Center for Quantum Devices - Most Downloaded Journal Articles

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15.	Growth and Optimization of GaInAsP/InP Material System for Quantum Well Infrared Photodetector Applications M. Erdtmann, J. Jiang, A. Matlis, A. Tahraoui, C. Jelen, M. Razeghi, and G. Brown SPIE Conference, San Jose, CA, -- January 26, 2000 ...[Visit Journal] Multi-quantum well structures of Ga_xIn_1-xAs_yP_1-y were grown by metalorganic chemical vapor deposition for the fabrication of quantum well IR photodetectors. The thickness and composition of the wells was determined by high-resolution x-ray diffraction and photoluminescence experiments. The intersubband absorption spectrum of the Ga_0.47In_0.53As/InP, Ga_0.38In_0.62As_0.80P_0.20 (1.55 μm)/InP, and Ga_0.27In_0.73As_0.57P_0.43 (1.3 μm))/InP quantum wells are found to have cutoff wavelengths of 9.3 μm, 10.7 micrometers , and 14.2 μm respectively. These wavelengths are consistent with a conduction band offset to bandgap ratio of approximately 0.32. Facet coupled illumination responsivity and detectivity are reported for each composition. [reprint (PDF)]
15.	AlGaN ultraviolet photoconductors grown on sapphire D. Walker, X. Zhang, P. Kung, A. Saxler, S. Javadpour, J. Xu, and M. Razeghi Applied Physics Letters 68 (15)-- April 8, 1996 ...[Visit Journal] Al_xGa_1−xN (0≤x≤0.50) ultraviolet photoconductors with a minimum cutoff wavelength shorter than 260 nm have been fabricated and characterized. The AlGaN active layers were grown on (00⋅1) sapphire substrates by metalorganic chemical vapor deposition (MOCVD). The spectral responsivity of the GaN detector at 360 nm is about 1 A/W biased at 8 V at room temperature. The carrier lifetime derived from the voltage‐dependent responsivity is 0.13–0.36 ms. [reprint (PDF)]
15.	Optical Investigations of GaAs-GaInP Quantum Wells Grown on the GaAs, InP, and Si Substrates H. Xiaoguang, M. Razeghi Applied Physics Letters 61 (14)-- October 5, 1992 ...[Visit Journal] We report the first photoluminescence investigation of GaAs‐Ga_0.51In_0.49P lattice matched multiquantum wells grown by the low pressure metalorganic chemical vapor deposition simultaneously in the same run on GaAs, Si, and InP substrates. The sharp photoluminescence peaks indicate the high quality of the samples on three different substrates. The temperature dependence of the photoluminescence indicates that the intrinsic excitonic transitions dominate at low temperature and free‐carrier recombinations at room temperature. The photoluminescence peaks of the samples grown on Si and InP substrates shift about 15 meV from the corresponding peaks of the sample grown on the GaAs substrate. Two possible interpretations are provided for the observed energy shift. One is the diffusion of In along the dislocation threads from GaInP to GaAs and another is the localized strain induced by defects and In segregations. [reprint (PDF)]
15.	Quantum Sensing Using Type-II InAs/GaSb Superlattice for Infrared Detection M. Razeghi, A. Gin, Y. Wei, J. Bae, and J. Nah Microelectronics Journal, 34 (5-8)-- May 1, 2003 ...[Visit Journal] Large, regular arrays of bulk GaSb and InAs/GaSb Type-II superlattice pillars have been fabricated by electron beam lithography and dry etching. A 2.5 keV electron beam lithography system and metal evaporation are used to form the Au mask on superlattice and bulk substrates. Dry etching of these materials has been developed with BCl3:Ar, CH4:H2:Ar and cyclic CH₄:H₂:Ar/O₂ plasmas. Etch temperatures were varied from 20 to 150 °C. The diameter of the superlattice pillars was below 50 nm with regular 200 nm spacing. Bulk GaSb pillars were etched with diameters below 20 nm. Areas of dense nanopillars as large as 500 μm×500 μm were fabricated. The best height/diameter aspect ratio was approximately 10:1. To date, these are the smallest diameter III–V superlattice pillar structures reported, and the first nanopillars in the InAs/GaSb material system. The basic theory of these devices and surface passivation with SiO₂ and Si₃N₄ thin films has also been discussed. [reprint (PDF)]
15.	Comparison of ZnO nanostructures grown using pulsed laser deposition, metal organic chemical vapor deposition, and physical vapor transport V.E. Sandana, D.J. Rogers, F. Hosseini Teherani, R. McClintock, C. Bayram, M. Razeghi, H-J Drouhin, M.C. Clochard, V. Sallett, G. Garry, and F. Falyouni Journal of Vacuum Science and Technology B, Vol. 27, No. 3, May/June, p. 1678-1683-- May 29, 2009 ...[Visit Journal] This article compares the forms and properties of ZnO nanostructures grown on Si (111) and c-plane sapphire (c-Al₂O₃) substrates using three different growth processes: metal organic chemical vapor deposition (MOCVD), pulsed laser deposition (PLD), and physical vapor transport (PVT). A very wide range of ZnO nanostructures was observed, including nanorods, nanoneedles, nanocombs, and some novel structures resembelling “bevelled” nanowires. PVT gave the widest family of nanostructures. PLD gave dense regular arrays of nanorods with a preferred orientation perpendicular to the substrate plane on both Si and c-Al₂O₃ substrates, without the use of a catalyst. X-ray diffraction (XRD) studies confirmed that nanostructures grown by PLD were better crystallized and more highly oriented than those grown by PVT and MOCVD. Samples grown on Si showed relatively poor XRD response but lower wavelength emission and narrower linewidths in PL studies. [reprint (PDF)]
15.	Growth and Characterization of Very Long Wavelength Type-II Infrared Detectors H. Mohseni, A. Tahraoui, J. Wojkowski, M. Razeghi, W. Mitchel, and A. Saxler SPIE Conference, San Jose, CA, -- January 26, 2000 ...[Visit Journal] We report on the growth and characterization of type-II IR detectors with a InAs/GaSb superlattice active layer in the 15-19 μm wavelength range. The material was grown by molecular beam epitaxy on semi-insulating GaAs substrates. The material was processed into photoconductive detectors using standard photolithography, dry etching, and metalization. The 50 percent cut-off wavelength of the detectors is about 15.5 μm with a responsivity of 90 mA/W at 80 K. The 90 percent-10 percent cut-off energy width of the responsivity is only 17 meV which is an indication of the uniformity of the superlattices. These are the best reported values for type-II superlattices grown on GaAs substrates. [reprint (PDF)]
15.	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 ...[Visit Journal] 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 Hg_1-xCd_xTe. 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 (PDF)]
15.	Fabrication of GaN Nanotubular Material using MOCVD with an Aluminium Oxide Membrane W.G. Jung, S.H. Jung, P. Kung, and M. Razeghi Nanotechnology 17-- January 1, 2006 ...[Visit Journal] GaN nanotubular material is fabricated with an aluminium oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminium oxide membrane with ordered nanoholes is used as a template. Gallium nitride is deposited at the inner wall of the nanoholes in the aluminium oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis conditions in MOCVD are obtained successfully for the gallium nitride nanotubular material in this research. The diameter of the GaN nanotube fabricated is approximately 200–250 nm and the wall thickness is about 40–50 nm. [reprint (PDF)]
15.	Optical Investigations of GaAs-GaInP Quantum Wells and Superlattices Grown by Metalorganic Chemical Vapor Deposition Omnes F., and Razeghi M. Applied Physics Letters 59 (9), p. 1034-- May 28, 1991 ...[Visit Journal] Recent experimental results on the photoluminescence and photoluminescence excitation of GaAs‐Ga_0.51In_0.49P lattice‐matched quantum wells and superlattices are discussed. The full width at half maximum of a 10‐period GaAs‐GaInP superlattice with Lz=90 Å and LB=100 Å is 4 meV at 4 K. The photoluminescence excitation exhibits very sharp peaks attributed to the electron to light‐hole and electron to heavy‐hole transitions. The GaInP‐GaAs interface suffers from memory effect of In, rather than P or As elements. [reprint (PDF)]
15.	Crystallography of epitaxial growth of wurtzite-type thin films on sapphire substrates P. Kung, C.J. Sun, A. Saxler, H. Ohsato, and M. Razeghi Journal of Applied Physics 75 (9)-- May 1, 1994 ...[Visit Journal] In this article, we present a crystallographic model to describe the epitaxial growth of wurtzite‐type thin films such as gallium nitride (GaN) on different orientations of sapphire (Al2O3) substrates. Through this model, we demonstrate the thin films grown on (00⋅1)Al₂O₃ have a better epilayer‐substrate interface quality than those grown on (01⋅2)Al₂O₃. We also show the epilayer grown on (00⋅1)Al₂O₃ are gallium‐terminated, and both (00⋅1) and (01⋅2) surfaces of sapphire crystals are oxygen‐terminated. [reprint (PDF)]
15.	Mid-wavelength infrared high operating temperature pBn photodetectors based on type-II InAs/InAsSb superlattice Donghai Wu, Jiakai Li, Arash Dehzangi, and Manijeh Razeghi AIP Advances 10, 025018-- February 11, 2020 ...[Visit Journal] A high operating temperature mid-wavelength infrared pBn photodetector based on the type-II InAs/InAsSb superlattice on a GaSb substrate has been demonstrated. At 150 K, the photodetector exhibits a peak responsivity of 1.48 A/W, corresponding to a quantum efficiency of 47% at −50 mV applied bias under front-side illumination, with a 50% cutoff wavelength of 4.4 μm. With an R×A of 12,783 Ω·cm² and a dark current density of 1.16×10⁻⁵A/cm² under −50 mV applied bias, the photodetector exhibits a specific detectivity of 7.1×10¹¹ cm·Hz^½/W. At 300 K, the photodetector exhibits a dark current density of 0.44 A/cm²and a quantum efficiency of 39%, resultingin a specific detectivity of 2.5×10⁹ cm·Hz^½/W. [reprint (PDF)]
15.	Shortwave quantum cascade laser frequency comb for multi-heterodyne spectroscopy Q. Y. Lu, S. Manna, D. H. Wu, S. Slivken, and M. Razeghi Applied Physics Letters 112, 141104-- April 3, 2018 ...[Visit Journal] Quantum cascade lasers (QCLs) are versatile light sources with tailorable emitting wavelengths covering the mid-infrared and terahertz spectral ranges. When the dispersion is minimized, frequency combs can be directly emitted from quantum cascade lasers via four-wave mixing. To date, most of the mid-infrared quantum cascade laser combs are operational in a narrow wavelength range wherein the QCL dispersion is minimal. In this work, we address the issue of very high dispersion for shortwave QCLs and demonstrate 1-W dispersion compensated shortwave QCL frequency combs at λ~5.0 μm, spanning a spectral range of 100 cm⁻¹. The multi-heterodyne spectrum exhibits 95 equally spaced frequency comb lines, indicating that the shortwave QCL combs are ideal candidates for high-speed high-resolution spectroscopy [reprint (PDF)]
15.	InAs/InAs_1-xSb_x type-II superlattices for high performance long wavelength infrared detection A. Haddadi , G. Chen , R. Chevallier , A. M. Hoang , and M. Razeghi Appl. Phys. Lett. 105, 121104 (2014)-- September 22, 2014 ...[Visit Journal] High performance long-wavelength infrared nBn photodetectors based on InAs/InAs_1−xSb_x type-II superlattices on GaSb substrate have been demonstrated. The photodetector's 50% cut-off wavelength was ∼10 μm at 77 K. The photodetector with a 6 μm-thick absorption region exhibited a peak responsivity of 4.47 A/W at 7.9 μm, corresponding to a quantum efficiency of 54% at −90 mV bias voltage under front-side illumination and without any anti-reflection coating. With an R × A of 119 Ω·cm² and a dark current density of 4.4 × 10⁻⁴ A/cm² under −90 mV applied bias at 77 K, the photodetector exhibited a specific detectivity of 2.8 × 10¹¹ cm·Hz^1/2·W^-1. [reprint (PDF)]
15.	Determination of of Band Gap Energy of Al_1-xIn_xN Grown by Metal Organic Chemical Vapor Deposition in the High Al Composition Regime K.S. Kim, A. Saxler, P. Kung, M. Razeghi, and K.Y. Lim Applied Physics Letters 71 (6)-- August 11, 1997 ...[Visit Journal] Ternary AlInN was grown by metal–organic chemical-vapor deposition in the high Al composition regime. The band-gap energy of AlInN ternary was measured by optical absorption spectroscopy at room temperature. The band-gap energy of Al_0.92In_0.08N is 5.26 eV. The potential application of AlInN as a barrier material for GaN is also discussed. [reprint (PDF)]
15.	Recent advances in antimonide-based gap-engineered Type-II superlattices material system for 2 and 3 colors infrared imagers Manijeh. Razeghi, Abbas Haddadi, Arash Dehzangi, Romain Chevallier, and Thomas Yang Proceedings of SPIE 10177, Infrared Technology and Applications XLIII, 1017705-- May 9, 2017 ...[Visit Journal] InAs/InAs_1-xSb_x/AlAs_1-xSb_x type-II superlattices (T2SLs) is a system of multi-interacting quantum wells. Since its introduction, this material system has drawn a lot of attention especially for infrared detection. In recent years, InAs/InAs_1- xSb_x/AlAs_1-xSb_x T2SL material system has experienced incredible improvements in material quality, device structure designs and device fabrication process which elevated the performances of T2SL-based photodetectors to a comparable level to the state-of-the-art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). In this paper, we will present the current status of InAs/InAs_1-xSb_x/AlAs_1-xSb_x T2SL-based photodetectors for detection in different infrared regions, from short-wavelength (SWIR) to long-wavelength (LWIR) infrared, and the future outlook of this material system. [reprint (PDF)]
15.	Efficiency of photoluminescence and excess carrier confinement in InGaAsP/GaAs structures prepared by metal-organic chemical vapor deposition J. Diaz, H.J. Yi, M. Erdtmann, X. He, E. Kolev, D. Garbuzov, E. Bigan, and M. Razeghi Journal of Applied Physics 76 (2)-- July 15, 1994 ...[Visit Journal] Special double‐ and separate‐confinement InGaAsP/GaAs heterostructures intended for photoluminescence measurements have been grown by low‐pressure metal‐organic chemical‐vapor deposition. The band gap of the active region quaternary material was close to 1.5 eV, and the waveguide of the separate‐confinement structures was near 1.8 eV. Measurement of the integrated luminescence efficiency at 300 K has shown that over a wide range of excitation level (10–10³ W/cm²) radiative transitions are the dominant mechanism for excess carrier recombination in the active region of the structures studied. As determined by spectral measurements, the excess carrier concentration in the waveguide of the separate‐confinement heterostructures and the intensity of the waveguide emission band correspond to a condition of thermal equilibrium of the excess carrier populations in the active region and the waveguide. The ratio of the intensity of the waveguide emission to the active region emission fits a model which assumes that the barrier height for minority carriers (holes) is equal to the difference in band gaps between the active region and the waveguide region. [reprint (PDF)]
15.	High-Power Continuous-Wave Operation of a 6 µm Quantum-Cascade Laser at Room Temperature J.S. Yu, S. Slivken, A. Evans, L. Doris, and M. Razeghi Applied Physics Letters, 83 (13)-- September 29, 2003 ...[Visit Journal] We report continuous-wave (cw) operation of quantum-cascade lasers (λ= 6 µm) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 308 K (35 °C). The high cw optical output powers of 132 mW at 293 K and 21 mW at 308 K are achieved with threshold current densities of 2.29 and 2.91 kA/cm², respectively, for a high-reflectivity-coated 15 µm wide and 2 mm long laser. [reprint (PDF)]
15.	Hybrid green LEDs with n-type ZnO substituted for N-type GaN in an inverted P-N junction F. Hosseini Teherani; M. Razeghi; D.J. Rogers; Can Bayram; R. McClintock LEOS Annual Meeting Conference Proceedings, LEOS '09. IEEE, [5343231] (2009) -- October 4, 2009 ...[Visit Journal] Recently, the GaN and ZnO materials systems have attracted considerable attention because of their use in a broad range of emerging applications including light-emitting diodes (LEDs) and solar cells. GaN and ZnO are similar materials with direct wide bandgaps, wurtzite crystal structure, high thermal stability and comparable thermal expansion coefficients, which makes them well suited for heterojunction fabrication. Two important advantages of GaN over ZnO are the reliable p-type doping and the mature know-how for bandgap engineering. Thus GaN-based LEDs can be made to emit from the deep UV right into the green through alloying with Al and In, respectively. The performance is not identical at all wavelengths, however, and the performance of InGaN-based green LEDs is still relatively poor. [reprint (PDF)]
15.	Molecular Beam Epitaxial Growth of High Quality InSb E. Michel, G. Singh, S. Slivken, C. Besikci, P. Bove, I. Ferguson, and M. Razeghi Applied Physics Letters 65 (26)-- December 26, 1994 ...[Visit Journal] In this letter we report on the growth of high quality InSb by molecular beam epitaxy that has been optimized using reflection high energy electron diffraction. A 4.8 µm InSb layer grown on GaAs at a growth temperature of 395 °C and a III/V incorporation ratio of 1:1.2 had an x-ray rocking curve of 158 arcsec and a Hall mobility of 92,300 cm²·V⁻¹ at 77 K. This is the best material quality obtained for InSb nucleated directly onto GaAs reported to date. [reprint (PDF)]
15.	Long-term reliability of Al-free InGaAsP/GaAs λ = 808 nm) lasers at high-power high-temperature operation J. Diaz, H. Yi, M. Razeghi and G.T. Burnham Applied Physics Letters 71 (21)-- November 24, 1997 ...[Visit Journal] We report the long-term reliability measurement on uncoated Al-free InGaAsP/GaAs (λ = 808 nm) lasers at high-power and high-temperature operation. No degradation in laser performance has been observed for over 30 ,000 h of lifetime testing in any of randomly selected several 100 μm-wide uncoated lasers operated at 60 °C with 1 W continuous wave output power. This is the first and the most conclusive evidence ever reported that directly shows the high long-term reliability of uncoated Al-free lasers. [reprint (PDF)]
15.	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)]
15.	Room temperature terahertz quantum cascade laser sources with 215 μW output power through epilayer-down mounting Q. Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai, and M. Razeghi Appl. Phys. Lett. 103, 011101 (2013)-- July 1, 2013 ...[Visit Journal] We report room temperature terahertz (THz) quantum cascade laser sources with high power based on difference frequency generation. The device is Čerenkov phase matched and spectrally purified with an integrated dual-period distributed-feedback grating. Symmetric current injection and epilayer-down mounting of the device onto a patterned submount are used to improve the electrical uniformity and heat removal, respectively. The epilayer-down mounting also allows for THz anti-reflective coating to enhance the THz outcoupling efficiency. Single mode emission at 3.5 THz with a side-mode suppression ratio and output power up to 30 dB and 215 μW are obtained, respectively. [reprint (PDF)]
15.	High differential resistance type-II InAs/GaSb superlattice photodiodes for the long-wavelength infrared A. Hood, D. Hoffman, B.M. Nguyen, P.Y. Delaunay, E. Michel and M. Razeghi Applied Physics Letters, 89 (9)-- August 28, 2006 ...[Visit Journal] Type-II InAs/GaSb superlattice photodiodes with a 50% cutoff wavelength ranging from 11 to 13 μm are presented. Optimization of diffusion limited photodiodes provided superlattice structures for improved injection efficiency in direct injection hybrid focal plane array applications. [reprint (PDF)]
15.	Broad area photonic crystal distributed feedback quantum cascade lasers emitting 34 W at λ ~ 4.36 μm B. Gokden, Y. Bai, N. Bandyopadhyay, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 97, No. 13, p. 131112-1-- September 27, 2010 ...[Visit Journal] We demonstrate room temperature, high power, single mode, and diffraction limited operation of a two dimensional photonic crystal distributed feedback quantum cascade laser emitting at 4.36 μm. Total peak power up to 34 W is observed from a 3 mm long laser with 400 μm cavity width at room temperature. Far-field profiles have M2 figure of merit as low as 2.5. This device represents a significant step toward realization of spatially and spectrally pure broad area high power quantum cascade lasers. [reprint (PDF)]
15.	Effect of sidewall surface recombination on the quantum efficiency in a Y₂O₃ passivated gated type-II InAs/GaSb long-infrared photodetector array G. Chen, A. M. Hoang, S. Bogdanov, A. Haddadi, S. R. Darvish, and M. Razeghi Appl. Phys. Lett. 103, 223501 (2013)-- November 25, 2013 ...[Visit Journal] Y₂O₃ was applied to passivate a long-wavelength infrared type-II superlattice gated photodetector array with 50% cut-off wavelength at 11 μm, resulting in a saturated gate bias that was 3 times lower than in a SiO₂ passivated array. Besides effectively suppressing surface leakage, gating technique exhibited its ability to enhance the quantum efficiency of 100 × 100 μm size mesa from 51% to 57% by suppressing sidewall surface recombination. At 77 K, the gated photodetector showed dark current density and resistance-area product at −300 mV of 2.5 × 10⁻⁵ A/cm² and 1.3 × 10⁴ Ω·cm², respectively, and a specific detectivity of 1.4 × 10¹² Jones. [reprint (PDF)]

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