Center for Quantum Devices - Most Downloaded Journal Articles

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1.	Review of high power frequency comb sources based on InP From MIR to THZ at CQD Manijeh Razeghi, Quanyong Lu, Donghai Wu, Steven Slivken Event: SPIE Optical Engineering + Applications, 2018, San Diego, California, United States-- September 14, 2018 ...[Visit Journal] We present the recent development of high performance compact frequency comb sources based on mid-infrared quantum cascade lasers. Significant performance improvements of our frequency combs with respect to the continuous wave power output, spectral bandwidth, and beatnote linewidth are achieved by systematic optimization of the device's active region, group velocity dispersion, and waveguide design. To date, we have demonstrated the most efficient, high power frequency comb operation from a free-running room temperature continuous wave (RT CW) dispersion engineered QCL at λ~5-9 μm. In terms of bandwidth, the comb covered a broad spectral range of 120 cm⁻¹ with a radio-frequency intermode beatnote spectral linewidth of 40 Hz and a total power output of 880 mW at 8 μm and 1 W at ~5.0 μm. The developing characteristics show the potential for fast detection of various gas molecules. Furthermore, THz comb sources based on difference frequency generation in a mid-IR QCL combs could be potentially developed. [reprint (PDF)]
1.	High-power laser diodes based on InGaAsP alloys M. Razeghi Nature, Vol.369, p.631-633-- June 23, 1994 ...[Visit Journal] HIGH-POWER, high-coherence solid-state lasers, based on dielectric materials such as ruby or Nd:YAG (yttrium aluminium garnet), have many civilian and military applications. The active media in these lasers are insulating, and must therefore be excited (or ‘pumped’) by optical, rather than electrical, means. Conventional gas-discharge lamps can be used as the pumping source, but semiconductor diode lasers are more efficient, as their wavelength can be tailored to match the absorption properties of the lasing material. Semiconducting AlGaAs alloys are widely used for this purpose, but oxidation of the aluminium and the spreading of defects during device operation limit the lifetime of the diodes3, and hence the reliability of the system as a whole. Aluminium-free InGaAsP compounds, on the other hand, do not have these lifetime-limiting properties. We report here the fabrication of high-power lasers based on InGaAsP (lattice-matched to GaAs substrates), which operate over the same wavelength range as conventional AlGaAs laser diodes and show significantly improved reliability. The other optical and electrical properties of these diodes are either comparable or superior to those of the AlGaAs system. [reprint (PDF)]
1.	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 ...[Visit Journal] 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 (PDF)]
1.	Material and design engineering of (Al)GaN for high-performance avalanche photodiodes and intersubband applications M. Razeghi and C. Bayram SPIE Proceedings, Dresden, Germany (May 4-6, 2009), Vol. 7366, p. 73661F-1-- May 20, 2009 ...[Visit Journal] Numerous applications in scientific, medical, and military areas demand robust, compact, sensitive, and fast ultraviolet (UV) detection. Our (Al)GaN photodiodes pose high avalanche gain and single-photon detection efficiency that can measure up to these requirements. Inherit advantage of back-illumination in our devices offers an easier integration and layout packaging via flip-chip hybridization for UV focal plane arrays that may find uses from space applications to hostile-agent detection. Thanks to the recent (Al)GaN material optimization, III-Nitrides, known to have fast carrier dynamics and short relaxation times, are employed in (Al)GaN based superlattices that absorb in near-infrared regime. In this work, we explain the origins of our high performance UV APDs, and employ our (Al)GaN material knowledge for intersubband applications. We also discuss the extension of this material engineering into the far infrared, and even the terahertz (THz) region. [reprint (PDF)]
1.	Demonstration of Planar Type-II Superlattice-Based Photodetectors Using Silicon Ion-Implantation Arash Dehzangi, Donghai Wu, Ryan McClintock, Jiakai Li, Alexander Jaud and Manijeh Razeghi Photonics 2020, 7(3), 68; https://doi.org/10.3390/photonics7030068-- September 3, 2020 ...[Visit Journal] In this letter, we report the demonstration of a pBn planar mid-wavelength infrared photodetectors based on type-II InAs/InAs1−xSbx superlattices, using silicon ion-implantation to isolate the devices. At 77 K the photodetectors exhibited peak responsivity of 0.76 A/W at 3.8 µm, corresponding to a quantum efficiency, without anti-reflection coating, of 21.5% under an applied bias of +40 mV with a 100% cut-off wavelength of 4.6 µm. With a dark current density of 5.21 × 10−6 A/cm2, under +40 mV applied bias and at 77 K, the photodetector exhibited a specific detectivity of 4.95 × 1011 cm·Hz1/2/W. [reprint (PDF)]
1.	Low Dark Current Deep UV AlGaN Photodetectors on AlN Substrate Lakshay Gautam, Junhee Lee, Gail Brown, Manijeh Razeghi IEEE Journal of Quantum Electronics, vol. 58, no. 3, pp. 1-5, June 2022, Art no. 4000205 ...[Visit Journal] We report high quality, low dark current, deep Ultraviolet AlGaN/AlN Photodetectors on AlN substrate. AlGaN based Photodetectors are grown and fabricated both on AlN and Sapphire substrates with the same epilayer structure. Subsequently, electrical characteristics of both photodetectors on AlN substrate and Sapphire are compared. A reduction of 4 orders of magnitude of dark current density is reported in UV detectors grown on AlN substrate with respect to Sapphire substrate. [reprint (PDF)]
1.	InTlSb alloys for infrared detection E. Bigan, Y.H. Choi, G. Labeyrie, and M. Razeghi Proceedings, SPIE Nonlinear Optics for High-Speed Electronics and Optical Frequency Conversion, Vol. 2145-- January 24, 1994 ...[Visit Journal] InTISb alloys have been grown by low-pressure metalorganic chemical vapor deposition, and characterized. Photoconductors exhibit a cutoff wavelength that can be tailored from 5.5 μm up to 9 μm by varying the thallium content. Experimental observations suggest that this can be further extended by increasing the thallium content. An InTISb photoconductor having a 9 μm cutoff wavelength exhibited a D* of 10⁹ cm·Hz^½·W^-1 at 7 μm operating wavelength. [reprint (PDF)]
1.	Uncooled InAs/GaSb Type-II infrared detectors grown on GaAs substrate for the 8–12 μm atmospheric window H. Mohseni, J. Wojkowski, M. Razeghi, G. Brown, and W. Mitchel IEEE Journal of Quantum Electronics 35 (7)-- July 1, 1999 ...[Visit Journal] The operation of uncooled InAs-GaSb superlattice photodiodes with a cutoff wavelength of λ_c=8 μm and a peak detectivity of 1.2×10⁸ cm·Hz^½/W at zero bias is demonstrated. The detectivity is similar to the best uncooled HgCdTe detectors and microbolometers. However, the R₀A product is more than two orders of magnitude higher than HgCdTe and the device is more than four orders of magnitude faster than microbolometers. These features combined with their low 1/f noise and high uniformity make these type-II photodiodes an excellent choice for uncooled high-speed IR imaging arrays [reprint (PDF)]
1.	Nickel oxide growth on Si (111), c-Al₂O₃ and FTO/glass by pulsed laser deposition V. E. Sandana ; D. J. Rogers ; F. Hosseini Teherani ; P. Bove ; R. McClintock ; M. Razeghi 03/07/2014-- March 7, 2014 ...[Visit Journal] NiO was grown on Si (111), c-Al₂O₃ and FTO/glass substrates by pulsed laser deposition (PLD). X-Ray Diffraction (XRD) and scanning electron microscope (SEM) studies revealed that layers grown on c-Al₂O₃ were fcc NiO with a dense morphology of cubic grains that were strongly (111) oriented along the growth direction. The relatively low ω rocking curve linewidth, of 0.12°suggests that there may have been epitaxial growth on the c-Al₂O₃ substrate. XRD and SEM indicated that films grown on Si (111) were also fcc NiO, with cubic grains, but that the grain orientation was random. This is consistent with the presence of an amorphous SiO₂ layer at the surface of the Si substrate, which precluded epitaxial growth. NiO grown at lower temperature (200°C) on temperature-sensitive FTO/glass substrates showed no evidence of crystallinity in XRD and SEM studies. After flash annealing in air, however, peaks characteristic of randomly oriented fcc NiO appeared in the XRD scans and the surface morphology became more granular in appearance. Such layers appear promising for the development of future dye-sensitised solar cell devices based on NiO grown by PLD. [reprint (PDF)]
1.	*A Crystallographic Model of (001) Aluminum Nitride Epitaxial Thin Film Growth on (001) Sapphire Substrate* C.J. Sun, P. Kung, A. Saxler, H. Ohsato, M. Razeghi, and K. Haritos Journal of Applied Physics 75 (8)-- April 15, 1994 ...[Visit Journal] A direct comparison of the physical properties of GaN thin films is made as a function of the choice of substrate orientations. Gallium nitride single crystals were grown on (0001) and (011-bar 2) sapphire substrates by metalorganic chemical vapor deposition. Better crystallinity with fine ridgelike facets is obtained on the (011-bar 2) sapphire. Also lower carrier concentration and higher mobilities indicate both lower nitrogen vacancies and less oxygen incorporation on the (011-bar 2) sapphire. The results of this study show better physical properties of GaN thin films achieved on (011-bar 2) sapphire. [reprint (PDF)]
1.	High-quality visible-blind AlGaN p-i-n photodiodes E. Monroy, M. Hamilton, D. Walker, P. Kung, F.J. Sanchez, and M. Razeghi Applied Physics Letters 74 (8)-- February 22, 1999 ...[Visit Journal] We report the fabrication and characterization of Al_xGa_1−xN p-i-n photodiodes (0 < x < 0.15) grown on sapphire by low-pressure metalorganic chemical vapor deposition. The devices present a visible rejection of six orders of magnitude with a cutoff wavelength that shifts from 365 to 338 nm. Photocurrent decays are exponential for high load resistances, with a time constant that corresponds to the RC product of the system. For low load resistances, the transient response becomes non-exponential, with a decay time longer than the RC constant. This behavior is justified by the strong frequency dependence of the device capacitance. By an admittance analysis, we conclude that speed is not limited by deep levels, but by substitutional Mg capture and emission time. [reprint (PDF)]
1.	High Detectivity InGaAs/InGaP Quantum-Dot Infrared Photodetectors Grown by Low Pressure Metalorganic Chemical Vapor Deposition J. Jiang, S. Tsao, T. O'Sullivan, W. Zhang, H. Lim, T. Sills, K. Mi, M. Razeghi, G.J. Brown, and M.Z. Tidrow Applied Physics Letters, 84 (12)-- April 22, 2004 ...[Visit Journal] We report a high detectivity middle-wavelength infrared quantum dot infrared photodetector (QDIP). The InGaAs quantum dots were grown by self-assembly on an InGaP matrix via low pressure metalorganic chemical vapor deposition. Photoresponse was observed at temperatures above 200 K with a peak wavelength of 4.7 µm and cutoff wavelength of 5.2 µm. The background limited performance temperature was 140 K, and this was attributed to the super low dark current observed in this QDIP. A detectivity of 3.6×10¹⁰ cm·Hz^½/W, which is comparable to the state-of-the-art quantum well infrared photodetectors in a similar wavelength range, was obtained for this InGaAs/InGaP QDIP at both T = 77 K and T = 95 K at biases of –1.6 and –1.4 V, [reprint (PDF)]
1.	Recent advances in high performance antimonide-based superlattice FPAs E.K. Huang, B.M. Nguyen, S.R. Darvish, S. Abdollahi Pour, G. Chen, A. Haddadi, and M.A. Hoang SPIE Proceedings, Infrared technology and Applications XXXVII, Orlando, FL, Vol. 8012, p. 80120T-1-- April 25, 2011 ...[Visit Journal] Infrared detection technologies entering the third generation demand performances for higher detectivity, higher operating temperature, higher resolution and multi-color detection, all accomplished with better yield and lower manufacturing/operating costs. Type-II antimonide based superlattices (T2SL) are making firm steps toward the new era of focal plane array imaging as witnessed in the unique advantages and significant progress achieved in recent years. In this talk, we will present the four research themes towards third generation imagers based on T2SL at the Center for Quantum Devices. High performance LWIR megapixel focal plane arrays (FPAs) are demonstrated at 80K with an NEDT of 23.6 mK using f/2 optics, an integration time of 0.13 ms and a 300 K background. MWIR and LWIR FPAs on non-native GaAs substrates are demonstrated as a proof of concept for the cost reduction and mass production of this technology. In the MWIR regime, progress has been made to elevate the operating temperature of the device, in order to avoid the burden of liquid nitrogen cooling. We have demonstrated a quantum efficiency above 50%, and a specific detectivity of 1.05x10¹² cm·Hz^1/2/W at 150 K for 4.2 μm cut-off single element devices. Progress on LWIR/LWIR dual color FPAs as well as novel approaches for FPA fabrication will also be discussed. [reprint (PDF)]
1.	Passivation of Type-II InAs/GaSb Superlattice Photodiodes A. Gin, Y. Wei, J. Bae, A. Hood, J. Nah, and M. Razeghi International Conference on Metallurgical Coatings and Thin Films (ICMCTF), San Diego, CA; Thin Solid Films 447-448-- January 30, 2004 ...[Visit Journal] Recently, excellent infrared detectors have been demonstrated using Type-II InAs/GaSb superlattice materials sensitive at wavelengths from 3 μm to greater than 32 μm. These results indicate that Type-II superlattice devices may challenge the preponderance of HgCdTe and other state-of-the-art infrared material systems. As such, surface passivation is becoming an increasingly important issue as progress is made towards the commercialization of Type-II devices and focal plane array applications. This work focuses on initial attempts at surface passivation of Type-II InAs/GaSb superlattice photodiodes using PECVD-grown thin layers of SiO₂. Our results indicate that silicon dioxide coatings deposited at various temperatures improve photodetector resistivity by several times. Furthermore, reverse-bias dark current has been reduced significantly in passivated devices. [reprint (PDF)]
1.	Aluminum nitride films on different orientations of sapphire and silicon K. Dovidenko, S. Oktyabrsky, J. Narayan, and M. Razeghi Journal of Applied Physics79 (5)-- March 1, 1996 ...[Visit Journal] The details of epitaxial growth and microstrictural characteristics of AlN films grown on sapphire (0001), (1012) and Si (100), (111) substrates were investigated using plan‐view and cross‐sectional high‐resolution transmission electron microscopy and x‐ray diffraction techniques. The films were grown by metalorganic chemical vapor deposition using TMA1+NH3+N2 gas mixtures. Different degrees of epitaxy were observed for the films grown on α‐Al₂O₃ and Si substrates in different orientations. The epitaxial relationship for (0001) sapphire was found to be (0001)AlN∥(0001)sap with in‐plane orientation relationship of [0110]AlN∥[1210]sap. This is equivalent to a 30° rotation in the basal (0001) plane. For (1012) sapphire substrates, the epitaxial relationship was determined to be (1120)AlN∥(1012)sap with the in‐plane alignment of [0001]AlN∥[1011]sap. The AlN films on (0001) α‐Al₂O₃ were found to contain inverted domain boundaries and a/3〈1120〉 threading dislocations with the estimated density of 10¹⁰ cm⁻². The density of planar defects (stacking faults) found in AlN films was considerably higher in the case of (1012) compared to (0001) substrates. Films on Si substrates were found to be highly textured c axis oriented when grown on (111) Si, and c axis textured with random in‐plane orientation on (100) Si. The role of thin‐film defects and interfaces on device fabrication is discussed. [reprint (PDF)]
1.	Persistent photoconductivity and the quantized Hall effect in In0.53Ga0.47As/InP heterostructures H. P. Wei; D. C. Tsui; M. Razeghi H. P. Wei, D. C. Tsui, M. Razeghi; Persistent photoconductivity and the quantized Hall effect in In0.53Ga0.47As/InP heterostructures. Appl. Phys. Lett. 15 September 1984; 45 (6): 666–668.-- September 15, 1984 ...[Visit Journal] A persistent photoconductivity is observed in the transport of the high mobility two‐dimensional electron gas in In0.53Ga0.47 As/InP heterostructures. Low field Hall measurements from 300 to 4.2 K and the quantized Hall effect in the high field limit are studied with radiation from visible and infrared light‐emitting diodes. Our results demonstrate conclusively that the effect is due to photogeneration of electron‐hole pairs in the heterostructure and trapping of holes in the In0.53Ga0.47 As. [reprint (PDF)]
1.	Solar-Blind Al_xGa_1-xN p-i-n Photodetectors grown on LEO and non-LEO GaN P. Sandvik, D. Walker, P. Kung, K. Mi, F. Shahedipour, V. Kumar, X. Zhang, J. Diaz, C. Jelen, and M. Razeghi SPIE Conference, San Jose, CA, Vol. 3948, pp. 265 -- January 26, 2000 ...[Visit Journal] The III-Nitride material system is an excellent candidate for UV photodetector applications due to its wide, direct bandgaps and robust material nature. However, despite many inherent material advantages, the III-Nitride material system typically suffers from a large number of extended defects which degrade material quality and device performance. One technique aimed at reducing defect densities in these materials is lateral epitaxial overgrowth (LEO). In this work, we present a preliminary comparison between AlGaN UV, solar-blind p-i-n photodiodes fabricated form LEO GaN and non-LEO GaN. Improvements in both responsivity and rejection ratio are observed, however, further device improvements are necessary. For these, we focus on the optimization of the p- i-n structure and a reduction in contact resistivity to p- GaN and p-AlGaN layers. By improving the structure of the device, GaN p-i-n photodiodes were fabricated and demonstrate 86 percent internal quantum efficiency at 362 nm and a peak to visible rejection ratio of 105. Contact treatments have reduced the contact resistivity to p-GaN and p-AlGaN by over one order of magnitude form our previous results. [reprint (PDF)]
1.	Pressure-induced depopulation of the first excited subband in GaInAs/InP heterojunctions D Gauthier, J C Portal and M Razeghi D Gauthier et al 1989 Semicond. Sci. Technol. 4 218-- December 8, 1988 ...[Visit Journal] Following our previous work on (GalnAs)/(lnP) heterojunctions under hydrostatic pressure we present recent experimental results where the evidence for the total depopulation of the first excited electric subband with pressure is demonstrated. The total electron concentration decreases at a rate of 2.7% kbar”, much higher than in previous experiments. The experimental situation can be fitted with the triangular-well approximation if we both assume the change with pressure of the conduction band discontinuity AE, and the deepening of a deep impurity level with activation energy of the order 160 meV at zero pressure. [reprint (PDF)]
1.	Geiger-mode operation of back-illuminated GaN avalanche photodiodes J. L. Pau, R. McClintock, K. Minder, C. Bayram, P. Kung, M. Razeghi, E. Muñoz, and D. Silversmith Applied Physics Letters, Vol. 91, No. 04, p. 041104 -1-- July 23, 2007 ...[Visit Journal] We report the Geiger-mode operation of back-illuminated GaN avalanche photodiodes fabricated on transparent AlN templates specifically for back illumination in order to enhance hole-initiated multiplication. The spectral response in Geiger-mode operation was analyzed under low photon fluxes. Single photon detection capabilities were demonstrated in devices with areas ranging from 225 to 14,063 µm². Single photon detection efficiency of 20% and dark count rate < 10 kHz were achieved in the smallest devices. [reprint (PDF)]
1.	High performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices A.M. Hoang, G. Chen, A. Haddadi and M. Razeghi SPIE Proceedings, Vol. 8631, p. 86311K-1, Photonics West, San Francisco, CA-- February 5, 2013 ...[Visit Journal] Active and passive imaging in a single camera based on the combination of short-wavelength and mid-wavelength infrared detection is highly needed in a number of tracking and reconnaissance missions. Due to its versatility in band-gap engineering, Type-II InAs/GaSb/AlSb superlattice has emerged as a candidate highly suitable for this multi-spectral detection. In this paper, we report the demonstration of high performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 μm and 4 μm. Taking advantages of the high performance short-wavelength and mid-wavelength single color photodetectors, back-to-back p-i-n-n-i-p photodiode structures were grown on GaSb substrate by molecular beam epitaxy. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0x10^-9 A/cm² at -50 mV bias voltage, providing an associated shot noise detectivity of 3.0x10¹³ Jones. The mid-wavelength channel exhibited a quantum efficiency of 33% and a dark current density of 2.6x10^-5 A/cm² at 300 mV bias voltage, resulting in a detectivity of 4.0x10¹¹ Jones. The operations of the two absorber channels are selectable by changing the polarity of applied bias voltage. [reprint (PDF)]
1.	Demonstration of high performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices A.M. Hoang, G. Chen, A. Haddadi and M. Razeghi Applied Physics Letters, Vol. 102, No. 1, p. 011108-1-- January 7, 2013 ...[Visit Journal] High performance bias-selectable dual-band short-/mid-wavelength infrared photodetector based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 μm and 4 μm was demonstrated. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0 × 10⁻⁹ A/cm² at −50 mV bias voltage, providing an associated shot noise detectivity of 3.0 × 10¹³ Jones. The mid-wavelength channel exhibited a quantum efficiency of 33% and a dark current density of 2.6 × 10⁻⁵ A/cm² at 300 mV bias voltage, resulting in a detectivity of 4.0 × 10¹¹ Jones. The spectral cross-talk between the two channels was also discussed for further optimization. [reprint (PDF)]
1.	Bias-selectable dual-band mid-/long-wavelength infrared photodetectors based on InAs/InAs_1−xSb_x type-II superlattices A. Haddadi, R. Chevallier, G. Chen, A. M. Hoang, and M. Razeghi Applied Physics Letters 106 , 011104-- January 8, 2015 ...[Visit Journal] A high performance bias-selectable mid-/long-wavelength infrared photodetector based on InAs/InAs_1−xSb_x type-II superlattices on GaSb substrate has been demonstrated. The mid- and long-wavelength channels' 50% cut-off wavelengths were ∼5.1 and ∼9.5 μm at 77 K. The mid-wavelength channel exhibited a quantum efficiency of 45% at 100 mV bias voltage under front-side illumination and without any anti-reflection coating. With a dark current density of 1 × 10⁻⁷ A/cm² under 100 mV applied bias, the mid-wavelength channel exhibited a specific detectivity of 8.2 × 10¹² cm·Hz^½·W^-1 at 77 K. The long-wavelength channel exhibited a quantum efficiency of 40%, a dark current density of 5.7 × 10⁻⁴ A/cm² under −150 mV applied bias at 77 K, providing a specific detectivity value of 1.64 × 10¹¹ cm·Hz^½·W^-1. [reprint (PDF)]
1.	Avalanche Photodetector Based on InAs/InSb Superlattice Arash Dehzangi, Jiakai Li, Lakshay Gautam and Manijeh Razeghi Quantum rep. 2020, 2(4), 591-599; https://doi.org/10.3390/quantum2040041 (registering DOI)-- December 4, 2020 ...[Visit Journal] This work demonstrates a mid-wavelength infrared InAs/InSb superlattice avalanche photodiode (APD). The superlattice APD structure was grown by molecular beam epitaxy on GaSb substrate. The device exhibits a 100 % cut-off wavelength of 4.6 µm at 150 K and 4.30 µm at 77 K. At 150 and 77 K, the device responsivity reaches peak values of 2.49 and 2.32 A/W at 3.75 µm under −1.0 V applied bias, respectively. The device reveals an electron dominated avalanching mechanism with a gain value of 6 at 150 K and 7.4 at 77 K which was observed under −6.5 V bias voltage. The gain value was measured at different temperatures and different diode sizes. The electron and hole impact ionization coefficients were calculated and compared to give a better prospect of the performance of the device. [reprint (PDF)]
1.	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 ...[Visit Journal] 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 (PDF)]
1.	Growth and Characterization of Type-II Non-Equilibrium Photovoltaic Detectors for Long Wavelength Infrared Range H. Mohseni, J. Wojkowski, A. Tahraoui, M. Razeghi, G. Brown and W. Mitche SPIE Conference, San Jose, CA, -- January 26, 2000 ...[Visit Journal] Growth and characterization of type-II detectors for mid-IR wavelength range is presented. The device has a p-i-n structure is designed to operate in the non-equilibrium mode with low tunneling current. The active layer is a short period InAs/GaSb superlattice. Wider bandgap p-type AlSb and n-type InAs layers are used to facilitate the extraction of both electronics and holes from the active layer for the first time. The performance of these devices were compared to the performance of devices grown at the same condition, but without the AlSb barrier layers. The processed devices with the AlSb barrier show a peak responsivity of about 1.2 A/W with Johnson noise limited detectivity of 1.1 X 10¹¹ cm·Hz^½/W at 8 μm at 80 K at zero bias. The details of the modeling, growth, and characterizations will be presented. [reprint (PDF)]

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