Current-Induced Spin Polarization in Gallium Nitride (2009)
Koehl, W. F., Wong, M. H., Poblenz, C., Swenson, B., Mishra, U. K., Speck, J. S., ...
Electrically generated spin polarization is probed directly in bulk GaN using Kerr rotation spectroscopy. A series of n-type GaN epilayers are grown in the wurtzite phase both by molecular beam...
Microdiffraction imaging of dislocation densities in microstructured samples. (2008)
Lübbert, D., Baumbach, T., Holy, V., Mikulik, P., Helfen, L., Pernot, P., ...
EPL, 82(2008) S.56002/1-2
Anisotropic strain and phonon deformation potentials in GaN (2007)
Darakchieva, V., Paskova, T., Schubert, Mathias, Arwin, H., Paskov, P.P., Monemar, B., ...
We report optical phonon frequency studies in anisotropically strained c-plane- and a-plane-oriented GaN films by generalized infrared spectroscopic ellipsometry and Raman scattering spectroscopy....
Behn, U, Misra, P, Grahn, H T, Imer, B, Nakamura, S, DenBaars, S P, ...
We have used polarized photoreflectance spectroscopy to study the electronic-band-structure modification of GaN films grown along different nonpolar orientations due to biaxial, anisotropic in-plane...
Armstrong, A, Chakraborty, A, Speck, J S, DenBaars, S P, Mishra, U K, Ringel, S A
Deep levels were observed using capacitance deep level optical spectroscopy (DLOS) in an AlGaN/GaN heterostructure equivalent to that of a heterojunction field effect transistor. Band gap states were...
Kamber, D S, Wu, Y, Haskell, B A, Newman, S, DenBaars, S P, Speck, J S, ...
Thick AlN layers were grown directly on sapphire substrates by hydride vapor phase epitaxy at growth rates of 40-60 mu m/h. The resulting films were colorless, smooth and specular. Subsurface...
Quadrupole mass spectrometry desorption analysis of Ga adsorbate on AIN (0001) (2006)
Brown, J S, Koblmuller, G, Averbeck, R, Riechert, H, Speck, J S
The authors have investigated the adsorption and subsequent desorption of Ga on AlN (0001) with line-of-sight quadrupole mass spectrometry (QMS). The authors present desorption data consistent with a...
Excitation wavelength dependence of terahertz emission from InN and InAs (2006)
Chern, G D, Readinger, E D, Shen, H G, Wraback, M, Gallinat, C S, Koblmuller, G, ...
The authors report on the excitation wavelength dependence of terahertz emission from n-InN and bulk p-InAs pumped with femtosecond pulses tunable from 800 to 1500 nm. The terahertz amplitude,...
Optical properties of nonpolar a-plane GaN layers (2006)
Paskov, P P, Paskova, T, Monemar, B, Figge, S, Hommel, D, Haskell, B A, ...
We have studied optical properties of nonpolar a-plane GaN layers grown on r-plane sapphire by metalorganic chemical vapor deposition and hydride vapor phase epitaxy using different nucleation...
Growth of p-type and n-type m-plane GaN by molecular beam epitaxy (2006)
McLaurin, M, Mates, T E, Wu, F, Speck, J S
Plasma-assisted molecular beam epitaxial growth of Mg-doped, p-type and Si-doped, n-type m-plane GaN on 6H m-plane SiC is demonstrated. Phase-pure, m-plane GaN films exhibiting a large anisotropy in...
Koblmuller, G, Gallinat, C S, Bernardis, S, Speck, J S, Chern, G D, Readinger, E D, ...
The authors demonstrate the impact of growth kinetics on the surface and structural properties of N-face InN grown by molecular beam epitaxy. Superior surface morphology with step-flow growth...
Koyama, T, Onuma, T, Masui, H, Chakraborty, A, Haskell, B A, Keller, S, ...
Prospective equivalent internal quantum efficiency (eta(int)) of approximately 34% at 300 K was demonstrated for the blue emission peak of nonpolar m-plane (1 (1) over bar 00) InxGa1-xN/GaN multiple...
Defect reduction in nonpolar a-plane GaN films using in situ SiNx nanomask (2006)
Chakraborty, A, Kim, K C, Wu, F, Speck, J S, DenBaars, S P, Mishra, U K
We report on the use of in-situ SiNx nanomask for defect reduction in nonpolar a-plane GaN films, grown by metal-organic chemical vapor deposition. High-resolution x-ray diffraction analysis revealed...
Effect of threading dislocation density on Ni/n-GaN Schottky diode I-V characteristics (2006)
Arehart, A R, Moran, B, Speck, J S, Mishra, U K, DenBaars, S P, Ringel, S A
The impact of threading dislocation density on Ni/n-GaN Schottky barrier diode characteristics is investigated using forward biased current-voltage-temperature (I-V-T) and internal photoemission...
In-polar InN grown by plasma-assisted molecular beam epitaxy (2006)
Gallinat, C S, Koblmuller, G, Brown, J S, Bernardis, S, Speck, J S, Chern, G D, ...
We study the effect of different deposition conditions on the properties of In-polar InN grown by plasma-assisted molecular beam epitaxy. GaN buffer layers grown in the Ga-droplet regime prior to the...
Strain-induced polarization in wurtzite III-nitride semipolar layers (2006)
Romanov, A E, Baker, T J, Nakamura, S, Speck, J S
This paper presents growth orientation dependence of the piezoelectric polarization of InxGa1-xN and AlyGa1-yN layers lattice matched to GaN. This topic has become relevant with the advent of growing...
Brown, J S, Koblmuller, G, Averbeck, R, Riechert, H, Speck, J S
We have investigated the Ga-adlayer mediated growth of GaN quantum dots at 707 degrees C on AlN (0001) by simultaneous use of in situ reflection high-energy electron diffraction and line-of-sight...
Barabash, R I, Ice, G E, Liu, W, Roder, C, Figge, S, Einfeldt, S, ...
The spatial distribution of strain, dislocations, and crystallographic orientation in uncoalesced and coalesced GaN layers grown on striped Si or SiC substrates was studied by polychromatic X-ray...
Optical polarization anisotropy in strained A-plane GaN films on R-plane sapphire (2006)
Ghosh, S, Misra, P, Grahn, H T, Imer, B, Nakamura, S, DenBaars, S P, ...
We have used polarized photoreflectance (PR) spectroscopy to study [1120]-oriented A-plane GaN films on R-plane sapphire substrates. For this type of films, the c-axis of GaN lies in the film plane....
AlGaN/AlN distributed Bragg reflectors for deep ultraviolet wavelengths (2006)
Moe, C G, Wu, Y, Piprek, J, Keller, S, Speck, J S, DenBaars, S P, ...
Distributed Bragg reflectors with up to 21 periods consisting of AlN and Al0.58Ga0.42N layers were grown by metalorganic chemical vapor deposition. A periodic structure and good interface quality was...
Phase selection of microcrystalline GaN synthesized in supercritical ammonia (2006)
Hashimoto, T, Fujito, K, Sharma, R, Letts, E R, Fini, P T, Speck, J S, ...
Microcrystalline GaN was synthesized in supercritical ammonia with acidic, neutral, and basic mineralizers. For both acidic and neutral mineralizers, a mixture of wurtzite GaN and zinc-blende GaN was...
Strain in a-plane GaN layers grown on r-plane sapphire substrates (2006)
Roder, C, Einfeldt, S, Figge, S, Hommel, D, Paskova, T, Monemar, B, ...
The strain in a-plane GaN layers of different thickness grown on r-plane sapphire substrates by hydride vapor phase epitaxy was studied by X-ray diffraction. The layers are found to be under...
Crystal quality and growth evolution of aluminum nitride on silicon carbide (2006)
Moe, C G, Wu, Y, Keller, S, Speck, J S, DenBaars, S P, Emerson, D
High quality base layer aluminum nitride films have become increasingly desirable with the advent of deep ultraviolet (< 280 nm) emitters for water purification, solid state lighting, and...
Brown, J S, Koblmuller, G, Wu, F, Averbeck, R, Riechert, H, Speck, J S
We have investigated the adsorption and subsequent desorption of Ga on (0001) GaN using simultaneous line-of-sight quadrupole mass spectrometry (QMS) and reflection high-energy electron diffraction...
Recht, F, McCarthy, L, Rajan, S, Chakraborty, A, Poblenz, C, Corrion, A, ...
This letter reports AlGaN/GaN high-electron mobility transistors with capless activation annealing of implanted Si for nonalloyed ohmic contacts. Source and drain areas were implanted with an Si dose...
Misra, P, Behn, U, Brandt, O, Grahn, H T, Imer, B, Nakamura, S, ...
We use photoreflectance (PR) spectroscopy to study the electronic band structure modification of GaN films grown along different nonpolar orientations due to biaxial, anisotropic in-plane strain. The...
Unpassivated high power deeply recessed GaNHEMTs with fluorine-plasma surface treatment (2006)
Shen, L, Palacios, T, Poblenz, C, Corrion, A, Chakraborty, A, Fichtenbaum, N, ...
In this letter, unpassivated high power deeply recessed GaN-based high electron mobility transistors (HEMTs) are reported. The introduction of a thick graded AlGaN cap layer and a novel...
Growth of Fe-doped GaN by RF plasma-assisted molecular beam epitaxy (2006)
Corrion, A, Wu, F, Mates, T, Gallinat, C S, Poblenz, C, Speck, J S
Iron-doped GaN films were grown using plasma-assisted molecular beam epitaxy (PA-MBE) for various III/V ratios. Iron concentrations were determined by calibrated secondary-ion mass spectroscopy...
Onuma, T, Keller, S, DenBaars, S P, Speck, J S, Nakamura, S, Mishra, U K, ...
Recombination dynamics of the 268 nm photoluminescence (PL) peak in a quaternary Al0.53In0.11Ga0.36N/Al0.58In0.02Ga0.40N multiple quantum well (MQW) grown on relaxed AlGaN templates were studied....
Dora, Y, Han, S, Klenov, D, Hansen, P J, No, K S, Mishra, U K, ...
We investigated the suitability of ZrO2 as a high-k dielectric for GaN material systems. Thin Zr films (4 nm) were deposited by electron-beam evaporation at room temperature oil n-type GaN and...
Armstrong, A, Poblenz, C, Green, D S, Mishra, U K, Speck, J S, Ringel, S A
The electrical conductivity and deep level spectrum of GaN grown by molecular beam epitaxy and codoped with carbon and silicon were investigated for substrate temperatures T-s of 650 and 720 degrees...
Improved quality (11(2)over-bar0) a-plane GaN with sidewall lateral epitaxial overgrowth (2006)
Imer, B M, Wu, F, DenBaars, S P, Speck, J S
We demonstrate a technique to reduce the extended defect densities in a-plane GaN deposited on r-plane sapphire. The SiO2 lateral epitaxial overgrowth mask consisted of < 1100 >(GaN) stripes. Both...
Zhou, X, Yu, E T, Green, D S, Speck, J S
Scanning probe techniques including scanning capacitance microscopy, scanning capacitance spectroscopy, scanning Kelvin probe force microscopy, and atomic force microscopy have been used to assess...
Demonstration of a semipolar (10(1)over-bar(3)over-bar) InGaN/GaN green light emitting diode (2005)
Sharma, R, Pattison, P M, Masui, H, Farrell, R M, Baker, T J, Haskell, B A, ...
We demonstrate the growth and fabrication of a semipolar (10 (13) over bar) InGaN/GaN green (similar to 525 nm) light emitting diode (LED). The fabricated devices demonstrated a low turn-on voltage...
High-power AlGaN/GaN HEMTs for Ka-band applications (2005)
Palacios, T, Chakraborty, A, Rajan, S, Poblenz, C, Keller, S, DenBaars, S P, ...
We report on the fabrication and high-frequency characterization of AlGaN/GaN high-electron mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) and metal-organic chemical vapor...
Molecular-beam epitaxy of p-type m-plane GaN (2005)
McLaurin, M, Mates, T E, Speck, J S
We report on the plasma-assisted molecular-beam epitaxy of Mg-doped (10 (1) over bar0) GaN on (10 (1) over bar0) 6H-SiC. Secondary ion mass spectroscopy measurements show the incorporation of Mg into...
Role of inclined threading dislocations in stress relaxation in mismatched layers (2005)
Cantu, P, Wu, F, Waltereit, P, Keller, S, Romanov, A E, DenBaars, S P, ...
(0001)-oriented epitaxial wurtzite III-nitride layers grown on mismatched substrates have no resolved shear stress on the natural basal and prismatic slip planes; however, strained Ill-nitride layers...
Rutile films grown by molecular beam epitaxy on GaN and AlGaN/GaN (2005)
Hansen, P J, Vaithyanathan, V, Wu, Y, Mates, T, Heikman, S, Mishra, U K, ...
Titanium dioxide (TiO2, with the rutile structure) was grown on (0001) oriented GaN and (0001) Al0.33Ga0.67N/GaN heterostructure field effect transistor (HFET) structures by molecular beam epitaxy....
Buried stressors in nitride semiconductors: Influence on electronic properties (2005)
Romanov, A E, Waltereit, P, Speck, J S
An analysis is presented on the effect of the strain field originating from a subsurface stressor (point source of dilatation or a dilatating ellipsoidal inclusion) on the electronic properties of...
Carbon doping of GaN with CBr4 in radio-frequency plasma-assisted molecular beam epitaxy (2004)
Green, D S, Mishra, U K, Speck, J S
Carbon tetrabromide (CBr4) was studied as an intentional dopant during rf plasma molecular beam epitaxy of GaN. Secondary ion mass spectroscopy was used to quantify incorporation behavior. Carbon was...
Andrews, A M, LeSar, R, Kerner, M A, Speck, J S, Romanov, A E, Kolesnikova, A L, ...
We present further developments and understanding of the commonly observed crosshatch surface morphology in strain-relaxed heteroepitaxial films. We have previously proposed that the crosshatch...
Power performance of AlGaN-GaNHEMTs grown on SiC by plasma-assisted MBE (2004)
Rajan, Siddharth, Waltereit, P, Poblenz, C, Heikman, S J, Green, D S, Speck, J S, ...
We report AlGaN-GaN high electron mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) on SiC substrates with excellent microwave power and efficiency performance. The GaN buffers in...
Gao, Yan, Craven, M D, Speck, J S, DenBaars, S P, Hu, E L
Polarity and dislocation dependence study of photoelectrochemical wet etching on GaN was carried out on lateral epitaxial overgrown nonpolar (11 (2) over bar0)a-GaN/(1 (1) over bar 02)r-plane...
Effect of nitridation on polarity, microstructure, and morphology of AlN films (2004)
Wu, Y, Hanlon, A, Kaeding, J F, Sharma, R, Fini, P T, Nakamura, S, ...
The polarity of AlN epitaxial layers grown on (0001) sapphire, SiC, and nitrided sapphire substrates was examined by convergent beam electron diffraction, and the morphology and microstructure were...
GaN quantum dot density control by rf-plasma molecular beam epitaxy (2004)
Brown, J, Wu, F, Petroff, P M, Speck, J S
We report on the growth of GaN quantum dots and the control of their density in the Stranski-Krastanov mode on AlN (0001) by rf-plasma molecular beam epitaxy at 750 degreesC. After depositing the...
Craven, M D, Wu, F, Chakraborty, A, Imer, B, Mishra, U K, DenBaars, S P, ...
This letter describes the relationship between the morphological evolution of heteroepitaxial a-plane GaN films and the formation of the extended defect structure. The initial a-plane GaN growth on...
Miller, E J, Schaadt, D M, Yu, E T, Sun, X L, Brillson, L J, Waltereit, P, ...
Dislocation-related conduction paths in n-type GaN grown by molecular-beam epitaxy and a mechanism for local suppression of current flow along these paths are analyzed using conductive atomic force...
Antimony segregation in the oxidation of AlAsSb interlayers (2003)
Andrews, A M, Van Horn, K L, Mates, T, Speck, J S
The lateral wet oxidation of strained AlAsSb was studied. AlAs0.80Sb0.20 interlayers were grown on a GaAs substrate and capped with a lattice-matched In0.25Ga0.75As layer. The AlAsSb was oxidized...
Winzer, A T, Goldhahn, R, Buchheim, C, Ambacher, O, Link, A, Stutzmann, M, ...
Photoreflectance measurements have been carried out in order to determine the electric field strength F within the topmost layers of Ga-face polarity AlxGa1-xN/GaN and N-face polarity...
Yamamoto, N, Itoh, H, Grillo, V, Chichibu, S F, Keller, S, Speck, J S, ...
Cathodoluminescence technique combined with transmission electron microscopy (TEM-CL) has been used to characterize optical properties of dislocations in GaN epilayers. The dislocations act as...
Taylor, T R, Hansen, P J, Pervez, N, Acikel, B, York, R A, Speck, J S
The dielectric permittivity, dielectric quality factor (inverse dielectric loss), and lattice parameter of 140 nm sputtered SrTiO3 films were dependent on the oxygen partial pressure and total...
Stress relaxation in mismatched layers due to threading dislocation inclination (2003)
A recently observed mechanism of elastic stress relaxation in mismatched layers is discussed. The relaxation is achieved by the inclination of pure edge threading dislocation lines with respect to...
Simpkins, B S, Yu, E T, Waltereit, P, Speck, J S
Scanning Kelvin probe microscopy (SKPM) and conductive atomic force microscopy (C-AFM) have been used to image surfaces of GaN grown by molecular beam epitaxy. Detailed analysis of the same area...
Haskell, B A, Wu, F, Matsuda, S, Craven, M D, Fini, P T, DenBaars, S P, ...
This letter discusses the structural and morphological characteristics of planar, nonpolar (11 (2) over bar0) a-plane GaN films grown on (1 (1) over bar 02) r-plane sapphire by hydride vapor phase...
Haskell, B A, Wu, F, Craven, M D, Matsuda, S, Fini, P T, Fujii, T, ...
This letter reports on the reduction in extended-defect densities in a-plane (11 (2) over bar0) GaN films achieved via lateral epitaxial overgrowth (LEO) by hydride vapor phase-epitaxy. A variety of...
Brandt, O, Sun, Y J, Schonherr, H P, Ploog, K H, Waltereit, P, Lim, S H, ...
We present a simple strategy that minimizes the impact of surface segregation of In during the growth of (In,Ga) N/GaN multiple quantum wells by plasma-assisted molecular-beam epitaxy and...
Polarity control during molecular beam epitaxy growth of Mg-doped GaN (2003)
Green, D S, Haus, E, Wu, F, Chen, L, Mishra, U K, Speck, J S
Mg doping has been found in some situations to invert growth on Ga-face GaN to N-face. In this study, we clarified the role the Ga wetting layer plays in rf plasma molecular beam epitaxy of GaN when...
Wu, F, Craven, M D, Lim, S H, Speck, J S
Achieving nitride-based device structures unaffected by polarization-induced electric fields can be realized with nonpolar GaN, although polarity plays a key role in the growth. (11 (2) over bar0)...
Si doping effect on strain reduction in compressively strained Al0.49Ga0.51N thin films (2003)
Cantu, P, Wu, F, Waltereit, P, Keller, S, Romanov, A E, Mishra, U K, ...
Evaluation of the structural properties of 200-nm-thick Si-doped Al0.49Ga0.51N films, grown on nominally relaxed 1-mum-thick Al0.62Ga0.38N buffer layers on sapphire, revealed that increased Si doping...
Keller, S, Waltereit, P, Cantu, P, Mishra, U K, Speck, J S, DenBaars, S P
280 nm thick Al0.2Ga0.8N/Al0.7Ga0.3N superlattice structures with various well and barrier layer thickness and different silicon doping were grown on 1.2 mum thick Al0.63Ga0.37N-on-sapphire films by...
Polarization effects in AlGaN/GaN and GaN/AlGaN/GaN heterostructures (2003)
Heikman, S, Keller, S, Wu, Y, Speck, J S, DenBaars, S P, Mishra, U K
The influence of AlGaN and GaN cap layer thickness on Hall sheet carrier density and mobility was investigated for Al0.32Ga0.68N/GaN and GaN/Al0.32Ga0.68N/GaN heterostructures deposited on sapphire...
High-quality InAsyP1-y step-graded buffer by molecular-beam epitaxy (2003)
Hudait, M K, Lin, Y, Wilt, D M, Speck, J S, Tivarus, C A, Heller, E R, ...
Relaxed, high-quality, compositionally step-graded InAsyP1-y layers with an As composition of y=0.4, corresponding to a lattice mismatch of similar to1.3% were grown on InP substrates using...
Crystallographic wing tilt in laterally overgrown GaN (2003)
Roder, C, Heinke, H, Hommel, D, Katona, T M, Speck, J S, DenBaars, S P
Thin uncoalesced gallium nitride (GaN) layers grown on Si(111) by maskless cantilever epitaxy (CE) have been investigated using high resolution x-ray diffraction at variable temperatures. The...
High-quality GaN on intentionally roughened c-sapphire (2003)
Golan, Y, Fini, P, Dahan, D, Wu, F, Zamir, S, Salzman, J, ...
GaN films were grown using metal-organic chemical vapor deposition (MOCVD) on intentionally roughened c-sapphire in order to study the effect of the substrate roughness. Controlled substrate damage...
Jena, D, Heikman, S, Speck, J S, Gossard, A, Mishra, U K, Link, A, ...
Shubnikov-de-Haas oscillation is observed in a polarization-doped three-dimensional electron slab in a graded AlxGa1-xN semiconductor layer. The electron slab is generated by the technique of grading...
Miller, E J, Schaadt, D M, Yu, E T, Waltereit, P, Poblenz, C, Speck, J S
An electrochemical surface treatment has been developed that decreases the reverse-bias leakage current in Schottky diodes fabricated on GaN grown by molecular-beam epitaxy (MBE). This treatment...
Sun, Y J, Brandt, O, Cronenberg, S, Dhar, S, Grahn, H T, Ploog, K H, ...
M-plane In0.1Ga0.9N(1 (1) over bar 00) multiple quantum wells were grown on gamma-LiAlO2(100) by plasma-assisted molecular-beam epitaxy. The high brightness of the photoluminescence of these multiple...
Magnetotransport properties of a polarization-doped three-dimensional electron slab (2002)
Jena, D., Heikman, S., Speck, J. S., Gossard, A. C., Mishra, U. K., Link, A., ...
We present evidence of strong Shubnikov-de-Haas magnetoresistance oscillations in a polarization-doped degenerate three-dimensional electron slab in an Al$_{x}$Ga$_{1-x}$N semiconductor system. The...
Microstructure of Thin Intercalated Benezene Derived Graphite Fibers. (1998)
Minami, E., Dresselhaus, M. S., Hao, X., Speck, J. S., Endo, M.
A brief study has been carried out to investigate the structure of pristine and intercalated thin benzene derived graphite fibers. High resolution transmission electron microscopy techniques were...
Electronic and Structural Studies of Carbon/Carbon Composites, (1998)
Doll, G. L., Sakya, R. M., Nicholls, J. T., Speck, J. S., Dresselhaus, M.S.
Room temperature Raman microprobe x-ray diffraction and electrical resistivity measurements have been performed on carbon/carbon composites made from mesophase pitch which were heat treated at...
Olson, G. L., Roth, J. A., De Lyon, T. J., Jensen, J. E., Speck, J. S.
This report presents the results of research on compliant substrate behavior in III-V semiconductors grown by molecular beam epitaxy (MBE) on thin (50-80A) InGaAs layers on GaAs, and in II-VI...
The Mechanical Properties of CVD Diamond. (1998)
Drory, M. D., Gardinier, C. F., Pinneo, J. M., Speck, J. S.
The fracture toughness of CVD diamond is measured by the Vickers indentation method. Free standing diamond films of 400 micron thickness are produced with plasma-enhanced chemical vapor deposition,...
Pompe, W., Gong, X., Suo, Z., Speck, J. S.
Twin related domain formation is examined as a strain relaxation mechanism for a heteroepitaxial tetragonal film on a cubic substrate. Elastic relaxations are calculated for a single twin band in...
Srikant, V., Tarsa, E. J., Clarke, D. R., Speck, J. S.
Epitaxial ferroelectric BaTiO3 thin films have been grown on (001) MgO and MgO-buffered (001) GaAs substrates by pulsed laser deposition to explore the effect of substrate lattice parameter....