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601.  MOCVD Growth of Ga1-xInxAsyP1-y-GaAs Quantum Structures
M. Razeghi, J. Hoff, M. Erdtmann, S. Kim, D. Wu, E. Kaas, C. Jelen, S. Slivken, I. Eliashevich, J. Diaz, E. Bigan, G.J. Brown, S. Javadpour
-- January 1, 1996
602.  Semiconductor ultraviolet photodetectors
A. Rogalski and M. Razeghi
-- January 1, 1996
603.  Kinetics of photoconductivity in n-type GaN photodetector
P. Kung, X. Zhang, D. Walker, A. Saxler, J. Piotrowski, A. Rogalski, and M. Razeghi
Applied Physics Letters 67 (25)-- December 18, 1995
High-quality ultraviolet photoconductive detectors have been fabricated using GaN layers grown by low-pressure metalorganic chemical vapor deposition on (11⋅0) sapphire substrates. The spectral responsivity remained nearly constant for wavelengths from 200 to 365 nm and dropped sharply by almost three orders of magnitude for wavelengths longer than 365 nm. The kinetics of the photoconductivity have been studied by the measurements of the frequency‐dependent photoresponse and photoconductivity decay. Strongly sublinear response and excitation‐dependent response time have been observed even at relatively low excitation levels. This can be attributed to redistribution of the charge carriers with increased excitation level. reprint
604.  MOVPE Growth of High Electron Mobility AlGaN/GaN Heterostructures
J.M. Redwing, J.S. Flynn, M.A. Tischler, W. Mitchel, and A. Saxler
-- November 27, 1995
605.  The Microstructural Study of Aluminum Nitride Thin Films: Epitaxy on the Two Orientations of Sapphire and Texturing on Si
K. Dovidenko, S. Oktyabrsky, J. Narayan, and M. Razeghi
-- November 27, 1995
606.  Spectral response on GaN p-n junction photovoltaic structures
D. Walker, X. Zhang, P. Kung, A. Saxler, J. Xu and M. Razeghi
-- November 27, 1995
607.  Growth of GaN without yellow luminescence
X. Zhang, P. Kung, D. Walker, A. Saxler, and M. Razeghi
-- November 27, 1995
608.  8-13 μm InAsSb heterojunction photodiode operating at near room temperature
J.D. Kim, S. Kim, D. Wu, J. Wojkowski, J. Xu, J. Piotrowski, E. Bigan, and M. Razeghi
Applied Physics Letters 67 (18)-- October 30, 1995
p+-InSb/π-InAs1−xSbx/n+-InSb heterojunction photodiodes operating at near room temperature in the 8–13 μm region of infrared (IR) spectrum are reported. A room‐temperature photovoltaic response of up to 13 μm has been observed at 300 K with an x≊0.85 sample. The voltage responsivity‐area product of 3×10−5 V· cm²/W has been obtained at 300 K for the λ=10.6 μm optimized device. This was close to the theoretical limit set by the Auger mechanism, with a detectivity at room temperature of ≊1.5×108 cm ·Hz½/W. reprint
609.  Photovoltaic effects in GaN structures with p-n junction
X. Zhang, P. Kung, D. Walker, J. Piotrowski, A. Rogalski, A. Saxler, and M. Razeghi
Applied Physics Letters 67 (14)-- October 2, 1995
Large-area GaN photovoltaic structures with p-n junctions have been fabricated using atmospheric pressure metalorganic chemical vapor deposition. The photovoltaic devices typically exhibit selective spectral characteristics with two narrow peaks of opposite polarity. This can be related to p-n junction connected back‐to‐back with a Schottky barrier. The shape of the spectral characteristic is dependent on the thickness of the n- and p-type regions. The diffusion length of holes in the n-type GaN region, estimated by theoretical modeling of the spectral response shape, was about 0.1 μm. reprint
610.  Growth of AlxGa1-xN:Ge on sapphire and silicon substrates
X. Zhang, P. Kung, A. Saxler, D. Walker, T.C. Wang, and M. Razeghi
Applied Physics Letters 67 (12)-- September 18, 1995
AlxGa1–xN were grown on (00.1) sapphire and (111) silicon substrates in the whole composition range (0 <= x <= 1). The high optical quality of the epilayers was assessed by room-temperature optical absorption and photoluminescence measurements. Layers with higher Al composition are more resistive. Resistive AlxGa1–xN epilayers were successfully doped with Ge and free-electron concentration as high as 3 × 1019 cm–3 was achieved. reprint
611.  Epitaxial Growth of Aluminum Nitride on Sapphire and Silicon
K. Dovidenko, S. Oktyabrsky, J. Narayan, and M. Razeghi
-- September 1, 1995
612.  InGaAsP-based High Power Laser Diodes
M. Razeghi
-- August 1, 1995
613.  p-doped GaAs/Ga0.51In0.49P quantum well intersub-band photodetectors
J. Hoff, X. He, M. Erdtmann, E. Bigan, M. Razeghi, and G.J. Brown
Journal of Applied Physics 78 (3)-- August 1, 1995
Lattice‐matched p-doped GaAs–Ga0.51In0.49P quantum well intersub‐band photodetectors with three different well widths have been grown on GaAs substrates by metal‐organic chemical‐vapor deposition and fabricated into mesa structures. The photoresponse cutoff wavelength varies between 3.5 and 5.5 μm by decreasing the well width from 50 down to 25 Å. Dark current measurements as a function of temperature reveal activation energies for thermionic emission that closely correspond to measured cutoff wavelengths. Experimental results are in reasonable agreement with Kronig–Penney calculations. reprint
614.  Background Limited Performance in p-doped GaAs/Ga[0.71]In[0.29]As[0.39]P[0.61] Quantum Well Infrared Photodetectors
J. Hoff, S. Kim, M. Erdtmann, R. Williams, J. Piotrowski, E. Bigan, M. Razeghi and G. Brown
Applied Physics Letters 67 (1)-- July 3, 1995
Background limited infrared photodetection has been achieved up to 100 K at normal incidence with p-type GaAs/Ga0.71In0.29As0.39P0.61 quantum well intersubband photodetectors grown by low-pressure metalorganic chemical vapor deposition. Photoresponse covers the wavelength range from 2.5 μm up to 7 μm. The device shows photovoltaic response, the cutoff wavelength increases slightly with bias, and the responsivity increases nonlinearly with bias. These effects are attributed to an asymmetric quantum well profile. reprint
615.  Optimized structure for InGaAsP/GaAs 808nm high power lasers
H. Yi, J. Diaz, L.J. Wang, I. Eliashevich, S. Kim, R. Williams, M. Erdtmann, X. He, E. Kolev and M. Razeghi
Applied Physics Letters 66 (24)-- June 12, 1995
The optimized structure for the InGaAsP/GaAs quaternary material lasers (λ=0.808 μm) is investigated for the most efficient high‐power operation through an experiment and theoretical study. A comparative study is performed of threshold current density Jth and differential efficiency ηd dependence on cavity length (L) for two different laser structures with different active layer thickness (150 and 300 Å) as well as for laser structures with different multiple quantum well structures. A theoretical model with a more accurate formulation for minority leakage phenomenon provides explanation for the experimental results and sets general optimization rules for other lasers with similar restrictions on the band gap and refractive index difference between the active layer and the cladding layers. reprint
616.  Reliability of Aluminum-Free 808 nm High-Power Laser Diodes with Uncoated Mirrors
I. Eliashevich, J. Diaz, H. Yi, L. Wang, and M. Razeghi
Applied Physics Letters 66 (23)-- June 5, 1995
The reliability of uncoated InGaAsP/GaAs high‐power diode lasers emitting at 808 nm wavelength has been studied. 47 W of quasicontinuous wave output power (pulse width 200 μs, frequency 20 Hz) have been obtained from a 1 cm wide laser bar. A single‐stripe diode without mirror coating has been life tested at 40 °C for emitting power of 800 mW continuous wave (cw) and showed no noticeable degradation and no change of the lasing wavelength after 6000 h of operation. reprint
617.  High quality AlN and GaN epilayers grown on (00*1) sapphire, (100) and (111) silicon substrates
P. Kung, A. Saxler, X. Zhang, D. Walker, T.C. Wang, I. Ferguson, and M. Razeghi
Applied Physics Letters 66 (22)-- May 29, 1995
The growth of high quality AlN and GaN thin films on basal plane sapphire, (100), and (111) silicon substrates is reported using low pressure metalorganic chemical vapor deposition. X-ray rocking curve linewidths of about 100 and 30 arcsec were obtained for AlN and GaN on sapphire, respectively. Room‐temperature optical transmission and photoluminescence (of GaN) measurements confirmed the high quality of the films. The luminescence at 300 and 77 K of the GaN films grown on basal plane sapphire, (100), and (111) silicon was compared. reprint
618.  Photoluminescence study of GaN
X. Zhang, P. Kung, A. Saxler, D. Walker, T. Wang, and M. Razeghi
-- May 29, 1995
619.  High Power Aluminum-free InGaAsP/GaAs Pumping Diode Lasers
M. Razeghi, I. Eliashevich, J. Diaz, H.J. Yi, S. Kim, M. Erdtmann, D. Wu, and L.J. Wang
-- May 8, 1995
620.  Second harmonic generation in hexagonal silicon carbide
P.M. Lundquist, W.P. Lin, G.K. Wong, M. Razeghi, and J.B. Ketterson
Applied Physics Letters 66 (15)-- April 10, 1995
We report optical second harmonic generation measurements in single crystal α-SiC of polytype 6H. The angular dependence of second harmonic intensity was consistent with two independent nonvanishing second order susceptibility components, as expected for a crystal with hexagonal symmetry. For the fundamental wavelength of 1.064 μm the magnitudes of the two components were determined to be χzzz(2)=±1.2×10−7 and χzxx(2)=∓1.2×10−8 esu. The corresponding linear electro‐optic coefficient computed from this value is rzzz=±100 pm/V. The wavelength dependence of the nonlinear susceptibility was examined for second harmonic wavelengths between the bandgap (400 nm) and the red (700 nm), and was found to be relatively uniform over this region. The refractory nature of this compound and its large nonlinear optical coefficients make it an attractive candidate for high power nonlinear optical waveguide applications. reprint
621.  Molecular Beam Epitaxial Growth of High Quality InSb for p-i-n Photodetectors
G. Singh, E. Michel, C. Jelen, S. Slivken, J. Xu, P. Bove, I. Ferguson, and M. Razeghi
Journal of Vacuum Science and Technology B, 13 (2)-- March 1, 1995
The InSb infrared photodetectors grown heteroepitaxially on Si substrates by molecular beam epitaxy (MBE) are reported. Excellent InSb material quality is obtained on 3-inch Si substrates (with a GaAs predeposition) as confirmed by structural, optical, and electrical analysis. InSb infrared photodetectors on Si substrates that can operate from 77 K to room temperature have been demonstrated. The peak voltage-responsitivity at 4 μm is about 1.0×103 V/W and the corresponding Johnson-noise-limited detectivity is calculated to be 2.8×1010 cm·Hz½/W. This is the first important stage in developing InSb detector arrays or monolithic focal plane arrays (FPAs) on silicon. The development of this technology could provide a challenge to traditional hybrid FPA's in the future. reprint
622.  Ultraviolet Detectors for AstroPhysics Present and Future
M. Ulmer, M. Razeghi, and E. Bigan
Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 239-- February 6, 1995
Astronomical instruments for the study of UV astronomy have been developed for NASA missions such as the Hubble Space Telescope. The systems that are `blind to the visible' (`solar-blind') yet sensitive to the UV that have been flown in satellites have detective efficiencies of about 10 to 20%, although typically electron bombardment charge coupled devices are higher at 30 - 40% and ordinary CCDs achieve 1 - 5%. Therefore, there is a large payoff still to be gained by further improvements in the performance of solar blind UV detectors. We provide a brief review of some aspects of UV astronomy, UV detector development, and possible technologies for the future. We suggest that a particularly promising future technology is one based on the ability of investigators to produce high quality films made of wide bandgap III-V semiconductors. reprint
623.  Improved performance of IR photodetectors with 3D gap engineering
J. Piotrowski and M. Razeghi
Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995
The ultimate signal-to-noise performance of the semiconductor photodetector is limited by the statistical fluctuations of the thermal generation and recombination rates in photodetector material. Cooling is an effective but impractical way of suppression of the thermal processes. The performance of uncooled detectors can be improved by minimizing the thermal generation and recombination rates and reducing the actual volume of photodetector. This can be realized in 3D heterostructure devices. In these devices, the incident radiation is absorbed in small regions of narrow gap semiconductor, buried in wide gap volume and supplied with wide gap electric contacts and radiation concentrators. The practical near room-temperature 1 - 12 μm IR heterostructure photodetectors are reported. The devices are based on variable gap Hg1-xCdxTe. The 3D heterostructures have been obtained by Isothermal Vapor Growth Epitaxy in a reusable growth system which enables in situ doping during growth with foreign impurities. Ion milling was extensively used in preparation of the devices. Monolithic optical immersion has been applied for further improvement of performance. The 3D heterostructure devices exhibit performance exceeding that of conventional photodetectors. reprint
624.  Investigation of 0.8 μm InGaAsP-GaAs laser diodes with Multiple Quantum Wells
J. Diaz, H. Yi, S. Kim, M. Erdtmann, L.J. Wang, I. Eliashevich, E. Bigan and M. Razeghi
Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995
In this paper, we studied the effects of the active region structure (one, two and three quantum wells with same total thickness) for high-power InGaAsP-GaAs separate confinement heterostructure lasers emitting at 0.8 μm wavelength. Experimental results for the lasers grown by low pressure metalorganic chemical vapor deposition show excellent agreement with the theoretical model. Total output power of 47 W from an uncoated 1 cm-wide laser bar was achieved in quasi-continuous wave operation reprint
625.  Molecular beam epitaxial growth of InSb p-i-n photodetectors on GaAs and Si
E. Michel, R. Peters, S. Slivken, C. Jelen, P. Bove, J. Xu, I. Ferguson, and M. Razeghi
Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995
High quality InSb has been grown by Molecular Beam Epitaxy and optimized using Reflection High Energy Electron Diffraction. A 4.8 micrometers InSb layer grown on GaAs at a growth temperature of 395 degree(s)C and a III/V incorporation ratio of 1:1.2 had an X-ray rocking curve FWHM of 158 arcsec and a Hall mobility of 92300 cm2V-1s-1 at 77 K, the best reported to date for InSb nucleated directly onto GaAs. InSb p-i-n structures of 5.8 micrometers grown under the same conditions demonstrated a X-ray Full Width at Half Maximum of 101 arcsec and 131 arcsec for GaAs and Si substrates, respectively, and exhibited excellent uniformity of +/- 3 arcsec over a 3' substrate. Prototype InSb p-i-n detectors on Si have been fabricated and have demonstrated photovoltaic response at 6.5 micrometers up to 200 K. These p-i-n detectors have also exhibited the highest D* for a device grown onto Si. reprint

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