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501.  Band-gap narrowing and potential fluctuation in Si-doped GaN
I.H. Lee, J.J. Lee, P. Kung, F.J. Sanchez, and M. Razeghi
Applied Physics Letters 74 (1)-- January 4, 1999
We investigate the optical properties of two sets of Si-doped GaN epitaxial layers with different degree of compensation. The electron concentration dependence of the band-gap energy measured by photoluminescence is interpreted as band-gap narrowing effect and evaluated by a simple relation. The photoluminescence peak positions of heavily compensated samples are shifted downward with respect to those of moderately compensated samples, and the down shift becomes larger at higher electron density. Based on analysis of photoluminescence spectra, these prominent behaviors are accounted for by band-edge potential fluctuation associated with inhomogeneous residual impurities. reprint
502.  Interface-induced Suppression of the Auger Recombination in Type-II InAs/GaSb Superlattices
H. Mohseni, V.I. Litvinov and M. Razeghi
Physical Review B 58 (23)-- December 15, 1998
The temperature dependence of the nonequilibrium carriers lifetime has been deduced from the measurement of the photocurrent response in InAs/GaSb superlattices. Based on the temperature dependence of the responsivity and modeling of the transport parameters we have found that the carrier lifetime weakly depends on temperature in the high-temperature region. This indicates the temperature dependence of the Auger recombination rate with no threshold that differs it from that in the bulk material and can be attributed to the interface-induced suppression of the Auger recombination in thin quantum wells. reprint
503.  Current Status and Future Trends of Infrared Detectors
M. Razeghi
-- December 1, 1998
504.  Recent development in Sb-based MWIR interband laser diodes
D. Wu and M. Razeghi
-- December 1, 1998
505.  Relaxation kinetics in mid-infrared quantum cascade lasers
S. Slivken, V.I. Litvinov, M. Razeghi, and J.R. Meyer
-- December 1, 1998
506.  Investigation of InAsSb Infrared Photodetectors for Near Room Temperature Operation
J.D. Kim and M. Razeghi
-- December 1, 1998
507.  Low Threshold Quantum Cascade Lasers Grown by GSMBE
M. Razeghi, S. Slivken, A. Matlis, A. Rybaltowski, C. Jelen, and J. Diaz
-- December 1, 1998
508.  Development of High-performance III-Nitride-based Semiconductor Devices
M. Razeghi, P. Kung, D. Walker, M. Hamilton, and P. Sandvik
-- November 6, 1998
509.  Growth and Characterization of InAs/GaSb Type-II Superlattice for 8–12 μm Room Temperature Detectors
H. Mohseni and M. Razeghi
-- November 5, 1998
510.  Growth and Characterization of Self-Assembled InGaAs/InGaP Quantum Dots for Mid-Infrared Photoconductive Detector by LP-MOCVD
S. Kim and M. Razeghi
-- November 5, 1998
511.  High quality LEO growth and characterization of GaN films on Al2O3 and Si substrates
M. Razeghi, P. Kung, D. Walker, M. Hamilton, and J. Diaz
SPIE International Conference on Solid State Crystals, Zakopane, Poland; Proceedings 3725-- October 12, 1998
We report the lateral epitaxial overgrowth (LEO) of GaN films on (00.1) Al2O3 and (111) Si substrates by metalorganic chemical vapor deposition. The LEO on Si substrates was possible after achieving quasi monocrystalline GaN template films on (111) Si substrates. X-ray diffraction, photoluminescence, scanning electron microscopy and atomic force microscopy were used to assess the quality of the LEO films. Lateral growth rates more than 5 times as high as vertical growth rates were achieved for both LEO growths of GaN on sapphire and silicon substrates. reprint
512.  Uncooled long-wavelength infrared photodetectors using narrow bandgap semiconductors
M. Razeghi, J. Wojkowski, J.D. Kim, H. Mohseni and J.J. Lee
-- October 12, 1998
513.  InGaAlAs/InP Quantum Well Infrared Photodetectors for 8-20 μm Wavelengths
C. Jelen, S. Slivken, V. Guzman, M. Razeghi, and G. Brown
-- October 1, 1998
514.  Growth and characterization of InGaAs/InGaP quantum dots for mid-infrared photoconductive detector
S. Kim, H. Mohseni, M. Erdtmann, E. Michel, C. Jelen and M. Razeghi
Applied Physics Letters 73 (7)-- August 17, 1998
We report InGaAs quantum dot intersubband infrared photodetectors grown by low-pressure metalorganic chemical vapor deposition on semi-insulating GaAs substrates. The optimum growth conditions were studied to obtain uniform InGaAs quantum dots constructed in an InGaP matrix. Normal incidence photoconductivity was observed at a peak wavelength of 5.5 μm with a high responsivity of 130 mA/W and a detectivity of 4.74×107  cm· Hz½/W at 77 K. reprint
515.  Room temperature operation of 8-12 μm InSbBi infrared photodetectors on GaAs substrates
J.J. Lee, J.D. Kim, and M. Razeghi
Applied Physics Letters 73 (5)-- August 3, 1998
We report the room temperature operation of 8–12 μm InSbBi long-wavelength infrared photodetectors. The InSbBi/InSb heterostructures were grown on semi-insulating GaAs (001) substrates by low pressure metalorganic chemical vapor deposition. The voltage responsivity at 10.6 μm was about 1.9 mV/W at room temperature and the corresponding Johnson noise limited detectivity was estimated to be about 1.2×106 cm·Hz½/W. The carrier lifetime derived from the voltage dependent responsivity measurements was about 0.7 ns. reprint
516.  Noise performance of InGaAs/InP quantum well infrared photodetectors
C. Jelen, S. Slivken, T. David, M. Razeghi and G. J. Brown
-- July 7, 1998
517.  Solar blind GaN p-i-n photodiodes
D. Walker, A. Saxler, P. Kung, X. Zhang, M. Hamilton, J. Diaz and M. Razeghi
Applied Physics Letters 72 (25)-- June 22, 1998
We present the growth and characterization of GaN p-i-n photodiodes with a very high degree of visible blindness. The thin films were grown by low-pressure metalorganic chemical vapor deposition. The room-temperature spectral response shows a high responsivity of 0.15 A/W up until 365 nm, above which the response decreases by six orders of magnitude. Current/voltage measurements supply us with a zero bias resistance of 1011  Ω. Lastly, the temporal response shows a rise and fall time of 2.5 μs measured at zero bias. This response time is limited by the measurement circuit. reprint
518.  8.5 μm Room Temperature Quantum Cascade Lasers Grown by Gas-Source Molecular Beam Epitaxy
S. Slivken and M. Razeghi
SPIE Conference, San Jose, CA, -- January 28, 1998
We report room-temperature pulsed-mode operation of 8.5 μm quantum cascade lasers grown by gas-source molecular beam epitaxy. The theory necessary to understand the operation of the laser is presented and current problems are analyzed. Very good agreement is shown to exist between theoretical and experimental emission wavelengths. The high- temperature operation is achieved with 1 μs pulses at a repetition rate of 200 Hz. Peak output power in these conditions is in excess of 700 mW per 2 facets at 79 K and 25 mW at 300 K. Threshold current as a function of temperature shows an exponential dependence with T0 equals 188 K for a 1.5 mm cavity. reprint
519.  Continuous-wave room-temperature operation of InGaN/GaN multiquantum well lasers grown by low-pressure metalorganic chemical vapor deposition
M. Razeghi, A. Saxler, P. Kung, D. Walker, X. Zhang, A. Rybaltowski, Y. Xiao, H.J. Yi and J. Diaz
SPIE Conference, San Jose, CA, Vol. 3284, pp. 113-- January 28, 1998
Continuous-wave (CW) room temperature operation of InGaN/GaN multi-quantum well (MQW) lasers is reported. Far-field beam divergence as narrow as 13 degrees and 20 degrees for parallel and perpendicular directions to epilayer planes were measured, respectively. The MQW lasers showed strong beam polarization anisotropy as consistent with QW laser gain theory. Dependencies of threshold current on cavity-length and temperature are also consistent with conventional laser theory. No significant degradation in laser characteristics was observed during lifetime testing for over 140 hours of CW room temperature operation. reprint
520.  Narrow gap semiconductor photodiodes
A. Rogaski and M. Razeghi
-- January 28, 1998
521.  GaN p-i-n photodiodes with high visible-to-ultraviolet rejection ratio
P. Kung, X. Zhang, D. Walker, A. Saxler, and M. Razeghi
SPIE Conference, San Jose, CA, -- January 28, 1998
UV photodetectors are critical components in many applications, including UV astronomy, flame sensors, early missile threat warning and space-to-space communications. Because of the presence of strong IR radiation in these situations, the photodetectors have to be solar blind, i.e. able to detect UV radiation while not being sensitive to IR. AlxGa1-xN is a promising material system for such devices. AlxGa1-xN materials are wide bandgap semiconductors, with a direct bandgap whose corresponding wavelength can be continuously tuned from 200 to 365 nm. AlxGa1-xN materials are thus insensitive to visible and IR radiation whose wavelengths are higher than 365 nm. We have already reported the fabrication and characterization of AlxGa1-xN-based photoconductors with a cut-off wavelength tunable from 200 to 365 nm by adjusting the ternary alloy composition. Here, we present the growth and characterization of GaN p-i- n photodiodes which exhibit a visible-to-UV rejection ratio of 6 orders or magnitude. The thin films were grown by low pressure metalorganic chemical vapor deposition. Square mesa structures were fabricated using dry etching, followed by contact metallization. The spectral response, rejection ratio and transient response of these photodiodes is reported. reprint
522.  Responsivity and Noise Performance of InGaAs/InP Quantum Well Infrared Photodetectors
C. Jelen, S. Slivken, T. David, G. Brown, and M. Razeghi
SPIE Conference, San Jose, CA, -- January 28, 1998
Dark current nose measurements were carried out between 10 and 104 Hz at T = 80K on two InGaAs/InP quantum well IR photo detectors (QWIPs) designed for 8 μm IR detection. Using the measured noise data, we have calculated the thermal generation rate, bias-dependent gain, electron trapping probability, and electron diffusion length. The calculated thermal generation rate is similar to AlGaAs/GaAs QWIPs with similar peak wavelengths, but the gain is 50X larger, indicating improved transport and carrier lifetime are obtained in the binary InP barriers. As a result, a large responsivity of 7.5 A/W at 5V bias and detectivity of 5 X 1011 cm·Hz½/W at 1.2 V bias were measured for the InGaAs/InP QWIPs at T = 80K. reprint
523.  Growth and characterization of InAs/GaSb Type-II superlattices for long-wavelength infrared detectors
H. Mohseni, E. Michel, M. Razeghi, W. Mitchel, and G. Brown
SPIE Conference, San Jose, CA, -- January 28, 1998
We report the molecular beam epitaxial growth and characterization of InAs/GaSb superlattices grown on semi- insulating GaAs substrate for long wavelength IR detectors. Photoconductive detectors fabricated from the superlattices showed 80% cut-off at 11.6 μm and peak responsivity of 6.5 V/W with Johnson noise limited detectivity of 2.36 x 109 cm·Hz½/W at 10.7 μm at 78 K. The responsivity decreases at higher temperatures with a T-2 behavior rather than exponential decay, and at room temperature the responsivity is about 660 mV/W at 11 μm. Lower Auger recombination rate in this system provides comparable detectivity to the best HgCdTe detectors at 300K. Higher uniformity over large areas, simpler growth and the possibility of having read-out circuits in the same GaAs chip are the advantages of this system over HgCdTe detectors for near room temperature operation. reprint
524.  Electrical Transport Properties of Highly Doped N-type GaN Epilayers
H.J. Lee, M.G. Cheong, E.K. Suh, and M. Razeghi
SPIE Conference, San Jose, CA, -- January 28, 1998
Temperature-dependent Hall-effects in MOCVD-grown Si-doped GaN epilayers were measured as a function of temperature in the range 10-800 K. The results were satisfactorily analyzed in terms of a two-band model including the (Gamma) and impurity bands at lower temperatures than room. The (Gamma) band electrons are dominant only high temperatures. The ionized impurity scattering is the most important in the (Gamma) band except at very high temperatures. reprint
525.  New Developments in III-Nitride Material and Device Applications
M. Razeghi, A. Saxler, P. Kung, D. Walker, X. Zhang, K.S. Kim, H.R. Vydyanath, J. Solomon, M. Ahoujja, and W.C. Mitchel
-- January 1, 1998

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