Center for Quantum Devices - Journal Articles and Conference Proceedings

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576.	Schottky MSM Photodetectors on GaN Films Grown on Sapphire by Lateral Epitaxial Overgrowth P. Kung, D. Walker, P. Sandvik, M. Hamilton, J. Diaz, I.H. Lee and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 We report the growth and characterization of Schottky based metal-semiconductor-metal ultraviolet photodetectors fabricated on lateral epitaxially overgrown GaN films. The lateral epitaxial overgrowth of GaN was carried out on basal plane sapphire substrates by low pressure metalorganic chemical vapor deposition and exhibited lateral growth rates more than 5 times as high as vertical growth rates. The spectral responsivity, the dependence on bias voltage, on incident optical power, and the time response of these photodetectors have been characterized. Two detector orientations were investigated: one with the interdigitated finger pattern parallel and the other perpendicular to the underlying SiO_x mask stripes. reprint
577.	Growth of InAsSb Alloys on GaAs and Si Substrates for Uncooled Infrared Photodetector Applications J.D. Kim, H. Mohseni, J.S. Wojkowski, J.J. Lee and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 In this paper, we report on the growth and characterization of InAsSb alloys on GaAs and Si substrates for uncooled infrared photodetector applications. The fabrication and characterization of photodetectors from the grown layers are also reported. The photovoltaic and photoconductive devices were grown on (100) GaAs and Si substrates, respectively, using molecular beam epitaxy (MBE). The composition of InAs>sub>1-xSb_x layers was 0.95 in both cases and cut-off wavelength of 7-8 μm has been obtained. At 300 K, the photovoltaic detectors on GaAs substrates resulted in a sharp cut-off wavelength of 7.5 μm with a peak responsivity as high as 0.32 V/W at 6.5 micrometer. For the photoconductive detectors on Si substrates, cut-off wavelength of 8 μm has been observed with a responsivity of 6.3x10^-2 V/W at 7 μm under an electric field of 420 V/m. reprint
578.	Demonstration of InAsSb/AlInSb Double Heterostructure Detectors for Room Temperature Operation in the 5–8 μm Wavelength Range J.S. Wojkowski, H. Mohseni, J.D. Kim, and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 We report the first demonstration of InAsSb/AlInSb double heterostructure detectors for room temperature operation. The structures were grown in a solid source molecular beam epitaxy reactor on semi-insulating GaAs substrate. The material was processed to 400x400 micrometer mesas using standard photolithography, etching, and metallization techniques. No optical immersion or surface passivation was used. The photovoltaic detectors showed a cutoff wavelength at 8 micrometer at 300 K. The devices showed a high quantum efficiency of 40% at 7 μm at room temperature. A responsivity of 300 mA/W was measured at 7 μm under a reverse bias of 0.25 V at 300 K resulting in a Johnson noise limited detectivity of 2x10⁸ cm·Hz^½/W. reprint
579.	Characteristics of Self-Assembled InGaAs/InGaP Quantum Dot Mid-Infrared Photoconductive Detectors Grown by Low Pressure MOCVD S. Kim, M. Erdtmann, and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 We report the first self-assembled InGaAs/InGaP quantum dot intersubband infrared photoconductive detectors (QDIPs) grown on semi-insulating GaAs substrate by low pressure metal organic chemical vapor deposition (MOCVD). The InGaAs quantum dots were constructed on an InGaP matrix as self assembling in Stranski-Krastanow growth mode in optimum growth conditions. The detector structure was prepared for single layer and multi-stacked quantum dots for active region. Normal incident photoconductive response was observed at a peak wavelength of 5.5 μm with a high responsivity of 130 mA/W, and a detectivity of 4.74 X 10⁷ cm·Hz^½/W at 77 K for multi-stack QDIP. Low temperature photoresponse of the single quantum dot photodetector was characterized. Peak response was obtained between 16 K and 60 K. The detailed dark current noise measurements were carried on single and multistack quantum dot infrared detectors. High photoconductive gain as 7.6 x 10³ biased at 0.5 V results in increasing the intersubband carrier relaxation time as two order of magnitude compared quantum well infrared photodetectors. reprint
580.	Internal Stress Around Micropipes in 6H-SiC Substrates H. Ohsato, T. Kato, T. Okuda and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 6H-SiC single crystals are expected to be suitable substrates for thin film growth of the wide bandgap semiconductor (GaN, because it has a small lattice mismatch with GaN. Moreover, SiC single crystals are also expected for high-power and high- temperature electric applications because of its wide band gap, high breakdown voltage, high thermal conductivity and high temperature stability. Single crystals with large size used for electronic devices can be grown on seed crystals only by the modified Lely method based on sublimation deposition. But, single crystals have serious defects so called micropipes. These micropipes penetrate almost along the [001] direction. The internal strain around micropipes was investigated using the polarizing optical microscope for the purpose of clarifying the formation mechanisms and decreasing the amount of micropipes. A special interference figure was found around a micropipe under the crossed polars on the polarizing microscope. In this work, the special interference figure around micropipes due to internal stress was explained, and the magnitude and distribution of the stress was measured by means of photoelasticity and the mapping of Raman spectra. reprint
581.	Lateral epitaxial overgrowth of GaN films on sapphire and silicon substrates P. Kung, D. Walker, M. Hamilton, J. Diaz, and M. Razeghi Applied Physics Letters 74 (4)-- January 25, 1999 We report the lateral epitaxial overgrowth of GaN films on (00.1) Al₂O₃ and (111) Si substrates by metalorganic chemical vapor deposition. The lateral epitaxial overgrowth 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 lateral epitaxial overgrown films. Lateral growth rates more than five times as high as vertical growth rates were achieved for both lateral epitaxial overgrowths of GaN on sapphire and silicon substrates. reprint
582.	Relaxation kinetics in quantum cascade laser S. Slivken, V. Litvinov, M. Razeghi, and J.R. Meyer Journal of Applied Physics 85 (2)-- January 15, 1999 Relaxation kinetics in a quantum cascade intersubband laser are investigated. Distribution functions and gain spectra of a three-subband double-quantum-well active region are obtained as a function of temperature and injection current. The potentially important role of the nonequilibrium phonons at lasing threshold is shown and discussed in details. It is shown that the threshold current is strongly dependent of the power dissipated in the active region in steady state. The numerical calculations for an 8.5 μm laser illustrate the general issues of relaxation kinetics in quantum cascade lasers. Temperature dependence of the threshold current is obtained in a good agreement with the experiments. reprint
583.	High Temperature Continuous Wave Operation of ~8 μm Quantum Cascade Lasers S. Slivken, A. Matlis, C. Jelen, A. Rybaltowski, J. Diaz, and M. Razeghi Applied Physics Letters 74 (2)-- January 11, 1999 We report single-mode continuous-wave operation of a λ∼8 μm quantum cascade laser at 140 K. The threshold current density is 4.2 kA/cm² at 300 K in pulsed mode and 2.5 kA/cm² at 140 K in continuous wave for 2 mm long index-guided laser cavities of 20 μm width. Wide stripe (W ∼ 100 μm), index-guided lasers from the same wafer in pulsed operation demonstrate an average T₀ of 210 K with other wafers demonstrating a T₀ as high as 290 K for temperatures from 80 to 300 K. This improvement in high-temperature performance is a direct result of three factors: excellent material quality, a low-loss waveguide design, and a low-leakage index-guided laser geometry. reprint
584.	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
585.	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
586.	Current Status and Future Trends of Infrared Detectors M. Razeghi -- December 1, 1998
587.	Recent development in Sb-based MWIR interband laser diodes D. Wu and M. Razeghi -- December 1, 1998
588.	Relaxation kinetics in mid-infrared quantum cascade lasers S. Slivken, V.I. Litvinov, M. Razeghi, and J.R. Meyer -- December 1, 1998
589.	Investigation of InAsSb Infrared Photodetectors for Near Room Temperature Operation J.D. Kim and M. Razeghi -- December 1, 1998
590.	Low Threshold Quantum Cascade Lasers Grown by GSMBE M. Razeghi, S. Slivken, A. Matlis, A. Rybaltowski, C. Jelen, and J. Diaz -- December 1, 1998
591.	Development of High-performance III-Nitride-based Semiconductor Devices M. Razeghi, P. Kung, D. Walker, M. Hamilton, and P. Sandvik -- November 6, 1998
592.	Growth and Characterization of InAs/GaSb Type-II Superlattice for 8–12 μm Room Temperature Detectors H. Mohseni and M. Razeghi -- November 5, 1998
593.	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
594.	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
595.	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
596.	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
597.	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· Hz^½/W at 77 K. reprint
598.	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·Hz^½/W. The carrier lifetime derived from the voltage dependent responsivity measurements was about 0.7 ns. reprint
599.	Noise performance of InGaAs/InP quantum well infrared photodetectors C. Jelen, S. Slivken, T. David, M. Razeghi and G. J. Brown -- July 7, 1998
600.	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

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