demonstrated using a "bound-to-continuum" design for the purpose of reducing the electric injection power...
Salt-induced swelling-to-shrinking transition in polyelectrolyte multilayer capsules (2006)
Köhler, K., Biesheuvel, P. M., Weinkamer, R., Möhwald, H., Sukhorukov, G. B.
Effect of microwave radiation on polymer microcapsules containing inorganic nanoparticles (2006)
Gorin, D. A., Shchukin, D. G., Mikhailov, A. I., Köhler, K., Sergeev, S. A., Portnov, S. A., ...
Laser-induced release of encapsulated materials inside living cells (2006)
Skirtach, A. G., Javier, A. M., Kreft, O., Köhler, K., Alberola, A. P., Möhwald, H., ...
Coherent acoustic phonons in nanostructures investigated by asynchronous optical sampling (2006)
Dekorsy, Thomas, Hudert, Florian, Cerna, Roland, Schaefer, Hanjo, Janke, Christof, Bartels, Albrecht, ...
A new optical pump-probe technique is implemented for the investigation of acoustic phonon dynamics in the GHz to THz frequency range which is based on two asynchronously linked femtosecond lasers....
Development of a microstructured system for improved partial homogenisation. (2006)
Aguilar, F.A., Hensel, A., Köhler, K., Schuchmann, H.P., Schubert, H., Schubert, K.
4eme Congres Mondial de L'Emulsion, Lyon, F, 3-6 Octobre, 2006 (Poster)
The evolution of the electric field in an optically excited semiconductor superlattice (2005)
Lisauskas, A., Blöser, C., Hummel, A.B., Sachs, R., Roskos, H.G., Juozapavicius, A., ...
We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al(0.3)Ga(0.7)As superlattice subsequent to femtosecond optical excitation. Information on the spatio-temporal evolution of...
THz/subTHz detection by asymmetrically-shaped bow-tie diodes containing 2DEG Layer (2005)
Seliuta, D., Tamosiunas, V., Sirmulis, E., Asmontas, S., Suziedelis, A., Gradauskas, J., ...
We present asymmetrically-shaped bow-tie diodes based on a modulation-doped GaAs/AlGaAs structure. One of the bow-tie leaves is metallized in order to concentrate the incident radiation into the apex...
Electro-optic investigation of the Coherent Hall Effect in semiconductor superlattices (2005)
Hummel, A.B., Blöser, C., Bauer, T., Roskos, H.G., Kosevich, Y., Köhler, K.
After the first observation of the Coherent Hall Effect in a GaAs/Al(0.3)Ga(0.7)As superlattice by means of THz-emission spectroscopy, the dynamics of impulsively excited electron wavepackets in...
Köhler, K., Stephan, T., Perona, A., Wiegert, J., Maier, M., Kunzer, M., ...
The influence of the Mg doping profile on the electroluminescence (EL) efficiency of (AlGaIn)N quantum well (QW) light-emitting diodes, grown by low-pressure metal-organic vapor-phase epitaxy on...
Einmodige Quantenkaskadenlaser für Anwendungen in der Spurenanalytik (2005)
Mann, C., Yang, Q.K., Bronner, W., Köhler, K., Wagner, J.
Single-mode DFB quantum cascade lasers for applications in trace-gas sensing were designed, fabricated, and characterized. The devices can be applied for the detection of the fundamental...
Bonding of nitrogen in dilute InAsN and high In-content GaInAsN (2005)
Wagner, J., Köhler, K., Ganser, P., Maier, M.
Dilute InAs(1-y)N(y) and high In-content Ga(1-x)In(x)As(1-y)N(y) layers with y lt = 0.012 and x gt= 0.92 were grown by rf-nitrogen plasma source molecular-beam epitaxy on InP substrates using a...
Lisauskas, A., Blöser, C., Sachs, R., Roskos, H.G., Juozapavicius, A., Valusis, G., ...
We apply time-resolved photocurrent and differential electroreflectance spectroscopy to study the evolution of the internal field in a GaAs/ AlGaAs superlattice after pulsed optical excitation at low...
Yang, Q.K., Mann, C., Fuchs, F., Köhler, K., Bronner, W.
Conventional strain-compensated quantum cascade (QC) lasers are fabricated with both tensile. strained AlInAs and compressively strained GaInAs layers. We show that strain compensation can also be...
Lisauskas, A., Blöser, C., Sachs, R., Roskos, H.G., Juozapavicius, A., Valusis, G., ...
We report on photocurrent spectroscopy on undoped GaAs/AlGaAs semiconductor superlattices subjected to femtosecond optical excitation. The evolution of the carrier-drift-induced inhomogeneity of the...
Müller, S., Köhler, K., Kiefer, R., Quay, R., Baeumler, M., Kirste, L.
Heterostructures of GaN/AlGaN for power applications are grown by metal organic vapor phase epitaxy in a multiwafer reactor on sapphire and SiC substrates. The insulating properties of the GaN buffer...
Baeumler, M., Müller, S., Köhler, K., Wagner, J.
AlGaN/GaN heterostructures for power applications, grown on sapphire substrates by metal organic vapor phase epitaxy (MOVPE) in a multiwafer reactor were analyzed by spectroscopic ellipsometry (SE)....
Manz, C., Yang, Q.K., Köhler, K., Maier, M., Kirste, L., Wagner, J., ...
Short wavelength (lambda < 5 mu m) quantum cascade lasers are of current interest as they operate in the technologically important atmospheric 3-5 mu m transparency window. For this wavelength range...
Violet-emitting diode lasers on low defect density GaN templates (2005)
Sommer, F., Vollrath, F., Kunzer, M., Pletschen, W., Müller, S., Köhler, K., ...
We compare the electro-optical characteristics of violet-emitting ridge waveguide (AlGaIn)N quantum well diode lasers with etched laser facets, grown on GaN templates with a homogeneously reduced...
GaInAs/AlAsSb quantum-cascade lasers operating up to 400 K (2005)
Yang, Q.K., Manz, C., Bronner, W., Mann, C., Kirste, L., Köhler, K., ...
Above room-temperature (T>=400 K) operation of GaInAs/AlAsSb-based quantum-cascade lasers has been demonstrated. The lasers are based on vertical-transition active regions and consist of 25 periods...
GaInAs/AlGaAsSb quantum-cascade lasers (2005)
Yang, Q.K., Manz, C., Bronner, W., Kirste, L., Köhler, K., Wagner, J.
Quaternary-barrier-containing GaInAs/A1GaAsSb quantum-cascade lasers, motivated by reducing the barrier height compared to that in GaInAs/A1AsSb quantum-cascade lasers, have been demonstrated. The...
Broad band THz sensing by 2DEG bow-tie-type diodes (2005)
Valusis, G., Seliuta, D., Tamosiunas, V., Sirmulis, E., Balakauskas, S., Gradauskas, J., ...
We suggest a novel approach to detect broad band, 0.078-2.52 THz, electromagnetic radiation at room temperature using an asymmetrically-shaped bow-tie diode based on a modulation-doped GaAs/AlGaAs...
Asmontas, S., Juozapavicius, A., Seliuta, D., Sirmulis, E., Tamosiunas, V., Valusis, G., ...
The terahertz (THz) frequency band which lies between those of microwaves (exploited in mobile phones, satellite communications, television) and the infrared, is becoming increasingly important in a...
High duty-cycle (>= 50%) operation of GaInAs/Al(Ga)AsSb quantum cascade lasers (2005)
Bronner, W., Yang, Q.K., Manz, C., Kaufel, G., Mann, C., Köhler, K., ...
Molecular beam epitaxy grown GaInAs/Al(Ga)AsSb heterostructures, offering conduction band offsets (gamma-valley) of >= 1 eV, appear to be the prime candidates for realizing high-performance...
Continuous-wave operation of GaInAs/AlGaAsSb quantum cascade lasers (2005)
Yang, Q.K., Bronner, W., Manz, C., Moritz, R., Mann, C., Kaufel, G., ...
We report on the demonstration of continuous-wave (CW) operation of GaInAs-AlGaAsSb quantum cascade (QC) lasers. By placing a 2.5-µm-thick gold layer on both sides of the laser ridge to extract heat...
Improved GaN layer morphology by hydride vapor phase epitaxy on misoriented Al(2)O(3) wafers (2005)
Scholz, F., Brueckner, P., Habel, F., Peter, M., Köhler, K.
Crack-free thick GaN layers have been grown by hydride vapor phase epitaxy on on-axis as well as on off-axis GaN-Al2O3 templates. A dramatic difference in surface quality could be traced back to the...
Melting of PDADMAC/PSS capsules investigated with AFM force spectroscopy (2005)
Mueller, R., Köhler, K., Weinkamer, R., Sukhorukov, G., Fery, A.
III-N based short-wavelength LEDs, LUCO-LEDs and lasers (2004)
Sommer, F., Stephan, T., Vollrath, F., Köhler, K., Kunzer, M., Müller, S., ...
Results are presented on the effect of using GaN templates with homogeneously reduced defect density on the performance of violet- und UV-emitting (AlGaIn)N LEDs, as well as on the use of such LED...
Epitaxy and characterisation of dilute III-As(1-y)N(y) on GaAs and InP (2004)
Köhler, K., Wagner, J., Ganser, P., Serries, D., Geppert, T., Maier, M., ...
Epitaxial growth and characterisation of Ga(1-x)In(x)As(1-y)N(y) films and quantum wells are presented. Starting with the epitaxy on GaAs, recent results on the local bonding of nitrogen in...
Room-temperature intersubband emission from GaInAs-AlAsSb quantum cascade structure (2004)
Yang, Q.K., Manz, C., Bronner, W., Köhler, K., Wagner, J.
Room-temperature (300 K) intersubband electroluminescence has been obtained from a quantum cascade structure adopting triple-well vertical-transition active regions, based on...
Optical and acoustic intersubband plasmons (2004)
Rösch, M., Batke, E., Köhler, K., Ganser, P.
Intersubband plasmon modes in a tunneling coupled bilayer system based on a 40nm wide GaAs/Al(0.3)Ga(0.7)As double heterostructure are studied by grating-coupler-assisted far-infrared spectroscopy....
Detection of terahertz/sub-terahertz radiation by asymmetrically-shaped 2DEG layers (2004)
Seliuta, D., Sirmulis, E., Tamosiunas, V., Balakauskas, S., Asmontas, S., Suziedelis, A., ...
A diode structure to detect THz/subTHz radiation based on an MBE-grown modulation-doped GaAs/Al(0.25)Ga(0.75)As structure is proposed. Devices have an asymmetrically-shaped geometrical from in the...
The realization of long-wavelength (lambda (2004)
Köhler, K., Wagner, J., Ganser, P., Serries, D., Geppert, T., Maier, T., ...
The epitaxial growth and characterization of dilute Ga(1-x)In(x)As(1-y)N(y) films and quantum wells are presented. Starting with the epitaxy on GaAs, recent results on the local bonding of nitrogen...
Wagner, J., Serries, D., Köhler, K., Ganser, P., Maier, M., Kirste, L., ...
We report on the growth and characterization of high In-content quaternary Ga(1-x)In(x)As(1-y)N(y) (0.78 lt = x lt = 1,y lt = 0.02), grown by plasma assisted molecular beam epitaxy on InP-substrates....
Stephan, T., Köhler, K., Maier, M., Kunzer, M., Schlotter, P., Wagner, J.
The influence of the Mg doping profile on the electroluminescence efficiency of GaInN light emitting diodes (LED) has been investigated. The Mg doping profile is influenced by segregation as well as...
Microwave sensor based on modulation-doped GaAs/AlGaAs structure (2004)
Juozapavicius, A., Ardaravicius, L., Suziedelis, A., Kozic, A., Gradauskas, J., Kundrotas, J., ...
We propose a microwave diode based on a modulation-doped GaAs/Al(0.25)Ga(0.75)As structure. The principle of the diode operation relies on a non-uniform heating of the two-dimensional electron gas in...
Wave-function reconstruction in a graded semiconductor superlattice (2004)
Lyssenko, V.G., Hvam, J.M., Meinhold, D., Köhler, K., Leo, K.
We reconstruct a 'test' wave function in a strongly coupled, graded well-width superlattice by resolving the spatial extension of the interband polarisation and deducing the wave function employing...
Single-mode InP-based quantum cascade lasers for applications in trace-gas sensing (2004)
Mann, C., Yang, Q.K., Fuchs, F., Bronner, W., Köhler, K., Beyer, T., ...
Intraband coherence of bloch oscillations after momentum scattering (2004)
Nüsse, S., Wolter, F., Haring Bolivar, P., Köhler, K., Hey, R., Grahn, H.T., ...
Resonantly excited secondary emission of light (RSE) in GaAs/AlGaAs superlattices gives a direct proof for the stability of coherent Bloch dynamics beyond the optical coherent regime. The...
Essential cysteine residues of the type IIa Na+/Pi cotransporter. (2003)
Köhler, K, Forster, I C, Stange, G, Biber, Jürg, Murer, H
The rat renal Na(+)/P(i) cotransporter (NaP(i)-IIa) contains 12 native cysteines. When individually replaced by a serine, none appears essential for proper expression and function. Nevertheless, the...
New results on high-field transport in semiconductor superlattices (2003)
Holfeld,C.P., Rosam,B., Meinhold,D., Glutsch,S., Schäfer,W., Zhang,J., ...
Quantum Cascade lasers for the Mid-Infrared Spectral Range: Devices and Applications (2003)
Mann, C., Yang, Q. K., Fuchs, F., Bronner, W., Kiefer, R., Köhler, K., ...
Epitaxial growth and device fabrication of GaN based electronic and optoelectronic structures (2003)
Müller, S., Quay, R., Sommer, F., Vollrath, F., Kiefer, R., Köhler, K., ...
At the Fraunhofer IAF both single and multiwafer low-pressure MOVPE reactors are used for the growth of a) GaN/AlGaN layer sequences for the fabrication of high electron mobility transistors (HEMTs)...
Hybrid integrated optical receivers for high-speed data transmission (2003)
Leich, M., Hurm, V., Berger, J., Dietrich, E., Sohn, J., Leuther, A., ...
Flip-chip-mounting of integrated circuits has been shown as an effective way to connect integrated circuits with substrates providing highest bandwidths. This technique also has been used to connect...
Kiefer, R., Quay, R., Müller, S., Feltgen, T., Raynor, B., Schleife, J., ...
The suitability of AlGaN/GaN HEMTs on SiC is discussed with respect to mm-wave applications at 40 GHz and beyond. A 0.15 µm T-gate AlGaN/GaN-HEMT 2-inch technology on SiC and sapphire was developed...
Quenching of transient photoluminescence by strong in-plane electric fields in quantum wells (2003)
Kundrotas, J., Dargys, A., Asmontas, S., Gintaras, V., Köhler, K.
Investigations of transient photoluminescence induced by external electric fields parallel to the layers of GaAs/Al0.35Ga0.65As quantum wells are reviewed. The photoluminescence was detected by...
Stephan, T., Köhler, K., Kunzer, M., Schlotter, P., Wagner, J.
The influence of the Mg doping profile on the luminescence performance of InGaN light emitting diodes with an emission wavelength of 395 nm has been investigated. An increased spread of the Mg doping...
THz dielectric response of a moving electron gas (2003)
Sachs, R., Banyai, L., Mohler, E., Köhler, K., Roskos, H.G.
We measured the time-resolved transmission of picosecond terahertz pulses through a modulation-doped Al(0.3)Ga(0.7)As/GaAs heterojunction in the presence of a D.C. current. The introduction of a...
Quantitative assessment of Al-to-N bonding in dilute Al(0.33)Ga(0.67)As(1-y)N(y) (2003)
Wagner, J., Geppert, T., Köhler, K., Ganser, P., Maier, M.
A quantitative assessment of the group III-nitrogen bonding in low N-content Al(0.33)Ga(0.67)As(1-y)N(y)with y
New results on high-field transport in semiconductor superlattices (2003)
Holfeld, C.P., Rosam, B., Meinhold, D., Glutsch, S., Schäfer, W., Zhang, J., ...
The optical properties of an electrically biased semiconductor superlattice are strongly influenced by coupling to other bands. As these coupling mechanisms depend on the strength of the applied...
The Hall current of coherent electron wavepackets (2003)
Bauer, T., Hummel, A.B., Kolb, J.S., Roskos, H.G., Kosevich, Y., Köhler, K.
Terahertz-emission spectroscopy reveals two regimes of the Hall current of impulsively excited coherent charge-carrier wavepackets in a GaAs/AlGaAs superlattice as a function of the electric and...
Continuous-wave operation of 5 µm quantum cascade lasers with high-reflection coated facets (2003)
Mann, C., Yang, Q.K., Fuchs, F., Bronner, W., Köhler, K.
A report is presented on the continuous-wave operation of lambda approximately=5 mu m GaInAs/AlInAs/InP-based quantum cascade lasers up to a heatsink temperature of 222 K (-51 degrees C). The devices...
Bauer, T., Kolb, J.S., Hummel, A.B., Roskos, H.G., Kosevich, Y., Köhler, K.
The Coherent Hall Effect denotes the transient current/voltage Hall response of impulsively excited coherent charge-carrier wavepackets in a solid. We studied this effect by THz-emission spectroscopy...
Asymmetrically - shaped diodes for microwave - submillimeter sensing (2003)
Asmontas, S., Ardavicius, L., Balakauskas, S., Gradauskas, J., Kozic, A., Kundrotas, J., ...
We present a concept and possible applications of asymmetrically-shaped diodes fabricated from different types of semiconductors, i.e. non-uniform GaAs, n-Si and modulation-doped...
AlGaN/GaN HEMTs on silicon carbide substrates for microwave power operation (2003)
Lossy, R., Chaturvedi, N., Heymann, P., Köhler, K., Müller, S., Würfl, J.
Results from technology and microwave characterization of large periphery AlGaN/GaN power HEMTs on insulating SiC substrates are presented. The influence of processing steps on device performance is...
Hummel, A.B., Bauer, T., Roskos, H.G., Glutsch, S., Köhler, K.
We present experimental and theoretical photocurrent spectra of a GaAs/AlGaAs superlattice under the influence of electric and magnetic fields parallel to the growth axis. In this field...
Quantum cascade lasers for the mid-infrared spectral range: Devices and applications (2003)
Mann, C., Yang, Q.K., Fuchs, F., Bronner, W., Kiefer, R., Köhler, K., ...
Quantum cascade lasers emitting at lambda about 5 µm based on different active region designs are investigated. Using lattice-matched GaInAs/ AlInAs on InP substrates the maximum peak optical power...
Multiwafer epitaxy of GaN/AlGaN heterostructures for power applications (2003)
Köhler, K., Müller, S., Rollbühler, N., Kiefer, R., Quay, R., Weimann, G.
Heterostructures of GaN/AlGaN for power applications are grown by metal organic vapor phase epitaxy in a multiwafer reactor on sapphire and SiC substrates. Electrical properties of the...
Mid-infrared quantum cascade lasers operation above room temperature (2003)
Yang, Q.K., Mann, C., Fuchs, F., Kiefer, R., Köhler, K., Schneider, H.
Above room-temperature operation of lambda about 5 µm quantum cascade lasers with three different active regions is reported. Comparison between the three different designs, namely the conventional...
Rosam, B., Leo, K., Glück, M., Keck, F., Korsch, H.J., Zimmer, F., ...
For high electric fields, the lifetime of Wannier-Stark ladder states in a periodic potential is reduced by the fundamental process of Zener tunneling. We report on the analysis of the coherence...
Terahertz optical properties of thin doped contact layers in GaAs device structures (2003)
Bauer, T., Kolb, J.S., Mohler, E., Roskos, H.G., Köhler, K.
We investigate the transmittance of thin doped GaAs layers in the terahertz (THz) frequency range taking into account multiple reflections. Our experimental and theoretical study aims at providing a...
Serries, D., Geppert, T., Köhler, K., Ganser, P., Wagner, J.
Recent results on the local bonding of nitrogen in dilute GaInAsN and AlGaAsN on GaAs are reviewed, revealing that bonding of nitrogen in GaInAsN is controlled by an interplay between bond cohesive...
SIMS depth profiling of InGaAsN/InAlAs quantum wells on InP (2003)
Maier, M., Serries, D., Geppert, T., Köhler, K., Güllich, H., Herres, N.
Quaternary InxGa1-xAsyN1-y (x > 0.53, 1 - y
Bonding of nitrogen in dilute GaInAsN and AlGaAsN studied by Raman spectroscopy (2003)
Wagner, J., Geppert, T., Köhler, K., Ganser, P., Maier, M.
To gain information on the local bonding of the nitrogen, Ga1-xInxAs1-yNy with x
New results on high-field transport in semiconductor superlattices (2003)
Holfeld, C.P., Rosam, B., Meinhold, D., Glutsch, S., Schäfer, W., Zhang, J., ...
Kim, M.A., Priemyschev, A., Panak, P.J., Yun, J.I., Kim, J.I., Köhler, K.
Jahrestagung der GDCh-Fachgruppe Nuklearchemie, München, 7.-10.Oktober 2003
Köhler, K, Forster, I C, Stange, G, Biber, Jürg, Murer, H
Two highly similar regions in the predicted first intracellular (ICL-1) and third extracellular loop (ECL-3) of the type IIa Na+/P(i) cotransporter (NaPi-IIa) have been shown previously to contain...
Forster, I C, Köhler, K, Biber, Jürg, Murer, H
Electrogenic cotransporters are membrane proteins that use the electrochemical gradient across the cell membrane of a cosubstrate ion, for example Na(+) or H(+), to mediate uphill cotransport of a...
Functional studies on a split type II Na/P(i)-cotransporter. (2002)
Ehnes, C, Forster, I C, Köhler, K, Biber, J, Murer, H
Analysis of rat and mouse proximal tubular brush-border membrane expression of the type IIa Na/P(i)-cotransporter provides evidence for its cleavage in the large extracellular loop (ECL-2). To study...
Forster, I C, Köhler, K, Stange, G, Biber, J, Murer, H
The effects of the arginine-modifying reagent phenylglyoxal on the kinetics of the type IIa Na + /Pi cotransporter expressed in Xenopus, oocytes were studied by means of 32Pi uptake and...
The renal type IIa Na/Pi cotransporter: structure-function relationships. (2002)
Murer, H, Köhler, K, Lambert, G, Stange, G, Biber, Jürg, Forster, I C
The type IIa Na/Pi cotransporter mediates proximal tubular brush-border membrane secondary active phosphate (Pi) flux. It is rate limiting in tubular Pi reabsorption and, thus, a final target in many...
Zener tunneling in superlattices in a magnetic field (2002)
Meinhold, D., Leo, K., Fromer, N.A., Chemla, D.S., Glutsch, S., Bechstedt, F., ...
We present a study of the Zener effect in the optical absorption of strongly coupled superlattices with both a magnetic and an electric field in growth direction. The in-plane continuum of electron...
Importance of nonradiative recombination process in violet UV InGaN light emmitting diodes (2002)
Stephan, T., Kunzer, M., Schlotter, P., Pletschen, W., Obloh, H., Müller, S., ...
The influence of nonradiative recombination processes on the output power P of InGaN light emitting devices (LEDs) with emission wavelength between 380 and 430 nm grown on sapphire substrates have...
Leich, M., Hurm, V., Sohn, J., Feltgen, T., Bronner, W., Köhler, K., ...
Hybrid integrated photoreceivers with up to 65 GHz bandwidth are presented. They consist of GalnAs/AlGalnAs/AlInAs multimode waveguide photodiodes, flip-chip bonded on GaAs-based pseudomorphic HEMT...
Sohn, J., Leven, A., Hurm, V., Walcher, H., Benz, W., Ludwig, M., ...
High conversion gain photoreceivers for broad-band (40 Gbit/s) and narrow-band (10 GHz) applications were manufactured using GaAs-based pseudomorphic HEMT (pHEMT) amplifiers. The photoreceivers...
AlGaN/GaN-HEMTs for power applications up to 40 GHz (2002)
Kiefer, R., Quay, R., Müller, S., Köhler, K., Van Raay, F., Raynor, B., ...
A 0.15 µm T-gate AlGaN/GaN-HEMT 2-inch technology has been developed. Transistors with 120 µm gatewidth show a peak transconductance of 300 mS/mm and cut-off frequencies f(ind t) and f(ind max) of...
Quantum cascade lasers with blocking barriers in the active regions (2002)
Mann, C., Yang, Q.K., Fuchs, F., Kiefer, R., Köhler, K., Schneider, H.
Large area AlGaN/GaN HEMTs grown on insulating silicon carbide substrates (2002)
Lossy, R., Chaturvedi, N., Würfl, J., Müller, S., Köhler, K.
Large periphery Al(0.25)Ga(0.75)N/GaN-HEMTs on SiC-substrates are fabricated on a 2-inch process line using stepper lithography. DC characteristics reveal current densities above 1,2 A/mm and...
Herres, N., Kirste, L., Obloh, H., Köhler, K., Wagner, J., Koidl, P.
An extension of Bond's method for determining precision lattice parameters serves to determine the lattice parameters of (strained) unit cells of a film from the peak positions of the film alone. We...
Single chip white LEDs: Weiße Einzelchip-LEDs (2002)
Kaufmann, U., Kunzer, M., Köhler, K., Obloh, H., Pletschen, W., Schlotter, P., ...
The operation principles of the various single chip luminescence conversion (LUCO) white LEDs, that can be realized with blue or ultraviolet (UV) LED chips, are briefly reviewed. In order to...
Quaternary GaInAsN with high In content: Dependence of band gap energy on N content (2002)
Serries, D., Geppert, T., Ganser, P., Maier, M., Köhler, K., Herres, N., ...
Quaternary pseudomorphically strained GaInAsN films and double-quantum wells were grown by plasma assisted molecular-beam epitaxy on an InP substrate. The In content ranged from 53% to 70% while the...
GHz-THz detection by asymmetrically-shaped GaAs: Bulk material versus nanostructures (2002)
Valusis, G., Sachs, R., Roskos, H.G., Suziedelis A., Gradauskas, J., Asmontas, S., ...
This communication presents experimental study of the asymmetrically-shaped bulk GaAs and modulation-doped GaAs/Al0.25Ga0.75As structures as active parts of detectors of electromagnetic radiation in...
Wagner, J., Kaufmann, U., Köhler, K., Kunzer, M., Pletschen, W., Obloh, H., ...
We report on the development of (AlGaIn)N quantum well LEDs covering the 380 to 430 nm wavelength range, which serve as the primary light source for tri-phosphor luminescence conversion white LEDs....
Serries, D., Geppert, T., Ganser, P., Köhler, K., Wagner, J.
Quaternary pseudomorphically strained Ga(1-x)In(x)As(1-y)N(y) films and double quantum wells (0.53
Hurm, V., Bronner, W., Benz, W., Köhler, K., Lösch, R., ...
At 1 x 12 metal-semiconductor-metal (MSM) photodiode array operating at 10 Gbit/s per channel was developed for short-haul 0.85 µm wavelength parallel optical links. The GaAs-based MSM photodiodes...
Yang, Q.K., Mann, C., Fuchs, F., Kiefer, R., Köhler, K., Rollbühler, N., ...
We report the improvement of quantum cascade lasers emitting at lambda ~5 mu m by introducing AlAs blocking barriers together with strain- compensating InAs layers into the active regions. The...
Preferential formation of Al-N bonds in low N-content AlGaAsN (2002)
Geppert, T., Wagner, J., Köhler, K., Ganser, P., Maier, M.
The bonding of nitrogen in low N-content Al(x)Ga(1-x)As(1-y)N(y) with x
Meinhold, D., Rosam, B., Löser, F., Lyssenko, V.G., Rossi, F., ...
We investigate the dynamics of a Bloch-oscillating wave packet in the presence of strong coupling to delocalized above barrier states (Zener tunneling), using time-resolved intraband...
Coherent hall effect in a semiconductor superlattice (2002)
Bauer, T., Kolb, J., Hummel, A.B., Roskos, H.G., Kosevich, Y., Köhler, K.
The coherent Hall effect denotes the transient Hall response of impulsively excited coherent charge-carrier wave packets in a solid. We report the first experimental study of this phenomenon (i)...
Lambert, G, Forster, I C, Stange, G, Köhler, K, Biber, J, Murer, H
The transport function of the rat type IIa Na(+)/P(i) cotransporter is inhibited after binding the cysteine modifying reagent 2-aminoethyl methanethiosulfonate hydrobromide (MTSEA) to a cysteine...
Traebert, M, Köhler, K, Lambert, G, Biber, J, Forster, I C, Murer, H
We have combined a functional assay, surface labeling and immunocytochemical methods to compare total and surface-exposed renal type IIa Na+/Pi cotransporter protein. The wild-type type cotransporter...
Nonlinear transport in superlattices: Bloch oscillations and Zener breakdown (2001)
Löser, F., Rosam, B., Meinhold, D., Lyssenko, V.G., Sudzius, M., Dignam, M.M., ...
Semiconductor superlattices have been intensively used as a model system for the investigation of high field transport in solids. Here, we discuss ultrafast optical experiments which allow us to...
Fano resonances in semiconductor superlattices (2001)
Canzler, T.W., Holfeld, C.P., Löser, F., Lyssenko, V.G., Leo, K., Whittaker, D.M., ...
We use semiconductor superlattices as a model system for the investigation of Fano resonances. In absorption the excitonic transitions of the Wannier-Stark ladder show the typical asymmetric line...
Alpha particle induced luminescence from multiple quantum wells (2001)
Kundrotas, J., Dargys, A., Granja, C., Köhler, K., Pospísil, S., Remeikis, V., ...
The luminescence induced by alpha particles in GaAs/Al(0.35)Ga(0.65)As multiple quantum well (MQW) semiconductor was detected and investigated. The luminescence was observed at liquid nitrogen and at...
Sohn, J., Leven, A., Hurm, V., Walcher, H., Benz, W., Kuri, M., ...
The photoreceiver is a key component for microwave fiber optic links and optoelectronic generation of microwave and millimeter-wave in phased array antennas for radar systems. The narrow-band...
N-induced vibrational modes in GaAsN and GaInAsN studied by resonant Raman scattering (2001)
Wagner, J., Geppert, T., Köhler, K., Ganser, P., Herres, N.
Vibrational modes introduced by the incorporation of N into GaAs and GaInAs have been studied by Raman spectroscopy on samples grown by molecular-beam epitaxy using a rf nitrogen plasma source. When...
Ultraviolet pumped tricolor phosphor blend white emitting LEDs (2001)
Kaufmann, U., Kunzer, M., Köhler, K., Obloh, H., Pletschen, W., Schlotter, P., ...
Near-UV and violet emitting AlGaInN single quantum well LED structures were grown by MOCVD on sapphire substrates. On-wafer tests before processing gave an output power at 40 mA between 1.4 mW at 380...
Kundrotas, J., Dargys, A., Valusis, G., Asmontas, S., Köhler, K., Leroy, C.
Multiple quantum well (MQW) samples grown by the molecular beam epitaxy method were irradiated by alpha particles from isotope 239.Pu. The photoluminescence (PL) spectra and PL integrated intensity...
Changes of MQW photoluminescence under alpha particle irradiation (2001)
Kundrotas, J., Dargys, A., Valusis, G., Asmontas, S., Granja, C., Pospisil, S., ...
Undoped multiple quantum well (MQW) samples grown by the molecular beam epitaxy method were irradiated by 5.15 MeV energy alpha particles. A strong influence of irradiation on the photoluminescence...
Filling-factor-dependent electron correlations observed in cyclotron resonance (2001)
Manger, M., Batke, E., Hey, R., Friedland, K.J., Köhler, K., Ganser, P.
Cyclotron resonances of electron space-charge layers in GaAs were studied at 3.He temperatures covering a density regime from 2 to 13 x 10(exp 11) cm(exp -2). For densities higher than about 6 x...
Dielectric function spectra of GaN, AlGaN, and GaN/AlGaN heterostructures (2001)
Wagner, J., Obloh, H., Kunzer, M., Maier, M., Köhler, K.
The pseudodielectric function spectra (epsilon) of wurtzite GaN, AlGaN, and GaN/AlGaN heterostructures were determined for photon energies ranging from 2 to 5 eV, using variable angle spectroscopic...
Field-induced delocalization and Zener breakdown in semiconductor superlattices (2001)
Rosam, B., Meinhold, D., Löser, F., Lyssenko, V., Leo, K., Glutsch, S., ...
We investigate the energy spectrum and the electron dynamics of a band in a semiconductor superlattice as a function of the electric field. Linear optical spectroscopy shows that, for high fields,...
Chapter 3: Bloch oscillations in semiconductors: Principles and applications (2001)
Sudzius, M., Lyssenko, V., Löser, F., Valusis, G., Hasche, T., Leo, K., ...
In this chapter we review recent studies of Bloch oscillations in semiconductor superlattices. Particular emphasis is put on interband optical experiments, where a coherent ensemble of carders is...
Field-Induced Delocalization and Zener Breakdown in Semiconductor Superlattices (2001)
Bechstedt, F., Glutsch, S., Köhler, K., Leo, K., Lyssenko, V. G., Löser, F., ...
Interaction of actinides with alumina-silica-colloids in statu nascendi. (2001)
Kim, M.A., Köhler, K., Panak, P., Klenze, R.
8th Internat.Conf.on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere (Migration '01), Bregenz, A, September 16-21, 2001
The functional unit of the renal type IIa Na+/Pi cotransporter is a monomer. (2000)
Köhler, K, Forster, I C, Lambert, G, Biber, J, Murer, H
The composition of the functional unit of the rat renal type IIa Na(+)/P(i) cotransporter (NaPi-IIa) was investigated by using two approaches based on the differential sensitivities of the wild type...
Lossy, R., Hilsenbeck, J., Würfl, J., Köhler, K., Obloh, H.
Processing technology for AlGaN/GaN HEMTs fabricated by 2-inch stepper lithography was developed. The performance of HEMTs is evaluated, showing a very good uniformity of electrical properties over...
Kundrotas, J., Valusis, G., Cesna, A., Kundrotaite, A., Dargys, A., Suziedelis A., ...
We present a detailed experimental study on photoluminescence quenching due to exciton and donor impact ionization by accelerated electrons under an in-plane nanosecond duration electric field...
Hülsmann, A., Benkhelifa, F., Bronner, W., Chertouk, M., Hurm, V., Köhler, K., ...
In this article we report on the status of metamorphic buffers and devices on GaAs grown by MBE. We compare metamorphic devices on GaAs with lattice matched devices on InP with respect to physical...
Complementary HFETs on GaAs with 0.2µm gate length (2000)
Leuther, A., Thiede, A., Köhler, K., Jakobus, T., Weimann, G.
A new technology for the integration of n- and p-hetero-FETs (HFETs) in complementary circuits on GaAs is presented. Our aim was to develop a complementary GaAs HFET technology using our existing...
Wagner, J., Ramakrishnan, A., Obloh, H., Kunzer, M., Köhler, K., Johs, B.
Spectroscopic ellipsometry (SE) has been used for the characterization of ALGaN/GaN and InGaN/GaN heterostructures. The resulting pseudodielectric function spectra were analyzed using a multilayer...
Self-Induced Shapiro effect in semiconductor superlattices (2000)
Löser, F., Dignam, M., Kosevich, Y., Köhler, K., Leo, K.
We observe that the oscillatory motion of photoinjected electron-hole pairs in a biased semiconductor superlattice (Bloch oscillation) is accompanied by a coherent quasi-dc current that is generated...
Reliability of InAlAs/InGaAs HEMTs grown on GaAs substrate with metamorphic buffer (2000)
Dammann, M., Chertouk, M., Jantz, W., Köhler, K., Weimann, G.
The long term stability of 0.25 mu m InAlAs/InGaAs HEMTs grown on GaAs substrate with metamorphic buffer (MM-HEMT) was investigated by biased accelerated life tests in air and in nitrogen. By...
Hole conductivity and compensation in epitaxial GaN:Mg layers (2000)
Kaufmann, U., Schlotter, P., Obloh, H., Köhler, K., Maier, M.
The concentration p and the mobility mu of holes in metal-organic chemical vapor deposition (MOCVD) GaN:Mg layers were studied by room temperature Hall-effect measurements as a function of the Mg...
Group III-Nitride heterostructures: From materials research to devices (2000)
Wagner, J., Obloh, H., Kunzer, M., Schlotter, P., Pletschen, W., Kiefer, R., ...
Group III-nitride based heterostructures are of rapidly growing importance for the fabrication of short-wavelength light-emitting devices as well as for high-power high-frequency field effect...
Wagner, J., Köhler, K., Ganser, P., Herres, N.
Interband transitions in GaAs, GaAs(1-x)N(x) (0
Leven, A., Hurm, V., Bronner, W., Köhler, K., Walcher, H., Kiefer, R., ...
A 40 GHz bandwidth, 1.55 mu m wavelength photoreceiver for high-speed digital and microwave-via-fiber applications is presented. The photoreceiver consists of a GaInAs/AlGaInAs/AlInAs multimode...
Photon drag investigations of current relaxation processes in a two-dimensional electron gas (2000)
Graf, S., Sigg, H., Köhler, K., Bächtold, W.
We have investigated the photon drag current that is excited by an infrared laser beam in the plane of the two-dimensional electron gas of GaAs/Al(0.35)Ga(0.65)As multiple-quantum-well systems. An...
Hawker, P., Kent, A., Challis, L., Bartels, A., Dekorsy, T., Kurz, H., ...
We have used pulse time-of-flight techniques to examine the phonon emission from an optically excited GaAs/AlAs superlattice structure. For laser excitation wavelengths shorter than 767 nm (the...
Hurm, V., Leven, A., Benz, W., Berking, M., Bronner, W., Hülsmann, A., ...
40 Gbit/s 1. 55 mu m photoreceivers were manufactured using GaAs-based HEMT distributed amplifiers. The photoreceivers include either a monolithic integrated surface-illuminated PIN photodiode or a...
Field-induced delocalization and zener breakdown in semiconductor superlattices (2000)
Rosam, B., Meinhold, D., Löser, F., Lyssenko, V., Leo, K., Glutsch, S., ...
We investigate the electronic structure in strongly coupled superlattices over a wide field range. It is shown that die Wannier-Stark localization is followed by a field-induced delocalization which...
Femtosecond pulse shaping for coherent carrier control (2000)
Heberle, A., Baumberg, J., Kuhn, T., Köhler, K.
We investigate coherent control of exciton dynamics in semiconductor quantum wells with Fourier-domain shaped pulses. Off-resonant optical nutation is demonstrated after excitation of quantum wells...
Coupled Bloch-phonon oscillations in semiconductor superlattices (2000)
Dekorsy, T., Bartels, A., Kurz, H., Köhler, K., Hey, R., Ploog, K.
We investigate coherent Bloch oscillations in GaAs/AlxGa(1-x)As superlattices with electronic miniband widths larger than the optical phonon energy. In these superlattices the Bloch frequency can be...
Optimization of InGaN/GaN quantum wells for violet GaN/InGaN/AlGaN LEDs (2000)
Ramakrishnan, A., Kunzer, M., Schlotter, P., Obloh, H., Pletschen, W., Köhler, K., ...
We report on the optimization of InGaN/GaN quantum wells (QWs) for use as the active region in violet GaN/InGaN/AlGaN LEDs. Strained In(0.13)Ga(0.87)N/GaN QWs were grown by metal-organic chemical...
Generation and manipulation of Bloch wave packets (2000)
Löser, F., Sudzius, M., Lyssenko, V., Kosevich, Y., Dignam, M., Köhler, K., ...
We show how the spatial dynamics of a Bloch oscillating wave packet can directly be measured and manipulated by means of optical techniques. For excitation below and above the Wannier-Stark ladder...
GaN static induction transistor fabrication (2000)
Weimann, G., Eastman, L.F., Obloh, H., Köhler, K.
We report on the design and development of a fully self-aligned manufacturing process for multifinger high-power GaN Static Induction Transistors, operating at X-band. A combined dry and wet etch...
Bauer, T., Hummel, A., Roskos, H., Köhler, K.
We present photocurrent spectra of the Wannier-Stark ladder of a GaAs/AlGaAs superlattice in a magnetic field up to 9 T and oriented along the growth direction of the superlattice. The Landau and...
Löser, F., Kosevich, Y., Köhler, K., Leo, K.
We investigate the influence of scattering and coherent plasmon coupling on the temporal and spatial dynamics of Bloch-oscillating electrons in a semiconductor superlattice. We demonstrate that the...
Direct Observation of dynamical screening of the intersubband resonance (2000)
Graf, S., Sigg, H., Köhler, K., Bächtold, W.
We have studied the intersubband resonance of GaAs, AlGaAs multi-quantum well systems by comparing photon drag and absorption spectra. The peak absorption at room temperature is found to be...
Direct observation of depolarization shift of the intersubband resonance (2000)
Graf, S., Sigg, H., Köhler, K., Bächtold, W.
We have studied the intersubband resonance of GaAs/AlGaAs multi-quantum-well systems by comparing photon drag and absorption spectra obtained by in-plane photocurrent and photoconduction...
Coupled Bloch-phonon oscillations in GaAs/AlGaAs superlattices: theory and experiment (2000)
Dekorsy, T., Bartels, A., Kurz, H., Ghosh, A., Jönsson, L., Wilkens, J., ...
We report on the femtosecond dynamics of coherent Bloch oscillations in GaAs/Al(x)Ga(l-x)As superlattices. In a superlattice with a miniband width equal to the optical phonon energy of GaAs the Bloch...
Ramakrishnan, A., Wagner, J., Kunzer, M., Obloh, H., Köhler, K.
In(0.13)Ga(0.87)N/GaN double heterostructures and quantum wells (QWs) have been studied by room-temperature photoluminescence (PL) and spectroscopic ellipsometry (SE). PL revealed the presence of...
Midbandgap electro-optic detection of Bloch oscillations (2000)
Först, M., Segschneider, G., Dekorsy, T., Kurz, H., Köhler, K.
Bloch oscillations excited in a biased GaAs/Al(x)Ga(1-x)As superlattice are investigated in a time-resolved two-color electro-optic detection scheme. The detection of resonantly excited Bloch...
Dammann, M., Chertouk, M., Jantz, W., Köhler, K., Marsetz, W., Schmidt, K., ...
By performing biased accelerated life tests and three dimensional temperature simulations the effect of drain voltage on reliability and channel temperature of pseudomorphic InAlAs/InGaAs HEMTs for...
Influence of fano coupling on Wannier-Stark transitions in semiconductor superlattices (2000)
Canzler, T.W., Holfeld, C.P., Lyssenko, V.G., Whittaker, D.M., Köhler, K., Leo, K.
Coupled Bloch-phonon oscillations in GaAs/AlGaAs superlattices: theory and experiment (2000)
T. Dekorsy, A. Bartels, H. Kurz, A.W. Ghosh, L. Jönsson, J.W. Wilkins, ...
We report on the femtosecond dynamics of coherent Bloch oscillations in GaAs=Al x Ga 1-x As superlattices. In a superlattice with a miniband width equal to the optical phonon energy of GaAs the Bloch...
Reduced threshold in pierced semiconductor microdisk lasers (1999)
Backes, S.A., Cleaver, J.R.A., Heberle, A.P., Baumberg, J.J., Köhler, K.
GaAs microdisk lasers with holes pierced through the disk surface are investigated for their threshold characteristics. Disks are fabricated with either a single hole or two diametrically opposite...
Nonharmonic Bloch Oscillations in GaAs/AlGaAs Superlattices (1999)
Litvinenko, K.L., Köhler, K., Leo, K., Löser, F., Lyssenko, V.
Influence of Electric Field on Photoluminescence Quenching in GaAs/AlGaAs Quantum Wells (1999)
Asmontas, S., Cesna, A., Gradauskas, J., Köhler, K., Kundrotaite, A., Kundrotas, J., ...
We present experimental study of the influence of an electric field applied inparallel to the layers of GaAs/Al(0.35)Ga(0.65)As quantum wells on the photoluminescence at liquid nitrogen temperature,...
New Features of Spatial-Temporal dynamics of Bloch Oscillations (1999)
Dignam, M., Köhler, K., Leo, K., Litvinenko, K.L., Löser, F., Lyssenko, V., ...
A short laser pulse exciting semiconductor superlattice induces quantum beats between different excitonic states that in turn lead to a formation of a time-varying coherent wave packet. A real...
Field-induced delocalization and zener breakdown in semiconductor superlattices (1999)
Rosam, B., Löser, F., Lyssenko, V., Leo, K., Glutsch, S., Bechstedt, F., ...
We investigate the electronic structure in strongly coupled superlattices over a wide field range. It is shown that the Wannier-Stark localization is followed by a field-induced delocalization which...
Dynamics of Bloch Oscillations: Influence of Excitation Conditions (1999)
Valusis, G., Lyssenko, V., Sudzius, M., Löser, F., Hasche, T., Leo, K., ...
The dynamics of the Bloch oscillations in GaAs/Al(0.3)Ga(0.7)As superlattices are studied experimentally applying spectrally-resolved four-wave mixing in a self-diffraction geometry. We have found...
High frequency optical rectification in bulk GaAs and asymmetric AlGaAs/GaAs quantum wells (1999)
Graf, S., Sigg, H., Köhler, K., Bächtold, W.
The mechanism of the huge optical rectification (OR) in asymmetrical quantum wells (AQW) has been investigated at high frequencies (HF) obtained by short far infrared pulses generated by a free...
Transport parameters of 2D systems derived from microwave transmission experiments (1999)
Brensing, A., Bauhofer, W., Köhler, K.
This paper reports on low temperature microwave transmission experiments which are performed in high magnetic fields on two-dimensional electron gas (2DEG) systems of heterostructure quantum wells....
Cyclotron mass of correlated two-dimensional electron GAS systems in GaAs (1999)
Manger, M., Batke, E., Köhler, K., Ganser, P.
The cyclotron mass of a high-density electron inversion layer in GaAs was investigated at a lattice temperature of 0.4 K. A novel mass minimum is observed in the metallic regime at a filling factor...
Threshold reduction in pierced microdisk lasers (1999)
Backes, S.A., Cleaver, J.R.A., Heberle, A.P., Baumberg, J.J., Köhler, K.
GaAs microdisk lasers with holes pierced through the disk surface are investigated for their threshold characteristics. Disks are fabricated with either a single hole or two diametrically opposite...
Gaymann, A., Maier, M., Köhler, K.
The redistribution of Be in highly doped Al(x)Ga(1-x)As layers and Al(x)Ga(1-x) As/AlAs(GaAs) short period superlattices (SPSL) during molecular beam epitaxy was investigated by secondary ion mass...
Reliability of passivated 0.15 mu m InAlAs/InGaAs HEMT's with pseudomorphic channel (1999)
Dammann, M., Chertouk, M., Jantz, W., Köhler, K., Schmidt, K.H., Weimann, G.
Accelerated life tests of 0. 15 mu m gate length InAlAs/InGaAs HEMTs were performed under DC electrical stress at four temperatures in nitrogen. By defining a 100 per cent-degradation of...
Chertouk, M., Dammann, M., Massler, M., Köhler, K., Weimann, G.
We report on fabrication, performance and reliability of 0. 15 mu m gate-length passivated InAlAs/InGaAs HEMTs with pseudomorphic channels. A 60 mu m gate width device had an ft of 160 GHz, and the...
Optical signal and energy transmission for a retina implant (1999)
Groß, M., Buß, R., Köhler, K., Schaub, J., Jäger, D.
In this paper we present the development of a signal and energy transmission technique for a retina implant This implant, called retina stimulator (RS), is part of a system designed to provide...
Millimeter-wave long-wavelength integrated optical receivers grown on GaAs (1999)
Baeyens, Y., Leven, A., Bronner, W., Hurm, V., Reuter, R., Köhler, K., ...
Compact monolithically integrated narrow-band photoreceivers with a high responsivity at millimeter-wave frequencies were realized. In these receivers, a 1.3-1.55 mu m wavelength In(0.53)Ga(0.47)As...
Milekhin, A.G., Rösch, M., Batke, E., Zahn, D.R.T., Köhler, K., Ganser, P., ...
The optical phonon modes in short-period GaAs/AlAs superlattices were investigated by means of Raman spectroscopy and far-infrared reflection spectroscopy using a grating coupler technique. Grating...
Grating-coupler excited interface phonos in GaAs/AlAs superlattices (1999)
Milekhin, A.G., Rösch, M., Batke, E., Köhler, K., Ganser, P.
The optical phonon modes of short-period GaAs/AlAs superlattices were investigated by means of far-infrared reflection spectroscopy using the grating coupler technique. Grating couplers provide a...
Coplanar W-band SPDT and SPtt resonated PIN diode switsches (1999)
Steinhagen, F., Massler, H., Haydl, W.H., Hülsmann, A., Köhler, K.
High performance single pole double throw (SPDT) and single pole triple throw (SPTT) switches optimized for center frequencies of 94 GHz and 77 GHz, were realized in coplanar waveguide GaAs MMIC...
Compositional dependence of the elastic constants and the lattice parameter of Al(x)Ga(1-x)As (1999)
Gehrsitz, S., Sigg, H., Herres, N., Bachem, K., Köhler, K., Reinhart, F.K.
Near infrared Brillouin scattering and high resolution x-ray diffraction is used for a precise determination of the elastic constants and the relaxed lattice parameters of Al(x)Ga(1-x)As epitaxial...
Bartels, A., Dekorsy, T., Kurz, H., Köhler, K.
Coherent zone-folded acoustic phonons are excited in GaAs/AlAs superlattices by femtosecond laser pulses via resonant impulsive stimulated Raman scattering in both forward and backward scattering...
Coherent acoustic phonons in GaAs/AlAs superlattices (1999)
Bartels, A., Dekorsy, T., Kurz, H., Köhler, K.
Coherent zone-folded acoustic phonons are generated in GaAs/AlAs superlattices by excitation with femtosecond laser pulses. Three modes of first and second backfolded order are driven by resonant...
Bloch oscillations in semiconductor superlattices (1999)
Lyssenko, V.G., Sudzius, M., Löser, F., Valusis, G., Hasche, T., Leo, K., ...
More than 60 years ago, Zener has predicted that an electron fit a periodic potential subject to a static electric field will perform harmonic oscillations (so-called Bloch oscillations) in real...
Köhler, K., Haungs, A., Leibrock, H., Rebel, H.
63.Physikertagung gemeinsam mit der Frühjahrstagung DPG, Heidelberg, 15.-19. März 1999
Direct observation of the rotational direction of electron spin precession in semiconductors. (1998)
Oestreich, M., Hägele, D., Schneider, H. C., Knorr, A., Hansch, A., Hallstein, S., ...
Sudzius, M., Lyssenko, V., Valusis, G., Löser, F., Hasche, T., Dignam, M., ...
We present a novel experimental technique which allows to precisely measure the spatial displacement of Blochoscillating electrons in semiconductor superlattices as a function of time: The dipole...
Litvinenko, K.L., Okhrimenko, I., Köhler, K., Lyssenko, V., Leo, K., Löser, F.
The variation of the spectral -shape of the four-wave mixing signal in GaAs/AlGaAs superlattices was studied experimentally and theoretically. It was shown that in an external electric field, leading...
Chertouk, M., Steinhagen, F., Massler, H., Dammann, M., Haydl, W.H., Köhler, K., ...
InP-based HEMTs have to date demonstrated the best high frequency characteristics of any transistor, including the highest f(t) and f(max), the lowest noise figure and the highest efficiencies for...
Gaymann, A., Maier, M., Köhler, K., Bronner, W., Grotjahn, F., Hornung, J., ...
Detailed studies of segregation and diffusion of the dopants Si and Be in MBE grown AlGaAs/GaAs heterostructures for optoelectronic devices are presented. Segregation of Si could be suppressed by...
Polariton motional narrowing in semiconductor multiple quantum wells (1998)
Baumberg, J.J., Heberle, A.P., Kavokin, A.V., Vladimirova, M.R., Köhler, K.
We demonstrate a new fast-scan ultrafast coherent reflectivity technique that tracks the amplitude and phase of excitons in GaAs heterostructures at densities down to 4 X 10(exp 6) cm(-2). Observed...
Chertouk, M., Steinhagen, F., Massler, H., Haydl, W.H., Köhler, K., Weimann, G.
A 0.15 mu m high gain, passivated, double-side-doped InAlAs/ InGaAs HEMT with high uniformity over 2in InP substrates has been developed. A measured gain of 12.5dB at 94GHz was achieved at a drain...
Sudzius, M., Lyssenko, V.G., Löser, F., Leo, K., Dignam, M.M., Köhler, K.
We use a technique to measure the spatial dynamics of Bloch wave packets in semiconductor superlattices and investigate the dependence of the dynamics on the optical excitation conditions. For...
A NLTL-based integrated circuit for a 70-200 GHz VNA system (1998)
Wohlgemuth, O., Agarwal, B., Pullela, R., Mensa, D., Lee, Q., Guthrie, J., ...
We present an integrated circuit, based on nonlinear transmission lines (NLTL), for network analysis within 70-200 GHz. This is the first integrated circuit containing all elements of a S-Parameter...
Bronner, W., Benz, W., Dammann, M., Ganser, P., Grün, N., Hurm, V., ...
A monolithic integrated optoelectronic receiver for a wavelength of 1.55 mu m consisting of a GaInAs PIN diode and a transimpedance AlGaAs/GaAs HEMT amplifier has been fabricated. The available...
Modulator driver and photoreceiver for 20 Gb/s optic-fiber links (1998)
Lao, Z., Hurm, V., Thiede, A., Berroth, M., Ludwig, M., Lienhart, H., ...
Two integrated circuits, a modulator driver and a photoreceiver integrating a metal-semiconductor-metal (MSM) photodetector, a differential transimpedance amplifier and two limiting amplifier stages...
Mixed signal integrated circuits based on GaAs HEMTs (1998)
Thiede, A., Schlechtweg, M., Lang, M., Leber, P., Lao, Z., ...
During the past five years numerous mixed signal integrated circuits (IC's) have been designed, processed, and characterized based on our 0.2 mu m gate length AlGaAs/GaAs quantum well HEMT...
Millimeter wave InP HEMT MMIC technology. Thermal stability and performace (1998)
Chertouk, M., Steinhagen, F., Massler, H., Dammann, M., Haydl, W.H., Köhler, K., ...
InP-based HEMTs have to date demonstrated the best high frequency characteristics of any transistor, including the highest f(t) and f(max), the lowest noise figure and the highest efficiencies for...
Microdisk laser structures for mode control and directional emission (1998)
Backes, S.A., Cleaver, J.R.A., Heberle, A.P., Köhler, K.
GaAs microdisk laser structures with modified resonator geometry have been investigated. Device fabrication employs electron-beam lithography and etch procedures for generating disks with notches,...
Thiede, A., Lao, Z., Lienhart, H., Sedler, M., Seibel, J., Hornung, J., ...
A 16 x 16 bit parallel multiplier based on a 26 k sea-of-gate has been fabricated successfully to demonstrate the LSI capability of our mixed signal IC technology including pseudomorphic T-gate HEMTs...
Hu, C.M., Batke, E., Köhler, K., Ganser, P.
Cyclotron resonance of inversion layer electrons in GaAs was studied from liquid helium temperatures up to 110 K for densities smaller than 10(exp11)cm(-2) . A continuous red shift of the resonance...
Leven, A., Baeyens, Y., Benz, W., Bronner, W., Hülsmann, A., Hurm, V., ...
Pin-photodiodes for a wavelength of 1.55 mu m were monolithically integrated on GaAs with 0.15 mu m gate-length pseudomorphic HEMTs using a linear graded metamorphic InGaAlAs buffer. We designed and...
Fano resonances in semiconductor superlattices (1998)
Holfeld, C.P., Löser, F., Sudzius, M., Leo, K., Whittaker, D.M., Köhler, K.
We report the first observation of Fano resonances in biased semiconductor superlattices: The excitonic Wannier-Stark ladder transitions show asymmetric absorption due to the coupling to the continua...
Effect of atmosphere on reliability of passivated 0.15 mu m InAlAs/InGaAs HEMTs (1998)
Dammann, M., Chertouk, M., Jantz, W., Köhler, K., Schmidt, K.H., Weimann, G.
The influence of ambient atmosphere on the long term stability of InP-based HEMTs has been investigated. By performing accelerated stress tests at elevated temperature the authors found that the...
Direct observation of the rotational direction of electron spin precession in semiconductors (1998)
Oestreich, M., Hägele, D., Schneider, H.C., Knorr, A., Hansch, A., Hallstein, S., ...
A new experimental method is presented to determine the sign of the electron Land' g factor in semiconductors by time-resolved magneto photoluminescence. This technique is used to demonstrate the...
Coupled cyclotron resonance transitions of bilayer 2DEG systems in GaAs (1998)
Hu, C.M., Batke, E., Shen, S.C., Köhler, K., Ganser, P.
Electron cyclotron resonances in bilayer quasi two-dimensional electron systems are examined in the extreme magnetic quantum limit. The variation of the resonance frequencies with electron density...
Coherent dynamics of continuum and excitonic states in quantum confined systems (1998)
Bakker, H.J., Dekorsy, T., Cho, G.C., Kurz, H., Leisching, P., Köhler, K.
We present an experimental study on the coherent dynamics of charge carriers in semiconductor heterostructures, i.e. Bloch oscillations in superlattices and intervalence band quantum beats in single...
Coherent control of acoustic phonons in semiconductor superlattices (1998)
Bartels, A., Dekorsy, T., Kurz, H., Köhler, K.
Coherent acoustic phonons are generated in GaAs/AlAs superlattices by excitation with femtosecond laser pulses. Several modes of the acoustic phonon spectrum are observed, in agreement with the...
Bloch wave packets in semiconductor superlattices: Composition and spatial displacement (1998)
Löser, F., Sudzius, M., Lyssenko, V.G., Hasche, T., Leo, K., Dignam, M.M., ...
We investigate the temporal and spatial displacement dynamics of optically excited wave packets in a semiconductor superlattice. We present an experimental technique which measures directly the...
40 Gbit/s 1.55 mu m pin-HEMT photoreceiver monolithically integrated on 3in GaAs substrate (1998)
Hurm, V., Benz, W., Bronner, W., Hülsmann, A., Jakobus, T., Köhler, K., ...
A 36.5GHz bandwidth, 1.55 mu m wavelength pin-HEMT photoreceiver with a distributed amplifier has been monolithically integrated on a 3in GaAs substrate using a 0.15 mu m gate-length pseudomorphic...
40 Gbit/s 1.55 mu m monolithic integrated GaAs-based PIN-HEMT photoreceiver (1998)
Hurm, V., Benz, W., Bronner, W., Hülsmann, A., Jakobus, T., Köhler, K., ...
A 36.5 GHz bandwidth 1.55mu m wavelength PIN-HEMT photoreceiver with a distributed amplifier has been monolithically integrated on a 3-inch GaAs substrate. The PIN photodiode has a responsivity of...
40 Gb/s high-power modulator driver IC for lightwave communication systems (1998)
Lao, Z., Thiede, A., Nowotny, U., Lienhart, H., Hurm, V., Schlechtweg, M., ...
A monolithic integrated modulator driver with a data decision function for high-speed optical fiber links is presented. The integrated circuit (IC) was manufactured in a 0.2- mu m gate length...
20-Gb/s 14-k ohm transimpedance long-wavelength MSM-HEMT photoreceiver OEIC (1998)
Lao, Z., Hurm, V., Bronner, W., Hülsmann, A., Jakobus, T., Köhler, K., ...
A fully monolithically integrated photoreceiver composed of a metal-semiconductor-metal (MSM) photodetector, a transimpedance amplifier and three limiting amplifier stages for high-speed...
Ultrafast coherent carrier control in quantum wells (1997)
Baumberg, J.J., Heberle, A.P., Köhler, K., Kavokin, A.V.
A fast scanning ultrafast phase-dependent reflectivity technique is used to measure the coherent properties of multiple quantum wells at carrier densities below 108 cm (exp -2). Signal to noise...
Ultrafast acoustic phonon ballistics in semiconductor heterostructures (1997)
Baumberg, J.J., Williams, D.A., Köhler, K.
Using a two-color ultrafast surface deflection spectroscopy, we demonstrate the time-resolved observation of acoustic phonon wave packets emitted from a single buried GaAs quantum well. A...
Spin flip of excitons in GaAs quantum wells (1997)
Snoke, D.W., Rühle, W.W., Köhler, K., Ploog, K.
We report measurements of the rates of conversion from J = 2 excitons to J = 1 excitons, as well as conversion from right-handed J = 1 excitons to left-handed J = 1 excitons, and measurement of the...
Shape dependence of emission from microdisk lasers (1997)
Backes, S.A., Heberle, A.P., Cleaver, J.R.A., Köhler, K.
The emission characteristics of GaAs Whispering Gallery microdisk lasers have been investigated for different disk shapes and sizes. Elliptical structures showed a substantial increase in the...
Optically pumped, indirect-gap Al(x)Ga(1-x)As lasers (1997)
Wörner, A., Westphäling, R., Kalt, H., Köhler, K.
We demonstrate optically pumped lasers with active layers of indirect-gap Al(x)Ga(1-x)As operating up to room temperature. The emission wavelength is 609 nm at 20 K and 639 nm at 300 K, respectively....
Gaymann, A., Schaub, J., Bronner, W., Grün, N., Hornung, J., Köhler, K.
Vertically compact Al(x)Gal(1-x)As/GaAs laser structures with Al(0.3)Ga(0.7)As/AlAs SPSL-cladding layers were grown top of HEMT structures by MBE and investigated with regard to series resistance. We...
Haupt, M., Köhler, K., Ganser, P., Müller, S., Rothemund, W.
Ternary Al(x)In(1-x)As/Ga(y)In(1-y)As heterostructures with a lattice mismatch up to 4 per cent are grown on GaAs by molecular beam epitaxy. Two buffer layer concepts to compensate the lattice misfit...
Thiede, A., Schlechtweg, M., Hurm, V., Lang, M., Leber, P., ...
During the past 5 years numerous mixed signal circuits have been designed, processed, and characterized based on our 0.2 mu m gate length AlGaAs/GaAs/AlGaAs E/D quantum well HEMT technology....
Long wavelength MSM-HEMT and PIN-HEMT photoreceivers grown on GaAs (1997)
Hurm, V., Benz, W., Bronner, W., Fink, T., Jakobus, T., Kaufel, G., ...
1.3-1.55 mu m wavelength 20 Gbit/s MSM-HEMT and 10 Gbit/s PIN-HEMT photoreceivers have been monolithically integrated on GaAs substrates using a 0.3 mu m gate length AlGaAs/GaAs HEMT process. The...
Influence of LO-phonon emission on bloch oscillations in semiconductor superlattices (1997)
Wolter, F., Roskos, H.G., Haring Bolivar, P., Bartels, G., Kurz, H., Köhler, K., ...
The intraband phase coherence of electronic Bloch wavepackets in semiconductor superlattices is partially conserved when electrons undergo energy relaxation by LO-phonon emission. The decay time of...
High-speed long-wavelength monolithic integrated photoreceivers grown on GaAs (1997)
Hurm, V., Benz, W., Bronner, W., Fink, T., Köhler, K., Lao, Z., ...
The first 20 Gbit/s 1.3-1.55 mu m wavelength monolithic integrated photoreceiver grown on GaAs substrate has been fabricated using a 0.3 mu m gate length AlGaAs/GaAs HEMT process. At a wavelength of...
High power modulator driver ICs up to 30 Gb/s with AlGaAs/GaAs HEMTs (1997)
Lao, Z., Thiede, A., Nowotny, U., Schlechtweg, M., Hurm, V., Bronner, W., ...
Two monolithic integrated transmitter circuits of a modulator driver and a modulator driver with a 2:1 multiplexer for high-speed optical-fiber links are presented. The ICs featuring differential...
Marsetz, W., Hülsmann, A., Kleindienst, T., Fischer, S., Demmler, M., Bronner, W., ...
Double recessed T-gate Al(0.2)Ga(0.8)Aa/In(0.25)Ga(0.75)As pseudomorphic HEMTs with 0.3 mu m gate length and different upper recess widths have been processed and analyzed. Systematic investigations...
HEMT circuits for signal/data processing (1997)
Berroth, M., Hurm, V., Lang, M., Lao, Z., Thiede, A., ...
HEMT devices exhibit excellent figures of merit for high frequency operation. Therefore they are strong candidates for high speed signal and data processing. This article presents an overview of...
GaAs HEMT ICs for 40 Gbit/s data transmission systems (1997)
Lang, M., Nowotny, U., Lao, Z., Thiede, A., Rieger-Motzer, M., ...
Using our 0.2 mu m AlGaAs/GaAs/AlGaAs quantum well HEMT technology, we have designed, manufactured and characterized different ICs for optoelectronic data transmission systems. In this paper we...
Haring Bolivar, P., Wolter, F., Müller, A., Roskos, H.G., Kurz, H., Köhler, K.
THz-emission experiments are presented which demonstrate a limitation of the semiconductor Bloch equations (SBE) for the description of the Coulomb interaction in semiconductors optically excited...
Alphenaar, B.W., Baumberg, J.J., Köhler, K.
We create a reservoir of hole traps in a resonant tunneling light emitting diode by etching the p-type contact into an array of nanometer scale pillars. In the off state, the charge reservoir keeps...
Lyssenko, V.G., Sudzius, M., Valusis, G., Löser, F., Hasche, T., Leo, K., ...
Bloch oscillations in semiconductor superlattices have recently been observed using optical techniques. However, it remained to show that the optically observed quantum beats of the Wannier-Stark...
Lyssenko, V.G., Valusis, G., Löser, F., Hasche, T., Leo, K., Köhler, K., ...
The absolute spatial displacement of Bloch-oscillating electrons in semiconductor superlattices is measured as a function of time with a few angstrom resolution using a novel experimental technique:...
Coulomb-renormalized intraband dynamics probed by THz emission (1997)
Wolter, F., Haring Bolivar, P., Bartels, G., Roskos, H.G., Kurz, H., Axt, V.M., ...
THz emission from a narrow-miniband superlattice excited at its lower band edge reveals a hyperbolic bias dependence of the emission frequency. This reflects the emission from Coulomb-renormalized...
Fink, T., Haupt, M., Kaufel, G., Köhler, K., Braunstein, J., Massler, H.
Ternary Al(0.48)In(0.52) As/Ga(0.47)In(0.53)As/Al(0.48)In(0.52)As MODFET structures on top of a buffer on GaAs substrate have been grown by molecular beam epitaxy. For a smooth transition between the...
Bartels, G., Cho, G.C., Dekorsy, T., Kurz, H., Stahl, A., Köhler, K.
Transient pump-probe signals of a GaAs/Al(x)Ga(1-x)As quantum well are investigated both theoretically and experimentally for different excitation conditions. The calculations are based on a...
Gaymann, A., Maier, M., Bronner, W., Grün, N., Köhler, K.
Dopant diffusion is investigated by depth profiling with secondary ion mass spectrometry (SIMS) in heterostructures containing Be-doped short-period superlattice Al(x)Ga(1-x)As layers (0.3 =< x =<...
40 GHz monolithically-integrated fully-balanced VCO using 0.3 mu m HEMTs (1997)
Berroth, M., Thiede, A., Rieger-Motzer, M., Jakobus, T., Hülsmann, A., ...
A monolithically-integrated, fully balanced VCO with a central frequency of about 40GHz has been designed and realised using capacitively-coupled HEMT-triples as active components, on-chip coplanar...
Lao, Z., Berroth, M., Hurm, V., Thiede, A., Bosch, R., Hofmann, P., ...
Automatic-gain-control (AGC), transimpedance, and limiting amplifiers are key elements in optical-fiber links and measuring equipment. An AGC amplifier operating up to 13Gb/s, a transimpedance...
20 Gbit/s long wavelength monolithic integrated photoreceiver grown on GaAs (1997)
Hurm, V., Benz, W., Bronner, W., Fink, T., Kaufel, G., Köhler, K., ...
The first 20Gbit/s 1.3-1.55mu m wavelength monolithic integrated photoreceiver grown on GaAs substrate has been fabricated using AlGaAs/GaAs HEMTs. At a wavelength of 1.3mu m, the integrated InGaAs...
20-40 Gb/s 0.2-mu m GaAs HEMT chip set for optical data receiver (1997)
Lang, M., Lao, Z., Schlechtweg, M., Thiede, A., Rieger-Motzer, M., ...
Using our 0.2-mu m AlGaAs/GaAs/AlGaAs quantum well high electron mobility transfer (HEMT) technology, we have developed a chip set for 20-40 Gb/s fiber-optical digital transmission systems. In this...
10 Gbit/s long wavelength pin-HEMT photoreceiver grown on GaAs (1997)
Hurm, V., Benz, W., Bronner, W., Dammann, M., Jakobus, T., Kaufel, G., ...
The first long wavelength pin-HEMT photoreceiver grown on GaAs has been manufactured using a 0.3mu m gate length AlGaAs/ GaAs HEMT process. At a wavelength of 1.55mu m the monolithically integrated...
W-band MMIC VCO with a large tuning range using a pseudomorphic HFET (1996)
Bangert, A., Schlechtweg, M., Lang, M., Haydl, W., Bronner, W., Fink, T., ...
A widely tunable oscillator with a center frequency of 94 GHz including a two stage buffer amplifier has been designed and fabricated. The output power was 6 mW. The mechanical tuning range by...
Ultrafast photon drag detector for intersubband spectroscopy (1996)
Sigg, H., Graf, S., Kwakernaak, M.H., Margotte, B., Erni, D., Van Son, P., ...
The Photon drag effect of a 2D electron gas is measuring the ps infrared pulses of the wavelength-tunable free electron laser source FELIX. The pulsed photon drag rseponse is found to depend...
Ultrafast hole-lattice thermalization in GaAs quantum wells (1996)
Hunsche, S., Kim, A.M.T., Dekorsy, T., Kurz, H., Köhler, K.
We study the thermalisation of optically excited cold holes in GaAs quantum wells using time-resolved femtosecond pump-probe measurements. After optical excitation at the lowest heavy-hole...
Ultrafast coherent carrier control in quantum wells (1996)
Heberle, A.P., Baumberg, J.J., Köhler, K., Ploog, K.
We demonstrate femtosecond coherent control of excitons in quantum wells with phase-locked pairs of 100 fs infrared pulses. Co-polarised pulses allow control of exciton density and coherent...
Ultrafast coherent carrier control in quantum wells (1996)
Baumberg, J.J., Heberle, A.P., Köhler, K., Ploog, K.
We report the coherent control of excitons in quantum wells with pairs of 150-fs infrared pulses. Oscillations in the exciton density versus inter-pump-pulse separation, which correspond to the...
Time-resolved study of intervalence band thermalization in a GaAs quantum well (1996)
Kim, A.M.T., Hunsche, S., Dekorsy, T., Kurz, H., Köhler, K.
The thermalization of optically excited cold holes in a GaAs quantum well is investigated by femtosecond two-color pump-probe measurements. Clear evidence is found for scattering from heavy-holes...
Time-resolved optical investigations of Bloch oscillations in semiconductor superlattices (1996)
Dekorsy, T., Ott, R., Leisching, P., Bakker, H.J., Waschke, C., Roskos, H.G., ...
We present a complementary study of the interband and intraband dynamics of optically excited Bloch oscillations in GaAs/Al(ind x)Ga(ind 1-x)As superlattices. Distinct differences in the frequency...
Resonant polaron coupling of high index electron Landau levels in GaAs heterostructures (1996)
Hu, C.M., Batke, E., Köhler, K., Ganser, P.
The resonant polaron coupling of high index Landau levels was investigated for quasi-two-dimensional electron inversion layers in GaAs. Strong polaron mass enhancements were observed in magnetic...
Relaxation dynamics of electrons between Landau levels in GaAs (1996)
Hannak, R.M., Rühle, W.W., Köhler, K.
The relaxation dynamics of free electrons between Landau levels is traced on a picosecond time scale via the time evolution of the band-to-acceptor luminescence in p-type GaAs after resonant...
Quantum coherence of continuum states in the valence band of GaAs quantum wells (1996)
Dekorsy, T., Kim, A.M.T., Cho, G.C., Hunsche, S., Bakker, H.J., Kurz, H., ...
Quantum beats of heavy and light holes in GaAs quantum wells are investigated in femtosecond time-resolved four-wave mixing and transmission experiments as a function of optical excitation energy....
Photon drag spectroscopy of a two-dimensional electron system (1996)
Sigg, H., Son, P. Van, Köhler, K.
The photon drag effect in a two-dimensional electron gas of a GaAs/AlGaAs multi-quantum well system is measured using the ps infrared pulses of the wavelength-tunable free electron laser source...
Optical study of Bloch oscillations in superlattices (1996)
Cho, G.C., Dekorsy, T., Bakker, H.J., Kohl, A., Opitz, B., Köhler, K., ...
We present a comparative study of Bloch oscillations in InGaAsP/InGaAsP and GaAs/AlGaAs superlattices by different optical techniques. The visibility of Bloch oscillations in InGaAsP/InGaAsP is...
Nonlinear optical studies of Bloch oscillations (1996)
Leisching, P., Beck, W., Kurz, H., Köhler, K., Schäfer, W., Leo, K.
We have investigated the coherent dynamics of wave packets in semiconductor superlattices with an applied electric field. In particular, we have performed four-wave mixing experiments with...
The growth of heterostructures for opto-electronic devices by molecular beam epitaxy is described. As this first of approximately one hundred process steps determines the threshold voltages of...
Wisniewski, P., Suski, T., Litwin-Staszewska, E., Brunthaler, G., Köhler, K.
We demonstrate that different spatial correlations among remote impurity charges in the GaAs/AlGaAs quantum well lead to different values of (i) the transport-relaxation time, (ii) the...
Metal-non-metal transition at the crossover from antidots to quantum dots (1996)
Lütjering, G., Weiss, D., Tank, R.W., Klitzing, K. Von, Hülsmann, A., Jakobus, T., ...
A three-dimensionally structured gate resembling a pillared hall allows the exertion of a strong potential modulation on a two- dimensional electron gas in a GaAs AlGaAs heterostructure. The system...
Low power data decision IC for 20-40 Gbit/s data links using 0.2 mu m AlGaAs/GaAs HEMTs (1996)
Berroth, M., Thiede, A., Rieger-Motzer, M., Hofmann, P., Hülsmann, A., ...
A decision IC for optical data links at bit rates of 20-40 Gbit/s has been realised by using 0.2mu m AlGaAs/GaAs HEMT technology and tested on-wafer at bit rates up to 25 Gbit/s. The IC can be...
Intersubband plasmon-phonon modes of a quasi two-dimensional electron gas in GaAs (1996)
Friedrich, T., Rösch, M., Latussek, V., Batke, E., Köhler, K., Ganser, P.
The coupling of longitudinal-optical bulk phonons to grating induced intersubband resonances was investigated for electrons in a GaAs quantum well by far-infrared transmission and reflection...
Hu, C.M., Batke, E., Köhler, K., Ganser, P.
The resonant polaron effect was investigated for cyclotron transitions N-> N + 1 in magnetic field regimes where the Landau levels N = 2 and 3 cross with the level N = 0 plus one bulk longitudinal...
Brunthaler, G., Penn, C., Suski, T., Wisniewski, P., Litwin-Staszewska, E., Köhler, K.
Silicon modulation delta -doped GaAs/AlGaAs quantum wells were investigated by Hall effect and Shubnikov de Haas measurements. The two-dimensional carrier concentration ns was either changed with...
Haupt, M., Köhler, K., Ganser, P., Emminger, S., Müller, S., Rothemund, W.
Morphological and physical properties of Al0.48In0.52As/Ga0.47In0.53As heterostructures grown by molecular beam epitaxy, lattice relaxed on GaAs substrates and lattice matched on InP substrates, are...
Haupt, M., Ganser, P., Köhler, K., Emminger, S., Müller, S., Rothemund, W.
Ternary Al0.48In0.52As/Ga0.47In0.53As heterostructures lattice matched to InP offer a wide range of applications for electronic and opto-electronic devices. This material system is especially...
Field enhanced blockade of the confined energy levels in nanometer scale pillar arrays (1996)
Alphenaar, B.W., Durrani, Z.A.K., Wagner, M., Köhler, K.
We report observations of dramatic hysteretic switching behavior in nanometer scale pillar arrays. Using a new technique, we fabricate arrays of closely packed pillars 20-50 nm in diameter from a...
Schäfer, W., Shah, J., Damen, T.C., Cunningham, J.E., Goossen, K.W., ...
We present a unified microscopic approach to four-wave mixing (FWM) in semiconductors on an ultrashort time scale. The theory is valid for resonant excitation in the vicinity of the excitonic...
Exciton dephasing in quantum wells. Influence of spectral fluctuation processes (1996)
Löser, F., Neuber, A., Klatt, D., Lyssenko, V.G., Leo, K., ...
We perform spectrally resolved three-beam four-wave-mixing experiments in GaAs/AlGaAs quantum wells. The various resonances in these structures show very different decay parameters as a function of...
Dissipative tunneling in asymmetric double-quantum-well system. A coherence phenomenon (1996)
Vaupel, H., Thomas, P., Kühn, O., May, V., Maschke, K., Heberle, A.P., ...
Recent experiments on asymmetric double-quantum-well systems revealed unexpected long time scales of resonant tunnel processes as well as deviations from the expected dependence of the tunneling...
Dephasing dynamics of wave packets in semiconductor superlattices (1996)
Valusis, G., Lyssenko, V.G., Klatt, D., Löser, F., Leo, K., ...
We investigate the dephasing dynamics of Bloch oscillations in semiconductor superlattices by transient spectrally resolved four-wave mixing. The dephasing phenomena are studied under various carrier...
Dephasing and selection rules of interband and intraband polarisations in superlattices (1996)
Leisching, P., Dekorsy, T., Bakker, H.J., Roskos, H.G., Kurz, H., Köhler, K.
We study the coherent dynamics of interband and intraband polarizations of Bloch oscillations in a GaAs/ Al(0.7)Ga(0,3)As semiconductor superlattice. Time-resolved measurements of both polarizations...
Critical point broadening in the dielectric function of thin AlAs barriers on GaAs (1996)
Wagner, J., Weimar, U., Gaymann, A., Köhler, K.
Single AlAs barriers embedded in GaAs were studied by spectroscopic ellipsometry and Raman spectroscopy. For AlAs barrier widths below 10 nm the E1 and El + Delta 1 critical point resonances in the...
Coplanar millimeter-wave IC's for W-band applications using 0.15 mu m pseudomorphic MODFETs (1996)
Schlechtweg, M., Haydl, W.H., Bangert, A., Braunstein, J., Tasker, P.J., Verweyen, L., ...
A small signal S-parameter and noise model for the cascode MODFET has been validated up to 120 GHz, allowing predictable monolithic microwave integrated circuit (MMIC) design up to W-band. The...
Müller, S., Weyer, J.L., Köhler, K., Jantz, W., Frigeri, C.
The vertical structure of AlGaAs/GaAs epitaxial layer systems for micro- and optoelectronic device fabrication has been studied by selective etching combined with AFM imaging. Dark etching and...
Coherent exciton dynamics as a function of quantum-well number (1996)
Weber, D., Feldmann, J., Göbel, E.O., Stroucken, T., Knorr, A., Koch, S.W., ...
We have investigated the coherent dynamics of excitons in a single, a double, and a quintuple quantum-well structure under resonant excitation. In pump and probe experiments on the quintuple quantum...
Berroth, M., Thiede, A., Rieger-Motzer, M., Hofmann, P., Hülsmann, A., ...
SDH/SONET optical networks have so far been standardized for data rates up to 10 Gb/s (9.95328 Gb/s) in the synchronous transfer module level STM-64/STS192. The next higher level may possibly be a...
Broadening of interband resonances in thin AlAs barriers embedded in GaAs (1996)
Weimar, U., Wagner, J., Gaymann, A., Köhler, K.
AlAs barriers embedded in GaAs were studied by spectroscopic ellipsometry and resonant Raman scattering. Heterostructures with AlAs barrier widths ranging from 2 to 30 nm were grown by molecular-beam...
Bloch oscillations of excitonic and continuum states in superlattices (1996)
Leisching, P., Dekorsy, T., Bakker, H.J., Roskos, H.G., Köhler, K., Kurz, H.
Bloch oscillations. Coherent control of wave packet dynamics in superlattices (1996)
Lyssenko, V.G., Valusis, G., Löser, F., Hasche, T., Leo, K., Köhler, K., ...
Bloch oscillations in semiconductor superlattices have recently been observed using optical techniques. The main point which makes these quantum beats of the Wannier-Stark ladder to Bloch...
Fink, T., Haupt, M., Köhler, K., Raynor, B., Braunstein, J., Massler, H., ...
Employing molecular beam epitaxy, we have grown identical Al(0.48)In(0.52)As/Ga(0.47)In(0.53)As/Al(0.48)In(0.52)As MODFET structures lattice matched to InP substrates asl as on GaAs substrates using...
Berroth, M., Thiede, A., Rieger-Motzer, M., Hofmann, P., Hülsmann, A., ...
A 40 and 20 Gbit/s clock recovery IC has been realised by using a fully-balanced narrowband regenerative frequency divider with 0,2 mu m AlGaAs/GaAs HEMTs. The recovered clock signal has a time...
20 Gbit/s fully integrated MSM-photodiode AlGaAs/GaAs-HEMT optoelectronic receiver (1996)
Hurm, V., Benz, W., Berroth, M., Bronner, W., Kaufel, G., Köhler, K., ...
A 0.85 mu m wavelength monolithic integrated optoelectronic receiver consisting of a GaAs MSM photodiode and a multi-stage AlGaAs-GaAs HEMT amplifier has been fabricated. The transimpedance is 12.6 k...
20-40 Gbit/s 0.2 mu m GaAs HEMT chip set for optical data receiver (1996)
Berroth, M., Lang, M., Lao, Z., Thiede, A., Rieger-Motzer, M., ...
Using our 0.2 mu m AlGaAs/GaAs/AlGaAs quantum well HEMT technology, we have designed a chip set for 20-40 Gbit/s transmission systems. In this paper we describe five chips for the receiver side. The...
10 Gbit/s long-wavelength monolithic integrated optoelectronic receeiver grown on GaAs (1996)
Hurm, V., Benz, W., Berroth, M., Bronner, W., Fink, T., Haupt, M., ...
The first 10 Gbit/s long-wavelength monolithic integrated photoreceiver grown on GaAs substrate has been fabricated using a 0.3 mu m gate length AlGaAs/GaAs HEMT process. At a wavelength of 1.3 mu m...
10 and 20 Gbit/s clock recovery GaAs IC with 288 deg phase-shifting function (1996)
Berroth, M., Thiede, A., Rieger-Motzer, M., Hofmann, P., Hülsmann, A., ...
A 10 and 20Gbit/s clock recovery IC with 180 deg switched and 288 deg continuously variable phase-shifting function has been realised using 0.2/0.3mu m HEMT technology. The recovered clock signal has...
X(5) signature in th four-wave-mixing signal from a GaAs/Al(0.3)Ga(0.7)As superlattice (1995)
Bartels, G., Axt, V.M., Victor, K., Stahl, A., Leisching, P., Köhler, K.
We analyze coherent beats with a period corresponding to the biexciton binding energy in time-integrated four-wave-mixing experiments in a GaAs/Al0.3Ga0.7As superlattice at high excitation densities....
Sigg, H., Kwakernaak, M.H., Margotte, A.B., Erni, D., Van Son, P., Köhler, K.
A novel room temperature GaAs/AlGaAs multiquantum-well photon drag detector operating in the 10 mu m wavelength range and designed as a microstrip transmission line has been developed....
Ultrafast coherent control and destruction of excitons in quantum wells (1995)
Heberle, A.P., Baumberg, J.J., Köhler, K.
We demonstrate the coherent destruction of photogenerated excitons in semiconductor quantum wells within a few hundred ferntoseconds of their excitation. Coherent control of carrier dynamics is...
Time-resolved luminescence of semiconductor heterostructures in high magnetic field (1995)
Heberle, A.P., Haacke, S., Oestreich, M., Potemski, M., Rühle, W.W., Maan, J.C., ...
Kuball, M., Kelly, M.K., Santos, P.V., Cardona, M., Köhler, K., Wagner, J.
We report on ellipeometrie measurements of the doping dependence of the E1 and 1+ Delta1 critical points in highly doped n-type GaAs(100) exposed to air (up to doping concentrations of...
Spin-split cyclotron resonance and spatial distribution of interacting electrons (1995)
Hu, C.M., Friedrich, T., Batke, E., Köhler, K., Ganser, P.
The interaction coupling of cyclotron transitions with different spin orientation was investigated as a function of density for electron inversion layers in GaAs in the magnetic quantum limit. The...
Resonance fluorescence and polariton effects in GaAs thin layers (1995)
We have analyzed the photoluminescence (PL) of thin bulklike GaAs layers under nearly resonant excitation by transform-limited picosecond laser pulses. The PL spectra show clear signatures of...
Löser, F., Klatt, D., Leo, K., Bakker, H., Shah, J., ...
The polarization and population dynamics of resonantly generated excitions in GaAs/AlGaAs quantum well structures are investigated using transient three-pulse four-wave mixing. The decay dynamics...
Monolithic integration of 1.3-mym InGaAs photodetectors and HEMT electronic circuits on GaAs (1995)
Fink, T., Hurm, V., Raynor, B., Köhler, K., Benz, W., Ludwig, M.
For the first time, monolithic optoelectronic receivers for a wavelength of 1.3 micrometer have been fabricated successfully on GaAs substrates using InGaAs metalsemiconductor-metal (MSM) photodiodes...
Monolithic integrated optoelectronic circuits for optical links (1995)
Berroth, M., Bronner, W., Fink, T., Hornung, J., Hurm, V., Jakobus, T., ...
Monolithic integrated optoelectronic circuits (1995)
Berroth, M., Bronner, W., Fink, T., Hornung, J., Hurm, V., Jakobus, T., ...
Monolithic integration of lasers and photodetectors with electronic circuits promises higher bandwidth, improved manufacturability, smaller size, lower power and hence lower costs. This paper reviews...
Suski, T., Brunthaler, G., Stöger, G., Köhler, K., Wisniewski, P.
We have examined variation of 2 DEG mobility with carrier concentration, NdeepS, for modulation Delta-doped single quantum well of AlGaAs/GaAs. High concentration of remote Si donors results in...
Laser emission in indirect-gap AlxGa1-xAs (1995)
Westphäling, R., Wörner, A., Kalt, H., Köhler, K.
For the first time we demonstrate optically pumped laser emission up to room temperature related to elctrone-hole-recombination at the indirect fundamental bandgap in Aldeepx Gadeep1-x As.
Hu, C.M., Batke, E., Köhler, K., Ganser, P.
We report here the first observation of the cyclotron resonance Landau splitting for low density electron inversion layers in Alx Ga1-x As-GaAs heterojunctions. Even at temperatures close to 100 K...
Four-wave-mixing theory beyond the semiconductor Bloch equations (1995)
Axt, V.M., Stahl, A., Mayer, E.J., Haring Bolivar, P., Nüsse, S., Ploog, K., ...
Four-wave-mixing (FWM) experiments using a dynamical density matrix model of the semiconductor band edge are discussed. Higher-order correlation functions are retained which arc neglected in the...
External-field-induced electric dipole moment of biexcitons in a semiconductor (1995)
Leisching, P., Ott, R., Haring Bolivar, P., Dekorsy, T., Bakker, H.J., Roskos, H.G., ...
We report on the observation of an electric-field-induced electric dipole moment of biexcitonic molecules in a GaAs/Al0.3Ga0.7As superlattice. The macroscopic oscillating electric field, associated...
Beck, W., Leisching, P., Kurz, H., Schaefer, W., Leo, K., Köhler, K.
Summary form only given. Time-resolved four-wave mixing (TRFWM) has been extensively used to study the influence of Coulomb interactions on the free induction decay of excitons in semiconductor...
Exceptionally slow dephasing of electronic continuum states in a semiconductor (1995)
Leisching, P., Dekorsy, T., Bakker, H.J., Kurz, H., Köhler, K.
The coherent excitation of excitonic and continuum Wannier-Stark states in a semiconductor superlattice with femtosecond laser pulses leads to a modulation of both the interband and the intraband...
Electron g factor in quantum wells determined by spin quantum beats (1995)
Hannak, R.M., Oestreich, M., Heberle, A.P., Rühle, W.W., Köhler, K.
Spin quantum beats are detected in GaAs/Al subx Ga sub1-x As quantum wells in a magnetic field perpendicular to the growth direction by picosecond time-resolved photoluminescence spectroscopy. We...
Elastic contants and Poisson ratio in the system AlAs-GaAs (1995)
Herres, N., Köhler, K., Krieger, M., Sigg, H., Bachem, K.H.
Near infrared Brillouin scattering was used to determine all three elastic constants, and hence Poisson's ratio v=C12/(C11 plus C12) of epitaxial Al(ind x)Ga(ind 1-x)As layer on GaAs. The Al(ind...
Compact high gain low 60 to 80 GHz amplifiers on GaAs (1995)
Braunstein, J., Tasker, P.J., Schlechtweg, M., Maßler, H., Hülsmann, A., Köhler, K., ...
Very compact 2-stage narrow band LNAs with more than 20dB gain between 60 and 80 GHz have been fabricated using cascodes as active elements. On wafer S-parameter measurements showed a maximum gain...
Coherent exciton-photon dynamics in single, double, and quintuple quantum wells. (1995)
Weber, D., Feldmann, J., Göbel, E.O., Citrin, D.S., Köhler, K.
We have studied experimentally the coherent exciton-photon dynamics in a single, a double, and a quintuple quantum well structure under resonant excitation. In pump and probe experiments we observe...
Coherent dynamics of excitonic and biexcitonic wave packets in semiconductor superlattices (1995)
Leisching, P., Ott, R., Bolivar, P.H., Dekorsy, T., Bakker, H.J., Roskos, H.G., ...
We report on the observation of an electric-field-induced electric-dipole moment of biexcitonic molecules in a GaAs/Al0.3Ga0.7As superlattice. The macroscopic oscillating electric field, associated...
Bloch oscillations in semiconductor superlattices (1995)
Roskos, H.G., Waschke, C., Victor, K., Köhler, K., Kurz, H.
A brief summary of the time-resolved investigation of Bloch oscillations of electron wave packets in semiconductor superlattices is given. Focussing on the emission of coherent terahertz-frequency...
Bloch oscillations at room temperature (1995)
Dekorsy, T., Ott, R., Kurz, H., Köhler, K.
We report on the observation of coherent electronic wave-packet oscillations in a semiconductor heterostructure at room temperature. Bloch oscillations are excited in a wide-miniband...
Tackeuchi, A., Heberle, A.P., Rühle, W.W., Köhler, K.
Tunneling in asymmetric double quantum wells is studied using time-resolved hotoluminescence. The photoluminescence lineshape and peak position of the narrow quantum well are strongly influenced by...
110 GHz Amplifiers Based on Compact Coplanar W-Band Receiver Technology (1995)
Schlechtweg, M., Haydl, W.H., Braunstein, J., Tasker, P.J., Bangert, A., Reinert, W., ...
The potential of coplanar waveguide technology to build compact system modules Is demonstrated by means of passive and active MMIC components. The realized passive structures comprise a Wilkinson...
30 GHz static frequency divider using a 0.2 mym AlGaAs/GaAs/AlGaAs HEMT technology (1995)
Lang, M., Berroth, M., Rieger-Motzer, M., Hülsmann, A., Hoffmann, P., Kaufel, G., ...
A frequency devider based on AlGaAs/GaAs/AlGaAs quantum well FETs with 0.2 micrometer gate length has been designed and fabricated. The devider can be operated up to 30 GHz with a single-ended input...
17 GHz broadband amplifier with 25 dB gain using a 0.3 mym AlGaAs/GaAs/AlGaAs HEMT technology (1995)
Lang, M., Berroth, M., Rieger-Motzer, M., Hülsmann, A., Hoffmann, P., Kaufel, G., ...
A broadband amplifier chip based on AlGaAs/GaAs/AlGaAs quantum well FETs with 0.3 micrometer gate length has been designed and fabricated. The amplifier can be operated with single-ended or...
17 GHz-bandwidth 17dB-gain 0.3 micrometer-HEMT low power limiting amplifier (1995)
Berroth, M., Hurm, V., Lang, M., Nowotny, U., Hofmann, P., ...
High-speed limiting amplifiers are widely used in data transmission systems. First, limiting amplifiers can be used in die clock recovery circuit including a passive filter (1) to suppress the...
Hurm, V., Lang, M., Berroth, M., Ludwig, M., Fink, T., ...
An OEIC composed of one MSM-photodetector and 750 GaAs QW-HEMTs of 0.3 gm gatelength has been realized for 10 Gb/s optical data links. It includes a broadband transimpedance amplifier and a...
Hurm, V., Benz, W., Berroth, M., Fink, T., Fritzsche, D., Haupt, M., ...
The first 1.3 mym monolithic integrated optoelectronic receiver using an InGaAs MSM photodiode and AlGaAs/GaAS HEMTs grown on a GaAs substrate has been fabicated. At each differntial output the...
Voltage dependence of the optical response of a pseudomorphic HFET-photodetector (1994)
Bangert, A., Rosenzweig, J., Bosch, R., Bronner, W., Köhler, K., Raynor, B.
A pseudomorphic HFET has been used as a photodetector. The optical respnse of such a device was measured in the frequency range from 100 kHz up to 10 GHz. The response of the HFET-photodetector...
Bakker, H.J., Leo, K., Shah, J., Köhler, K.
We present an experimental and theoretical study of the dephasing of heavy-hole excitons in a 70 Angström GaAs/AlxGa1-xAs multiple-quantum-well structure. We measure the time-integrated threepulse...
Time-resolved studies of Bloch oscillations in semiconductor superlattices (1994)
Leisching, P., Dekorsy, T., Waschke, C., Roskos, H.G., Leo, K., Kurz, H., ...
Bloch oscillations in GaAs/AlGaAs superlattices are investigated in a comparative study by time-resolved four-wave mixing, transmittive electro-optic sampling, as well as by THz-emission spectroscopy.
Terahertz Bloch oscillations in semiconductor superlattices (1994)
Dekorsy, T., Leisching, P., Waschke, C., Köhler, K., Leo, K., Roskos, H.G., ...
The coherent excitation of excitonic wavepackets in AlGaAs/GaAs superlattices is investigated in a comparative study employing three different timeresolved optical techniques. The experimental...
Fink, T., Raynor, B., Haupt, M., Köhler, K., Braunstein, J., Hornung, J., ...
We present a process for fabricating lattice-matched InGaAs/InAlAs modulation doped field effect transistors (MODFETs) on InP wafers including molecular beam epitaxial growth of a high electron...
Photocurrent gain mechanisms in metal-semiconductor-metal photodetectors. (1994)
Klingenstein, M., Kuhl, J., Rosenzweig, J., Moglestue, C., Hülsmann, A., Schneider, J., ...
Different gain mechanisms are observed in metal-semiconductor-metal (MSM) photodetectors consisting of coplanar Schottky contacts on a high resistivity GaAs sample. I-V curves taken at different...
Optical response of a pseudomorphic HFET photodetector up to 10 GHz. TH1D-6 (1994)
Bangert, A., Rosenzweig, J., Ludwig, M., Bronner, W., Hofmann, P., Köhler, K.
For the first time, we present experimental results of the optical response of a pseudomorphic heterostructure field effect transistor (HFET) in the frequency range from 100 kHz up to 10 GHz. During...
Weber, J., Köhler, K., Vetterhöffer, J.
Defects generated during the growth process in low temperature grown GaAs are studied by infrared (IR) absorption and low temperature photoluminescence. The growth temperature and As4-pressure during...
On the electron capture kinetics of DX centers in AlxGa1-xAs-Si. (1994)
Stöger, G., Brunthaler, G., Ostermayer, G., Jantsch, W., Wilamowski, Z., Köhler, K.
The measured temperature dependent free carrier concentration in AlsubxGasub1-xAs:Si samples with different doping concentrations is compared with model calculations where we take into account the...
Monolithic integrated 75 GHz oscillator with high output power using a pseudomorphic HFET (1994)
Bangert, A., Schlechtweg, M., Reinert, W., Haydl, W.H., Hülsmann, A., Köhler, K.
Recently, there has been growing interest in MMICs for circuit applications in the 76 to 77 GHz frequency range allocated for automotive systems in Europe. We have designed and fabricated an...
Bronner, W., Hornung, J., Köhler, K., Olander, E.
In this presentation the various technology steps for the monolithic integration of GaAs quantum well lasers with Double Pulse Doped AlGaAs/GaAs/AlGaAs Quantum Well E/D HEMT electronics on a single...
Leisching, P., Bolivar, P.H., Schwedler, R., Leo, K., Kurz, H., Köhler, K., ...
We study Bloch oscillations (BO) in GaAs/AlGaAs superlattices with miniband widths of 19 and 38 meV at various lattice temperatures. In the time domain, we use transient degenerate four-wave mixing...
Internal field dynamics of cohorent Bloch oscillations in supperlattices (1994)
Dekorsy, T., Leisching, P., Beck, W., Ott, R., Dhaibi, Y., Schwedler, R., ...
The dynamics of coherent wavepacket oscillations in GaAs/AlxGa1-xAs superlattices are investigated by transmittive electro-optic sampling (TEOS) with femtosecond time resolution. The internal...
Shah, J., Damen, T.C., Schäfer, W., Pfeiffer, L.N., Köhler, K.
We show the existence of an instantaneous contribution to the time-resolved four-wave mixing (FWM) from GaAs quantum wells near zero time delay ( T = 0), which is very sensitive to the excitation...
Influence of DX center structure on Si modulation delta-doping in AlGaAs/GaAs quantum wells. (1994)
Brunthaler, G., Seto, M., Stöger, G., Ostermayer, G., Köhler, K.
It has been observed that the achievable 2D electron concentration, in delta-doped quantum wells, depends on the Aluminium concentration in the doping region. So far, this behavior was attributed to...
Sanchez-Rojas, J.L., Gonzalez-Sanz, F., Calleja, E., Munoz, E., Hiesinger, P., ...
Thickness effects of the InGaAs channel on photoluminescence and transport properties of delta-doped Al0.3Ga0.7As/In0.3Ga0.7As heterostructures are investigated. The spreading of the Si delta-doping...
Brunthaler, G., Seto, M., Stöger, G., Köhler, K.
The achievable two-dimensional (2D) electron concentration in a delta-doped quantum well depends on the A] content in the doping layer and is considerably lower than the nominal doping concentration....
Gds and fT analysis of pseudomorphic MODFETs with gate lengths down to 0.1 mym (1994)
Braunstein, J., Tasker, P.J., Hülsmann, A., Köhler, K., Bronner, W., Schlechtweg, M.
Developing circuits for higher frequencies requires not only shorter gate lengths (l sub g), but also proper scaling of the epilayer structure. A common problem with reducing only l sub g is...
Femtosecond intersubband relaxation in GaAs quantum wells (1994)
Hunsche, S., Leo, K., Kurz, H., Köhler, K.
We investigate the intersubband relaxation in GaAs quantum wells at room temperature using differential transmission spectroscopy with subpicosecond time resolution. The dynamics of the subband...
Hülsmann, A., Bronner, W., Hofmann, P., Köhler, K., Raynor, B., Schneider, J., ...
A technology for pseudomorphic MODFETs with 160 nm T-gates was developed and combined with a monolithic microwave integrated circuit (MMIC) fabrication process. The realized MODFETs demonstrate...
Hülsmann, A., Bronner, W., Köhler, K., Braunstein, J., Tasker, P.J.
We have developed a technology to fabricate pseudomorphic 0.3micrometer gatelength modulation doped field-effect transistors (MODFETs ) having a brakdown voltage up to 20 Volts. This technology uses...
Experimental realization of the Bloch oscillator in a semiconductor superlattice. (1994)
Waschke, C., Roskos, H.G., Leo, K., Kurz, H., Köhler, K.
We detect the coherent submillimetre-wave radiation from electron Bloch oscillations in a biased GaAs/AlGaAs semiconductor superlattice by time-resolved terahertz (THz) spectroscopy. The emitted THz...
Hunsche, S., Leo, K., Kurz, H., Köhler, K.
We investigate the temporal evolution and the density dependence of exciton bleaching in GaAs/Al (ind x) Ga (ind 1-x) As quantum wells. We find that the carrier-induced reduction of exciton...
Electro-optic detection of Bloch oscillations (1994)
Dekorsy, T., Leisching, P., Köhler, K., Kurz, H.
The coherent motion of electronic wave packets in the Wannier-Stark regime of externally biased GaAs/Al (ind x) Ga (ind 1-x) As superlattices is investigated by a time-resolved electro-optic...
Kuball, M., Kelly, M.K., Cardona, M., Köhler, K., Wagner, J.
Using rotating analyzer ellipsometry, we determined at room temperature and at 30 K the doping dependence of the E1 and E1 plus Delta1 critical points of n-type highly Si-doped GaAs(100) (up to...
Direct observation of resonant tunneling dynamics in high magnetic fields (1994)
Heberle, A.P., Oestreich, M., Haacke, S., Rühle, W.W., Maan, J.C., Köhler, K.
Magnetotunneling of electrons in an asymmetric double quantum well is investigated by time-resolved luminescence spectroscopy. The tunneling time decreases strongly when the bottom of the lowest...
Waschke, C., Leisching, P., Bolivar, P.H., Schwedler, R., Brüggemann, F., Roskos, H.G., ...
We have studied the spatial dynamics of coherently excited wave packets of charge carriers in a semiconductor superlattice structure by both time-resolved THz spectroscopy and degenerate four-wave...
Heberle, A.P., Zhou, X.Q., Tackeuchi, A., Rühle, W.W., Köhler, K.
We investigated resonant tunnelling of electrons and holes between coupled quantum wells using time-resolved luminescence spectroscopy. Exponential dependence of tunnelling times on barrier width is...
Circumferential arrays used for UT endoscopy on heat exchanger tubes (1994)
Liebig, V., Köhler, K., Gebhardt, W., Kröning, M., Mummert, K.
Bloch oscillations of excitonic wave packets semiconductor superlattices (1994)
Leisching, P., Haring Bolivar, P., Beck, W., Dhaibi, Y., Brüggemann, F., Schwedler, R., ...
We present a detailed investigation of the coherent dynamics of excitonic wave packets composed of heavy/light-hole, electron miniband, and Wannier-Stark states in GaAs/Al subx Ga sub1-x As...
Bloch oscillations in superlattices (1994)
Leisching, P., Waschke, C., Bolivar, P.H., Beck, W., Roskos, H., Leo, K., ...
We have demonstrated the possibility of a Bloch oscillator emitting bias tunable submillimeter-wave radiation. The tuning range covers about one order of magnitude from 0.5 up to 5 THz, with the...
Bloch oscillations in GaAs/AlGaAs superlattices after excitation well above the bandgap (1994)
Roskos, H.G., Waschke, C., Schwedler, R., Leisching, P., Dhaibi, Y., Kurz, H., ...
Bloch oscillations of wave packets in semiconductor superlattices are observed by THz-emission spectroscopy after pulsed photo-excitation well above the fundamental band-gap. We show that Bloch...
20 Gb/s monolithic integrated clock recovery and data decision (1994)
Berroth, M., Hurm, V., Lang, M., Hofmann, P., Hülsmann, A., ...
An IC for 20 Gb/s clock recovery and data decision was realised using 0.3 micrometers gate-length QW-HEMTs. A narrow-band regenerative frequency divider with on-chip resonator filters is used for the...
Berroth, M., Nowotny, U., Hofmann, P., Hülsmann, A., Köhler, K., ...
A monolithically integrated clock recovery (CR) circuit making use of the phase-locked loop (PLL) circuit technique and enhancement/depletion AlGaAs/GaAs quantum well-high electron mobility...
Hurm, V., Benz, W., Berroth, M., Fink, T., Fritzsche, D., Haupt, M., ...
The first 1.3 mym monolithic integrated optoelectronic receiver using an InGaAs MSM photodiode and AlGaAs/GaAS HEMTs grown on a GaAs substrate has been fabicated. At each differntial output the...
Hülsmann, A., Mühlfriedel, E., Raynor, B., Glorer, K., Bronner, W., Köhler, K., ...
Pseudomorphic AlGaAs/InGaAs/GaAs modulation doped FETs (Psi-MODFETs) with sub quarter micron gate length are used in millimeter-wave amplifiers. To reduce the noise figure and enhance the cut-off...
Cell elongation, turgor and osmotic pressure in developing sunflower hypocotyls (1994)
The relationship between cell elongation, change in turgor and cell osmotic pressure was investigated in the sub-apical region of hypocotyls of developing sunflower seedlings (Helianthus annuus L.)...
Very broadband distributed amplifier to 75 GHz. (1993)
Braunstein, J., Tasker, P.J., Hülsmann, A., Schlechtweg, M., Köhler, K., Bronner, W., ...
Distributed amplifiers were fabricated successfully with a gain of 8 dB plusminus 1 dB in the frequency range 5 - 75 GHz measured on-wafer. The associated input and output matching is better than -...
Very broad band TWAs to 80 GHz on GaAs substrate (1993)
Braunstein, J., Tasker, P.J., Hülsmann, A., Schlechtweg, M., Reinert, W., Köhler, K., ...
Traveling Wave Amplifiers were fabricated successfully with a gain of 9.3 dB + 0.6 dB in the frequency range from 5 GHz to 80 GHz measured on-wafer. The associated input and output matching are...
Brunthaler, G., Stöger, G., Aumayr, A., Köhler, K.
A new time-dependent Hall effect analysis method is demonstrated on the DX center in AlGaAs:Si. Due to the time dependence of the carrier concentration and the mobility in the metastable temperature...
Terahertz radiation from coherent electron oscillations in a double-quantum-well structure. (1993)
Roskos, H.G., Nuss, M.C., Shah, J., Leo, K., Miller, D.A.B., Schmitt-Rink, S., ...
We detect the submillimeter-wave radiation from excitonic wave packets that, after excitation by an ultrashort laser pulse, oscillate coherently between the two wells of a semiconductor...
Temperature-dependent cyclotron resonances in n-type GaAs (1993)
Batke, E., Bollweg, K., Merkt, U., Hu, C.M., Köhler, K., Ganser, P.
We report temperature-dependent cyclotron resonances of electrons in bulk GaAs in a temperature regime from about 10-300 K. Due to the nonparabolicity of the GaAs conduction band at sufficiently high...
Stability of an AlGaAs/GaAs/AlGaAsE/D-HEMT process with double pulse doping (1993)
Jakobus, T., Bronner, W., Hofmann, P., Hülsmann, A., Kaufel, G., Köhler, K., ...
The yield of our process sequence for the fabrication of integrated circuits is dominated by the HEMT quality which depends mainly on MBE growth e-beam lithography and dry etching. We report on the...
Relating mym-wave mapped data to physical parameters for MODFETs. (1993)
Braunstein, J., Tasker, P.J., Schlechtweg, M., Hülsmann, A., Kaufel, G., Köhler, K.
Modulation doped Alsub0.2Gasub0.8As/Insub0.3Gasub0.7As high electron mobility transistors (HEMT) were statistically characterized at my-wave frequencies. The results provided information to optimize...
Ramsteiner, M., Hiesinger, P., Köhler, K., Rössler, U., Wagner, J.
Heavily silicon-doped GaAs grown by molecular beam epitaxy has been studied by combined coupled plasmon-phonon mode Raman spectroscopy and Hall effect measurements. Free electron concentrations up to...
Quantum beats versus polarization interference - an experimental distinction (1993)
Koch, M., Feldmann, J., Plessen, G. Von, Göbel, E.O., Thomas, P., Köhler, K.
We report the first experimental distinction between quantum beats and polarization interference of independent quantum mechanical systems by time-resolving the four-wave mixing signal emitted from...
Optical spectroscopy of shallow impurity states in semiconductor quantum wells. (1993)
Monemar, B., Holtz, P.O., Harris, C.I., Bergmann, J.P., Kalt, H., Sundaram, M., ...
Shallow impurities in AlGaAs/GaAs quantum wells, doped with donors or acceptors in the well, are discussed in relation to recent experimental data from optical spectroscopy. Results from two-particle...
Optical investigation of delta-doped In0.1Ga0.9As-Si/GaAs strained quantum wells. (1993)
Richards, D., Maier, M., Köhler, K., Wagner, J.
Photoluminescence and Raman spectroscopy have been used to study a Delta-doped Insub0.1Gasub0.9As:Si/GaAs strained quantum well with the doping spike placed at the centre of the 30 nm wide well. In...
Wagner, J., Behr, D., Richards, D., Bickl, T., Forchel, A., Emmerling, M., ...
We report on the fabrication and photoluminescence characterisation of n-type doped quantum wires, which are based on a modulation-doped GaAs/(InGa)As/(AlGa)As quantum well structure, as used in...
Optical control of pseudomorphic HEMT-based MMIC oscillators. (1993)
Bangert, A., Rosenzweig, J., Hülsmann, A., Kaufel, G., Köhler, K., Schneider, J.
Experimental results on direct and indirect optically controlled monolithically integrated oscillators will be presented. The oscillators had a free-running frequency around 7 GHz. The experimental...
Observation of Bloch oscillations in a semiconductor superlattice (1993)
Haring Bolivar, P., Leisching, P., Leo, K., Shah, J., Köhler, K.
We investigate the polarization decay in biased superlattices with transient degenerate four-wave mixing. The signals have a strong periodic modulation in the field regime where the cw optical...
MODFET technology optimization for MMICs using statistical microwave characterization (1993)
Braunstein, J., Tasker, P.J., Hülsmann, A., Köhler, K., Kaufel, G., Schlechtweg, M.
77 GHz LNAs and TWAs operating from DC to 80 GHz were fabricated successfully (1),(2) using a highly reproducible MODFET technology with mushroom gates of 0.16 mym length. Technology development and...
Investigation of DX centers in AlxGa1-xAs by space charge spectroscopy. (1993)
Wöckinger, J., Jantsch, W., Wilamowski, Z., Köhler, K.
We present a critical analysis of both deep level transient spectroscopy and transient microwave absorption spectroscopy (MAS) for the case of DX centers in AlGaAs. We show that, even for a single...
Integration of a quantum well laser with AlGaAs/GaAs-HEMT electronics. (1993)
Bronner, W., Hornung, J., Köhler, K., Olander, E.
In this presentation the various technology steps for the monolithic integration of GaAs quantum well lasers with Double Pulse Doped AlGaAs/GaAs/AlGaAs Quantum Well (DPD-QW) E/D HEMT electronics on a...
Berroth, M., Nowotny, U., Ludwig, M., Hofmann, P., Hülsmann, A., ...
An integrated laser-diode voltage driver (LDVD) making use of enhancement/depletion AlGaAs/GaAs quantum-well high electron mobility transistors (QW-HEMT's) with gate lengths of 0.3 mym has been...
Hydrogen passivation of shallow impurities in GaAs/AlGaAs quantum wells. (1993)
Harris, C.I., Stutzmann, M., Köhler, K.
The use of hydrogen to passivate defect states in semiconductors has received considerable recent attention. We report in this work on the passivation of Si shallow donors in GaAs/AlGaAs single...
High performance narrow and wide bandwidth amplifiers in CPW-technology up to W-band (1993)
Braunstein, J., Schlechtweg, M., Tasker, P.J., Reinert, W., Hülsmann, A., Köhler, K., ...
Several millimeter-wave MMICs were fabricated successfully using 0.16 mym pseudomorphic MODFET technology. A 5-stage distributed amplifier has 9.3 dB gain over the frequency range 5 GHz to 80 GHz and...
High gain 70-80 GHz MMIC amplifiers in coplanar waveguide technology. (1993)
Schlechtweg, M., Tasker, P.J., Reinert, W., Braunstein, J., Haydl, W.H., Hülsmann, A., ...
Pseudomorphic MODFET three-stage MMIC amplifiers were designed and fabricated which cover the 76-77 GHz band allocated for automotive applications in Europe. The MMICs in coplanar technology have a...
Gds analysis of pseudomorphic MODFETs on GaAs substrate with lg down to 0.1 mym. (1993)
Braunstein, J., Tasker, P.J., Hülsmann, A., Köhler, K., Bronner, W., Schlechtweg, M.
A set of pseudomorphic MODFETs with different epilayer structures and gate lengths between 1 mym and 0.1 mym was investigated. Functional dependencies wee derived to allow further gate length...
Fabrication and performance of 1-dim MODFETs. (1993)
Hülsmann, A., Roman, P., Braunstein, J., Kaufel, G., Köhler, K., Jakobus, T.
We fabricated GaAs/AlGaAs MODFETs having extremely small channels in parallel perpendicular to the gate. The single channel width was varied from 250 nm down to 40 nm, and the pitch was 500 nm. These...
Hendorfer, G., Seto, M., Ruckser, H., Jantsch, W., Helm, M., Brunthaler, G., ...
We present investigations on the in-plane effective mass of conduction electrons in pseudomorphic, strained GaAs/InsubxGasub1minusxAs/AlsubyGasub1minusyAs quantum wells. The samples are modulation...
Harris, C.I., Monemar, B., Kalt, H., Köhler, K.
The development of the photoluminescence spectra with doping density has been studied for a series of single GaAs/AlxGa1-xAs quantum wells center doped with Si. The trends observed are found to be...
Digital dynamic frequency dividers for broad band application up to 60 GHz. (1993)
Thiede, A., Berroth, M., Tasker, P.J., Schlechtweg, M., Seibel, J., Raynor, B., ...
A broad band dynamic frequency divider based on pseudomorphic Al0.2Ga0.8As/In0.25Ga0.75As MODFETs and passive loads wil be presented. Stable operation from 28 GHz up to 51 GHz with a power...
Coupling of exciton transitions associated with different quantum-well islands (1993)
Koch, M., Feldmann, J., Göbel, E.O., Thomas, P., Shah, J., Köhler, K.
We show by means of time-resolved four-wave-mixing experiments that the simultaneous excitation of energetically distinct and inhomogenously broadened exciton transitions associated with spatially...
Maier, M., Köhler, K., Höpner, A., As, D.J.
The thickness of the individual layers of molecular beam epitaxy grown pseudomorphic InsubyGasub1-yAs (0.1equal or smaller than y equal or smaller than 0.35)/GaAs/Alsub0.3Gasub0.7As quantum well...
Comparison of Si delta-doping with homogenous doping in GaAs. (1993)
Köhler, K., Ganser, P., Maier, M.
Homogeneous and Delta-doped GaAs:Si, has been grown by moleclar beam epitaxy at growth temperatures between 410 and 660 degree C. The doping density varied from 1x10high18 to 1.5x10high20 cmhigh-3...
Coherent submillimeter-wave emission from Bloch oscillations in a semiconductor superlattice (1993)
Waschke, C., Roskos, H.G., Schwedler, R., Leo, K., Kurz, H., Köhler, K.
We directly detect the coherent electromagnetic radiation originating from Bloch oscillations of charge carriers in an electrically biased semiconductor superlattice structure. The oscillation...
Auger recombination in intrinsic GaAs (1993)
Strauss, U., Rühle, W.W., Köhler, K.
The recombination kinetics of the electron-hole plasma in strongly excited, intrinsic GaAs is investigated at room temperature by time-resolved photoluminescence using a line-shape analysis of...
Thiede, A., Tasker, P.J., Hülsmann, A., Köhler, K., Bronner, W., Schlechtweg, M., ...
The design and performance of a 28 - 51 GHz dynamic frequency divider based on pseudomorphic Alsub0.2Gasub0.8As/Insub0.25Gasub0.75As MODFETs with 0.15Mym mushroom-shaped gates are presented. The...
Hurm, V., Ludwig, M., Rosenzweig, J., Benz, W., Berroth, M., Bosch, R., ...
A monolithic optoelectronic receiver consisting of an MSM photodiode and a two-stage amplifier has been fabricated using an enhancement/depletion 0.3Mym recessed-gate AlGaAs/GaAs HEMT process. The...
Berroth, M., Nowotny, U., Hofmann, P., Hülsmann, A., Köhler, K., ...
A monolithically integrated clock recovery (CR) circuit making use of the phase-locked loop (PLL) circuit technique and enhancement/depletion AlGaAs/GaAs quantum well high electron mobility...
7.4 Gbit/s monolithically integrated GaAs/AlGaAs laser diode-laser driver structure. (1993)
Hornung, J., Bronner, W., Olander, E., Köhler, K., Ganser, P., ...
A molecular beam epitaxy (MBE) grown (GaAs/AlGaAs multiquantum well laser, monolithically integrated with a laser driver, was realised on 2 inch GaAs substrate wafers. In an optical data...
Schäfer, W., Jahnke, F., Damen, T.C., Köhler, K., Schmitt-Rink, S., ...
Four-wave-mixing signals from excitions in high-quality GaAs quantum wells show an unusually slow temporal evolution, in stark contrast to the behavior expected for a noninteracting two-level system....
Ultrafast metal-semiconductor-metal photodiodes fabricated on low-temperature GaAs. (1992)
Klingenstein, M., Kuhl, J., Nötzel, R., Hülsmann, A., Schneider, J., Köhler, K., ...
GaAs metal-semiconductor-metal photodiodes fabricated on GaAs grown at low substrate temperatures (200 degree C) have been investigated in the time domain by electro-optic sampling. It could be shown...
Ultrafast dephasing in GaAs and GaAs/AlGaAs quantum wells (1992)
Leo, K., Haring Bolivar, P., Maidorn, G., Kurz, H., Köhler, K.
We study the dephasing of excitions and free carriers in GaAs bulk and quantum well samples. The nonlinear response is dominated by the excitionic transitions, which have a room temperature dephasing...
Tunneling through single AlGaAs barriers (1992)
Heberle, A.P., Rühle, W.W., Köhler, K.
Tunneling transfer through Alsub0.35Gasub0.65As barriers is studied in asymmetric double quantum well structures by time-resolved photoluminescence measurements in the pico- and femtosecond regime. A...
Tunneling of electrons and holes in asymmetric double quantum well structures. (1992)
Kuhl, J., Strobel, R., Eccleston, R., Köhler, K.
Simultaneous measurements of electron and hole tunnelling times, and the exciton formation rate in asymmetric double quantum well structures are achieved by the nonlinear double-pulse...
Tunneling between quantum wells. (1992)
Heberle, A.P., Rühle, W.W., Köhler, K.
Tunneling transfer in various GaAs/Alsub0.35Gasub0.65As asymmetric double quantum well structures is studied by time-resolved photoluminescence measurements in the pico- and femtosecond regime. A...
Time-resolved four-wave mixing in GaAs/AlAs quantum well structures. (1992)
Koch, M., Feldmann, J., Plessen, G. Von, Meier, T., Schulze, A., Thomas, P., ...
Femtosecond nonlinear laser spectroscopy is applied to study the dynamics of coherent optical excitations in semiconductors. In particular, excitonic excitations in quantum wells and superlattice...
Temperature-induced spin reversal in n-GaAs. (1992)
Batke, E., Bollweg, K., Merkt, U., Ganser, P., Köhler, K.
Free and bound electrons in bulk GaAs are investigated by cyclotron resonance in the freeze out regime at temperatures below 40 K. A temperature-induced reversal of the relative intensities of the...
Subpicosecond spectroscopy of excitons in GaAs/AlGaAs heterostructures (1992)
Leo, K., Shah, J., Schmitt-Rink, S., Köhler, K.
We study the dynamics of excitons in GaAs/AlGaAs quantum wells using time-resolved self-diffracted four-wave-mixing. We discuss two topics: First, we show that the decay of the diffracted signal is...
Kunzer, M., Hendorfer, G., Köhler, K., Rühle, W.W., Kaufmann, U.
Optical pumping techniques and time-resolved photoluminescence have been used to study spin and exciton lifetimes in two pseudomorphic quantum well systems as a function of well width. From...
Kunzer, M., Hendorfer, G., Kaufmann, U., Köhler, K.
Circularly polarized excitation light from a tunable Ti-doped sapphire laser has been used to produce spin-polarized excitons in strained, pseudomorphic Insub0.16Gasub0.84As/Alsub0.29Gasub0.71As...
Harris, C.I., Kalt, H., Monemar, B., Köhler, K.
The effects of correlation and screening in modulation doped quantum wells have received considerable recent interest. Equivalent interactions have, however, not been discussed for center doped...
Resonant electron and hole tunneling between GaAs quantum wells (1992)
Heberle, A.P., Rühle, W.W., Köhler, K.
Time-resolved photoluminescence measurements in the picosecond regime are reported for a GaAs/Alsub0.35Gasub0.65As asymmetric double quantum well structure biased by electric fields of positive or...
Resonances in tunnelling between quantum wells (1992)
Heberle, A.P., Rühle, W.W., Alexander, M.G.W., Köhler, K.
Time-resolved photoluminescence measurements in the picosecond regime on GaAs/Al0.35 Ga0.65As asymmetric double quantum well structures with perpendicular electric fields applied in both directions...
Raman spectroscopy assessment of laterally structured delta-doped GaAs-Si. (1992)
Hülsmann, A., Kaufel, G., Köhler, K., Wagner, J.
Laterally structured Si Delta-doped GaAs has been investigated by photoluminescence and Raman spectroscopy. Wires were fabricated by electron beam lithography followed by reactive ion mesa etching....
Quantum beats versus polarization interference: An experimental distinction (1992)
Koch, M., Feldmann, J., Plessen, G. Von, Göbel, E.O., Thomas, P., Köhler, K.
We demonstrate that transient four-wave mixing with time-resolved detection of the coherent nonlinear signal allows unambiguous experimental distinction between quantum beats and beats due to...
Quantum beats of excitons in quantum wells (1992)
Schmitt-Rink, S., Damen, T., Göbel, E.O., Köhler, K., Leo, K., Schäfer, W., ...
We review our observations of quantum beats of excitons in quantum wells arising from (i) heavy hole-light hole splitting, (ii) exciton splitting due to fluctuations in the well-width of quantum...
Probing the In mole fraction limits for pseudomorphic MODFETs. (1992)
Braunstein, J., Tasker, P.J., Reinert, W., Schlechtweg, M., Bosch, R., Köhler, K., ...
Modulation doped Alsub0.2Gasub0.8As/InsubyGasub1minussubyAs high electron mobility Transistors (HEMT) were fabricated with In mole fractions in the channel between 0.25 and 0.35 to study the...
Schweizer, T., Ganser, P., Köhler, K.
The electrical properties of Alsub0.3Gasub0.7As/InsubxGasub1minusxAs modulation doped heterostructures grown on GaAs substrates were studied. We found for the normal and inverted heterostructures...
Polarization dependence of heavy- and light-hole quantum beats (1992)
Schmitt-Rink, S., Bennhardt, D., Heuckeroth, V., Thomas, P., Haring, P., Maidorn, G., ...
Simultaneous excitation of heavy- and light-hole quantum-well excitions with linearly polarized ultrashort laser pulses results in oscillating four-wave-mixing and pump-probe signals. These are...
Picosecond photodetectors fabricated on low temperature GaAs (1992)
Klingenstein, M., Kuhl, J., Nötzel, R., Ploog, K., Rosenzweig, J., Moglestue, C., ...
GaAs metal-semiconductor-metal photodiodes fabricated on GaAs grown at low substrate temperatures (200 degree C) have been investigated in the time domain by electro-optic sampling. It could be...
Harris, C.I., Monemar, B., Brunthaler, G., Kalt, H., Köhler, K.
A series of single-quantum-well samples doped with Si in the well (antimodulation), has been investigated using photoluminescence and photoluminescence excitation spectroscopy. The photoluminescence...
Optical spectroscopy of bound excitons in AlGaAs/GaAs quantum wells (1992)
Monemar, B., Holtz, P.O., Bergmann, J.P., Harris, C., Sundaram, M., Merz, J.P., ...
Bound excitons in AlGaAs/GaAs quantum wells, doped with donors or acceptors in the well, are discussed in relation to recent experimental data from optical spectroscopy. Results from two-particle...
Optical dephasing of light-hole excitons in GaAs single quantum wells (1992)
Honold, A., Saku, T., Horikoshi, Y., Köhler, K.
Picosecond photon-echo experiments were performed on light-hole excitons as well as heavy-hole excitons in GaAs single quantum wells at low temperatures and low excitation intensities. The absolute...
Observation of Bloch oscillations in a semiconductor superlattice (1992)
Leo, K., Bolivar, P.H., Brüggemann, F., Schwedler, R., Köhler, K.
We report unambiguous experimental evidence for electron Bloch oscillations: The transient four-wave mixing signal of a biased semiconductor superlattice shows a periodic modulation with a time...