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551.  Aluminum free GaInP/GaAs Quantum Well Infrared Photodetectors for Long Wavelength Detection
C. Jelen, S. Slivken, J. Hoff, M. Razeghi, and G. Brown
Applied Physics Letters 70 (3)-- January 20, 1997
We demonstrate quantum well infrared photodetectors based on a GaAs/Ga0.51In0.49P superlattice structure grown by gas-source molecular beam epitaxy. Wafers were grown with varying well widths. Wells of 40, 65, and 75 Å resulted in peak detection wavelengths of 10.4, 12.8, and 13.3 μm with a cutoff wavelength of 13.5, 15, and 15.5 μm, respectively. The measured peak and cutoff wavelengths match those predicted by eight band theoretical analysis. Measured dark currents were lower than equivalent GaAs/AlGaAs samples. reprint
552.  InAsSbP/InAsSb/InAs Laser Diodes λ = 3.2 μm) Grown by Low-Pressure Metalorganic Chemical Vapor Deposition
J. Diaz, G. Lukas, D. Wu, S. Kim, M. Erdtmann, E. Kaas, and M. Razeghi
Applied Physics Letters 70 (1)-- January 6, 1997
We report metal–organic chemical-vapor deposition-grown double heterostructure InAsSbP/InAsSb/InAs diode lasers emitting at 3.2 μm operating at temperatures up to 220 K with threshold current density of 40 A/cm² at 77 K and characteristic temperature up to 42 K. Output powers as high as 260 mW in pulse mode and 60 mW in continuous wave operation have been obtained from an uncoated 100 μm stripe-width broad-area laser at 77 K. Comparison with theory shows that there is no significant nonradiative recombination mechanism for these lasers at 77 K. reprint
553.  Infrared Imaging Arrays Using Advanced III-V Materials and technology
M. Razeghi, J.D. Kim, C. Jelen, S. Slivken, E. Michel, H. Mohseni, J.J. Lee, J. Wojkowski, K.S. Kim, H.I. Jeon, and J. X
IEEE Proceedings, Advanced Workshop on Frontiers in Electronics (WOFE), Tenerife, Spain;-- January 6, 1997
Photodetectors operating in the 3-5 and 8-12 μm atmospheric windows are of great importance for applications in infrared (IR) thermal imaging. HgCdTe has been the dominant material system for these applications. However, it suffers from instability and non-uniformity problems over large areas due to high Hg vapor pressure during the material, growth. There has been a lot of interest in the use of heteroepitaxially grown Sb-based alloys, its strained layer superlattices, and GaAs based quantum wells as alternatives to MCT. This interest has been driven by the advanced material growth and processing technology available for the III-V material system reprint
554.  Epitaxial growth models of hexagonal and cubic GaN on (100) Si substrates
H. Ohsato, T. Kato, M. Razeghi, and T. Okuda
-- January 1, 1997
555.  Morphology of Twinned GaN Grown on (11.0) Sapphire Substrates
T. Kato, P. Kung, A. Saxler, C.J. Sun, H. Ohsato, M. Razeghi and T. Okuda
-- January 1, 1997
556.  Simultaneous growth of two different oriented GaN epilayers on (11.0) sapphire (I) morphology and orientation
T. Kato, H. Ohsato, T. Okuda, P. Kung, A. Saxler, C.J. Sun, and M. Razeghi
-- January 1, 1997
557.  MOCVD Growth of High Quality GaN-AlGaN Based Structures on Al2O3 Substrates with Dislocation Density less than 107cm-2
P. Kung, X. Zhang, A. Saxler, D. Walker, M. Razeghi, W. Qian, and V.P. Dravid
-- January 1, 1997
558.  Gas Source Molecular Beam Epitaxy Growth and Characterization of Ga0.51In0.49P/InxGa1-xAs/GaAs Modulation-doped Field-effect Transistor Structures
C. Besikci, Y. Civan, S. Ozder, O. Sen, C. Jelen, S. Slivken, and M. Razeghi
Semiconductor Science Technology 12-- January 1, 1997
Lattice-matched Ga0.51In0.49P/GaAs and strained Ga0.51In0.49P/InxGa1−xAs/GaAs (0.1 ≤ x ≤ 0.25) modulation-doped field-effect transistor structures were grown by gas source molecular beam epitaxy by using Si as dopant. Detailed electrical characterization results are presented. The Ga0.5In0.49P/In0.25Ga0.75As/GaAs sample yielded dark two-dimensional electron gas densities of 3.75 x 1012 cm-2 (300 K) and 2.3 x 1012 cm-2 (77 K) which are comparable to the highest sheet electron densities reported in AlGaAs/InGaAs/GaAs and InAlAs/InGaAs/InP modulation-doped heterostructures. Persistent photoconductivity was observed in the strained samples only. A 0.797 eV deep level has been detected in the undoped GaInP layers of the structures. Another level, with DLTS peak height dependent on the filling pulse width, has been detected at the interface of the strained samples. Based on the DLTS and Hall effect measurement results, this level, which seems to be the origin of persistent photoconductivity, can be attributed to the strain relaxation related defects. reprint
559.  High Power InAsSb/InAsSbP Laser Diodes Emitting at 3-5 μm Range
M. Razeghi, J. Diaz, H.J. Yi, D. Wu, B. Lane, A. Rybaltowski, Y. Xiao, and H. Jeon
-- December 2, 1996
560.  GaAs/GaInP Quantum Well Intersubband Photodetectors for Focal Plane Array Infrared Imaging
C. Jelen, S. Slivken, G.J. Brown, and M. Razeghi
-- December 2, 1996
561.  InSb Detectors and Focal Plane Arrays on GaAs, Si, and Al2O3 Substrates
E. Michel, H. Mohseni, J. Wojkowski, J. Sandven, J. Xu, M. Razeghi, P. Vu, R. Bredthauer, W. Mitchel, and M. Ahoujja
-- December 2, 1996
562.  High Resolution X-ray Diffraction of GaN Grown on Sapphire Substrates
A. Saxler, M.A. Capano, W.C. Mitchel, P. Kung, X. Zhang, D. Walker and M. Razeghi
-- December 2, 1996
563.  AlGaN Based Materials and Heterostructures
P. Kung, A. Saxler, D. Walker, X. Zhang, R. Lavado, K.S. Kim, and M. Razeghi
-- December 2, 1996
564.  Observation of Room Temperature Surface-Emitting Stimulated Emission from GaN:Ge by Optical pumping
X. Zhang, P. Kung, A. Saxler, D. Walker, and M. Razeghi
Journal of Applied Physics 80 (11)-- December 1, 1996
Optically pumped surface-emitting stimulated emission at room temperature was observed from GaN:Ge grown by metalorganic chemical vapor deposition. The sample was optically pumped perpendicularly on the top surface while the stimulated emission was collected from the back colinearly with the pump beam. The cavity was formed by the GaN/air and GaN/sapphire interfaces without any other structure. The stimulated emission was gain guided by the pump beam. The threshold optical pump density for stimulated emission was approximately 2.8 MW/cm² and the linewidth was 2.5 nm. The emission from GaN:Ge showed a redshift as the pump density increased. The comparison between theoretical calculations and experimental results suggested that many-body interactions can account well for the redshift. reprint
565.  Optical losses of Al-free lasers for λ = 0.808 and 0.98 μm
H. Yi, J. Diaz, B. Lane, and M. Razeghi
Applied Physics Letters 69 (20)-- November 11, 1996
In this work, we study the origin of the optical losses in Al‐free InGaAsP/GaAs (λ=0.808 μm) and InGaAs/GaAs/InGaP (λ=0.980 μm) lasers. Theoretical modeling and the experimental results indicate that the scattering of the laser beam by refractive index fluctuation in the alloys is the dominant loss in our lasers, and the loss due to the free‐carrier absorption and scattering by interface roughness are negligible. reprint
566.  Effect of the spin split-off band on optical absorption in p-type Ga1 xInxAsyP1-y quantum-well infrared detectors
J.R. Hoff, M. Razeghi and G. Brown
Physical Review B 54 (15)-- October 15, 1996
Experimental investigations of p-type Ga1-xInxAsyP1-y quantum-well intersubband photodetectors (QWIP’s) led to the discovery of unique features in photoresponse spectra of these devices. In particular, the strong 2–5 μm photoresponse of these QWIP’s was not anticipated based on previous experimental and theoretical results for p-type GaAs/AlxGa1-xAs QWIP’s. Our theoretical modeling of p-type QWIP’s based on the Ga1-xInxAsyP1-y system revealed that the intense short-wavelength photoresponse was due to a much stronger coupling to the spin-orbit split-off components in the continuum than occurs for GaAs/AlxGa1-xAs QWIP’s. Due to the strong influence of the spin split-off band, an eight-band Kane Hamiltonian was required to accurately model the measured photoresponse spectra. This theoretical model is first applied to a standard p-type GaAs/Al0.3Ga0.7As QWIP, and then to a series of GaAs/Ga0.51In0.49P, GaAs/Ga0.62In0.38As0.22P0.78, Ga0.79In0.21As0.59P0.41/Ga0.51In0.49P, and Ga0.79In0.21As0.59P0.41/Ga0.62In0.38As0.22P0.78 QWIP’s. Through this analysis, the insignificance of spin split-off absorption in GaAs/AlxGa1-xAs QWIP’s is verified, as is the dual role of light-hole extended-state and spin split-off hole-extended-state absorption on the spectral shape of Ga1-xInxAsyP1-y QWIP’s. reprint
567.  Recent advances in III-Nitride materials, characterization and device applications
M. Razeghi, X. Zhang, P. Kung, A. Saxler, D. Walker, K.Y. Lim, and K.S. Kim
SPIE Conference: Solid State Crystals in Optoelectronics and Semiconductor Technology; Proceedings 3179-- October 7, 1996
High-quality AlN, GaN, AlGaN have been grown on sapphire substrate by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The x-ray rocking curve of AlN and GaN were 100 arcsecs and 30 arcsecs respectively with Pendelloesung oscillations, which are the best reported to date. GaN with high crystallinity simultaneously exhibited high optical and electrical quality. Photoluminescence linewidth of GaN at 77K was as low as 17 meV, which is the best reported to date. Si-doped GaN had a mobility higher than 300 cm²/V·s. GaN has been also successfully grown on LiGaO2 substrate with LP-MOCVD for the first time. AlGaN for the entire composition range has been grown. These layers exhibited the lowest x-ray FWHM reported to date. The excellent optical quality of these layers have been characterized by room temperature UV transmission and photoluminescence. N-type doping of AlGaN with Si has ben achieved up to 60 percent Al with mobility as high as 78 cm²/V·s. AlxGa1-xN/AlyGa1-yN superlattice with atomically sharp interface have been demonstrated. Optically-pumped stimulated emission in GaN:Ge and GaN:Si has been observed with threshold optical power density as low as 0.4 MW/cm². AlGaN photoconductors with cut-off wavelengths from 200 nm to 365 nm have been achieved for the first time. GaN p-n junction photovoltaic detector with very selective photoresponse have been demonstrated and theoretically modeled. Ti/AlN/Si metal-insulator- semiconductor capacitor with high capacitance-voltage performances at both low and high frequencies and low interface trap level density have been demonstrated for the first time in this material system. reprint
568.  Metalorganic chemical vapor deposition of monocrystalline GaN thin films on β-LiGaO2substrates
P. Kung, A. Saxler, X. Zhang, D. Walker, R. Lavado, and M. Razeghi
Applied Physics Letters 69 (14)-- September 30, 1996
We report the metalorganic chemical vapor deposition growth and characterization of monocrystalline GaN thin films on β-LiGaO2 substrates. The influence of the growth temperature on the crystal quality was studied. The structural, electrical, and optical properties of the films were assessed through scanning electron microscopy, x-ray diffraction, Hall measurements, optical transmission, photoluminescence. reprint
569.  III-V interband and intraband far-infrared detectors
M. Razeghi, C. Jelen, S. Slivken and J. Hoff
-- September 23, 1996
570.  Photoluminescence study of InAsSb/InAsSbP heterostructures grown by low-pressure metalorganic chemical vapor deposition
S. Kim, M. Erdtmann, D. Wu, E. Kaas, H. Yi, J. Diaz, and M. Razeghi
Applied Physics Letters 69 (11)-- September 9, 1996
Photoluminescence has been measured for double‐ and separate‐confinement InAsSb/InAsSbP heterostructures grown by low‐pressure metalorganic vapor deposition. A measurement of the integrated luminescence intensity at the temperature range of 77–300 K shows that over a wide range of excitation level (1–5×10² W/cm²) the radiative transitions are the dominant. mechanism below T∼170 K. Auger recombination coefficient C=C0 exp(−Ea/kT) with C0≊5×10−27 cm6/s and Ea≊40 meV has been estimated. reprint
571.  Room Temperature Operation of InTlSb Infrared Photodetectors on GaAs
J.D. Kim, E. Michel, S. Park, J. Xu, S. Javadpour and M. Razeghi
Applied Physics Letters 69 (3)-- August 15, 1996
Long-wavelength InTlSb photodetectors operating at room temperature are reported. The photo- detectors were grown on (100) semi-insulating GaAs substrates by low-pressure metalorganic chemical vapor deposition. Photoresponse of InTlSb photodetectors is observed up to 11 µm at room temperature. The maximum responsivity of an In0.96Tl0.04Sb photodetector is about 6.64 V/W at 77 K, corresponding to a detectivity of about 7.64 × 108 cm·Hz½/W. The carrier lifetime in InTlSb photodetectors derived from the stationary photoconductivity is 10–50 ns at 77 K. reprint
572.  Observation of inversion layers at AlN-Si interfaces fabricated by metal organic chemical vapour deposition
X. Zhang, D. Walker, A. Saxler, P. Kung, J. Xu, and M. Razeghi
-- August 15, 1996
573.  Demonstration of an Electronic Grade Ti/AlN/Si Metal-Insulator-Semiconductor Capacitor
X. Zhang, D. Walker, A. Saxler, P. Kung, J. Xu, and M. Razeghi
-- August 1, 1996
574.  The Molecular Beam Epitaxial Growth of InSb on (111) GaAs
E. Michel, J. Kim, J. Xu, S. Javadpour, I. Ferguson, and M. Razeghi
Applied Physics Letters 69 (2)-- July 8, 1996
The molecular beam epitaxial growth of InSb on (111)B GaAs has been investigated. It was found that for a given Sb/In ratio, a higher growth temperature was required for the growth of InSb on (111)B GaAs compared to that on (001) GaAs. This difference has been attributed to the bonding characteristics of the (111)B and (001) surface. Once growth had been optimized, it was found that the material characteristics of (111)B InSb were almost identical to that of (001) InSb, i.e., independent of orientation. For example, the x-ray full width at half-maximum and 300 K mobility had the same absolute values for (111) InSb and (001)InSb and followed the same dependence with the sample thickness. Te was found to be a well-behaved n-type dopant for (111)B InSb. reprint
575.  Comparison of Gain and Threshold Current Density for InGaAsP/GaAs λ = 808 nm) Lasers with Different Quantum-Well Thickness
H.J. Yi, J. Diaz, I. Eliashevich, G. Lukas, S. Kim, D. Wu, M. Erdtmann, C. Jelen, S. Slivken, L.J. Wang, and M. Razeghi
Journal of Applied Physics 79 (11)-- July 1, 1996
We investigated the quantum‐size effects of quantum well (QW) on gain and threshold current density for InGaAsP/GaAs (λ=808 nm) laser diodes. In this work, a comparison is made of lasers with different QW thickness while keeping the optical confinement factors constant. We found that the threshold current density and differential efficiency were not affected by narrowing the QW thickness. The theoretical model taking into account the mixing of the valence bands and momentum relaxation for InGaAsP/GaAs lasers with spontaneous emission (optically pumped) measurement shows that the absence of difference between these structures can be attributed to the high relaxation rate. reprint

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