Center for Quantum Devices - Journal Articles and Conference Proceedings

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601.	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
602.	Uncooled long-wavelength infrared photodetectors using narrow bandgap semiconductors M. Razeghi, J. Wojkowski, J.D. Kim, H. Mohseni and J.J. Lee Symposium on Compound Semiconductors, Nara, Japan; Proceedings-- October 12, 1998
603.	InGaAlAs/InP Quantum Well Infrared Photodetectors for 8-20 μm Wavelengths C. Jelen, S. Slivken, V. Guzman, M. Razeghi, and G. Brown IEEE Journal of Quantum Electronics 34 (10)-- October 1, 1998
604.	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
605.	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
606.	Noise performance of InGaAs/InP quantum well infrared photodetectors C. Jelen, S. Slivken, T. David, M. Razeghi and G. J. Brown IEEE Journal of Quantum Electronics 34 (7)-- July 7, 1998
607.	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
608.	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
609.	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
610.	Narrow gap semiconductor photodiodes A. Rogaski and M. Razeghi SPIE Conference, San Jose, CA, -- January 28, 1998
611.	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. Al_xGa_1-xN is a promising material system for such devices. Al_xGa_1-xN materials are wide bandgap semiconductors, with a direct bandgap whose corresponding wavelength can be continuously tuned from 200 to 365 nm. Al_xGa_1-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 Al_xGa_1-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
612.	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·Hz^½/W at 1.2 V bias were measured for the InGaAs/InP QWIPs at T = 80K. reprint
613.	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·Hz^½/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
614.	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
615.	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 Physics of Semiconductor Devices, Vol. 1, V. Kumar and S.K. Agarwal eds.,Narosa Publishing House, New Delhi, India,-- January 1, 1998
616.	Infrared Photodetectors and Imaging Arrays Using Advanced III-V Materials M. Razeghi Physics of Semiconductor Devices, Vol. 2 (V. Kumar and S.K. Agarwal eds.), Narosa Publishing House, New Delhi, India-- January 1, 1998
617.	GaInN/GaN Multi-Quantum Well Laser Diodes Grown by Low-Pressure Metalorganic Chemical Vapor Deposition P. Kung, A. Saxler, D. Walker, A. Rybaltowski, X. Zhang, J. Diaz, and M. Razeghi MRS Internet Journal of Nitride Semiconductor Research 3 (1)-- January 1, 1998 We report the growth, fabrication and characterization of GaInN/GaN multi-quantum well lasers grown on (00·1) sapphire substrates by low pressure metalorganic chemical vapor deposition. The threshold current density of a 1800 µm long cavity length laser was 1.4 kA/cm² with a threshold voltage of 25 V. These lasers exhibited series resistances of 13 and 14 Ω at 300 and 79 K, respectively. reprint
618.	Simultaneous growth of two differently oriented GaN epilayers on (11.0) sapphire (II) a growth model of (00.1) and (10.0) GaN T. Kato, P. Kung, A. Saxler, C.J. Sun, H. Ohsato, M. Razeghi and T. Okuda Journal of Crystal Growth 183-- January 1, 1998
619.	Recent advances in Sb-based materials for uncooled infrared photodetectors E. Michel and M. Razeghi Opto-Electronics Review 6 (1)-- January 1, 1998
620.	Exploration of InSbBi for uncooled long-wavelength infrared photodetectors J.J. Lee and M. Razeghi Opto-Electronics Review 6 (1)-- January 1, 1998
621.	High-Power Al-free InGaAsP/GaAs Near-Infrared Semiconductor Lasers M. Razeghi and H. Yi Opto-Electronics Review 6 (2)-- January 1, 1998
622.	GaN-Based Laser Diodes Manijeh Razeghi International Journal of High Speed Electronics and Systems (IJHSES), Volume: 9, Issue: 4, pp. 1007-1080 (1998)-- January 1, 1998 We discuss optical properties of III-Nitride materials and structures. These properties are critical for the development of III-Nitride-based light-emitting diodes and laser diodes. Minority carrier diffusion length in GaN has been determined to be ~0.1 μm. The properties of lasing in GaN have been studied using optical pumping. The red shift of emission peak observed in stimulated emission of GaN has been modeled and attributed to many-body interactions at high excitation. The correlation of photoluminescence and optical pumping has shown that band-to-band, or shallow donor-related bandtail to valence band transition is the necessary mechanism of lasing in GaN. This work showed that the thermal instability of InGaN at growth temperature is of main concern in the fabrication of InGaN-based MQW laser diode structures. Photoluminescence has shown that the InGaN composition is very sensitive to the growth temperature. Therefore InGaN growth temperature should be strictly controlled during InGaN-based MQW growth. This work discovered that proper annealing of Si-doping of InGaN/GaN MQW structures that are properly annealed could reduce the lasing threshold and improve the slope efficiency. Over-annealing of these MQWs can lead to thermal degradation of the active layer. Si-doping in over-annealed MQW structure further degrades its quality. The degradation has been attributed to the increase of defects and/or nonuniform local potential formation. P-type doping on the top of InGaN/GaN could also lead to the formation of compensation layer which also degrades laser diode performances. Optical confinement and carrier confinement in InGaN-based laser diode structures are evaluated for optimum laser diode design. The state-of-the-art and fundamental issues of InGaN-based light-emitting diodes and laser diodes are discussed.
623.	InP-based Multi-Spectral Quantum Well Infrared Photodetectors C. Jelen and M. Razeghi International Semiconductor Device Research Symposium (ISDRS 97), Charlottesville, VA; Proceedings-- December 11, 1997
624.	Mid-Infrared Quantum Cascade Lasers Grown by Gas-Source Molecular Beam Epitaxy S. Slivken and M. Razeghi International Semiconductor Device Research Symposium (ISDRS 97), Charlottesville, VA; Proceedings-- December 11, 1997
625.	Comparison of Trimethylgallium and Triethylgallium for the Growth of GaN A. Saxler, D. Walker, P. Kung, X. Zhang, M. Razeghi, J. Solomon, W. Mitchel, and H.R. Vydyanath Applied Physics Letters 71 (22)-- December 1, 1997 GaN films grown by low-pressure metalorganic chemical vapor deposition using trimethylgallium and triethylgallium as gallium precursors are compared. The films were characterized by x-ray diffraction, Hall effect, photoluminescence, secondary ion mass spectroscopy, and etch pit density measurements. GaN layers grown using triethylgallium exhibited superior electrical and optical properties and a lower carbon impurity concentration. reprint

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