Center for Quantum Devices - Most Downloaded Journal Articles

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16.	Pulsed metalorganic chemical vapor deposition of high quality AlN/GaN superlattices for intersubband transitions C. Bayram, B. Fain, N. Pere-Laperne, R. McClintock and M. Razeghi SPIE Proceedings, San Jose, CA Volume 7222-12-- January 26, 2009 ...[Visit Journal] A pulsed metalorganic chemical vapor deposition (MOCVD) technique, specifically designed for high quality AlN/GaN superlattices (SLs) is introduced. Optical quality and precise controllability over layer thicknesses are investigated. Indium is shown to improve interface and surface quality. An AlN/GaN SL designed for intersubband transition at a telecommunication wavelength of ~1.5 µm, is grown, and processed for intersubband (ISB) absorption measurements. Room temperature measurements show intersubband absorption centered at 1.49 µm. Minimal (n-type) silicon doping of the well is shown to be crucial for good ISB absorption characteristics. The potential to extend this technology into the far infrared and even the terahertz (THz) region is also discussed. [reprint (PDF)]
16.	High quantum efficiency back-illuminated GaN avalanche photodiodes C. Bayram, J.L. Pau, R. McClintock, M. Razeghi, M.P. Ulmer, and D. Silversmith Applied Physics Letters, Vol. 93, No. 21, p. 211107-1-- November 24, 2008 ...[Visit Journal] Back-illuminated avalanche photodiodes (APDs) composed of heterojunctions of either p-GaN/i-GaN/n-AlGaN or p-GaN/i-GaN/n-GaN/n-AlGaN were fabricated on AlN templates. At low voltage, an external quantum efficiency of 57% at 352 nm with a bandpass response was achieved by using AlGaN in the n-layer. Dependency of gain and leakage current on mesa area for these heterojunction APDs were studied. Back-illumination via different wavelength sources was used to demonstrate the advantages of hole-initiated multiplication in GaN APDs. [reprint (PDF)]
16.	Compressively-strained multiple quantum well InAsSb lasers emitting at 3.6 μm grown by metal-organic chemical vapor deposition B. Lane, D. Wu, A. Rybaltowski, H. Yi, J. Diaz, and M. Razeghi Applied Physics Letters 70 (4)-- January 27, 1997 ...[Visit Journal] A compressively strained InAsSb/InAs multiple quantum-well (MQW) structure was grown by low-pressure metal-organic chemical vapor deposition. Maximum output power (from two facets) up to 1 W with differential efficiency about 70% was obtained from a MQW laser with stripe width of 100 μm and cavity length of 700 μm for emitting wavelength of 3.65 μm at 90 K in pulse mode operation. About 2 times lower threshold current density was obtained from the MQW lasers for a temperature range of 90 to 140 K compared to the double heterostructure lasers grown on the same growth conditions. [reprint (PDF)]
16.	High Power 280 nm AlGaN Light Emitting Diodes Based on an Asymmetric Single Quantum Well K. Mayes, A. Yasan, R. McClintock, D. Shiell, S.R. Darvish, P. Kung, and M. Razeghi Applied Physics Letters, 84 (7)-- February 16, 2004 ...[Visit Journal] We demonstrate high-power AlGaN-based ultraviolet light-emitting diodes grown on sapphire with an emission wavelength of 280 nm using an asymmetric single-quantum-well active layer configuration on top of a high-quality AlGaN/AlN template layer. An output power of 1.8 mW at a pulsed current of 400 mA was achieved for a single 300 µm×300 µm diode. This device reached a high peak external quantum efficiency of 0.24% at 40 mA. An array of four diodes produced 6.5 mW at 880 mA of pulsed current. [reprint (PDF)]
16.	Demonstration of long wavelength infrared Type-II InAs/InAs_1-xSb_x superlattices photodiodes on GaSb substrate grown by metalorganic chemical vapor deposition D. H. Wu, A. Dehzangi, Y. Y. Zhang, M. Razeghi Applied Physics Letters 112, 241103-- June 12, 2018 ...[Visit Journal] We report the growth and characterization of long wavelength infrared type-II InAs/InAs_1−xSb_x superlattices photodiodes with a 50% cut-off wavelength at 8.0 μm on GaSb substrate grown by metalorganic chemical vapor deposition. At 77 K, the photodiodes exhibited a differential resistance at zero bias (R₀A) 8.0 Ω·cm², peak responsivity of 1.26 A/W corresponding to a quantum efficiency of 21%. A specific detectivity of 5.4×10¹⁰ cm·Hz^1/2/W was achieved at 7.5 μm. [reprint (PDF)]
16.	Investigation of surface leakage reduction for small pitch shortwave infrared photodetectors Arash Dehzangi, Quentin Durlin, Donghai Wu, Ryan McClintock, Manijeh Razeghi Semiconductor Science and Technology, 34(6), 06LT01-- May 25, 2019 ...[Visit Journal] Different passivation techniques are investigated for reducing leakage current in small pixel (down to 9 μm) heterostructure photodetectors designed for the short-wavelength infrared range. Process evaluation test chips were fabricated using the same process as for focal plane arrays. Arrays of small photodetectors were electrically characterized under dark conditions from 150 K to room temperature. In order to evaluate the leakage current, we studied the relation between the inverse of dynamic resistance at −20 mV and zero bias and perimeter over area P/A ratio as the pixel size is scaled down. At 150 K, leakage current arising from the perimeter dominates while bulk leakage dominates at room temperature. We find that in shortwave devices directly underfilling hybridized devices with a thermoset epoxy resin without first doing any additional passivation/protection after etching gives the lowest leakage with a surface resistance of 4.2 × 10⁹ and 8.9 × 10³ Ω· cm⁻¹ at 150 and 300 K, for −20 mV of bias voltage, respectively. [reprint (PDF)]
16.	Molecular beam epitaxial growth of InSb p-i-n photodetectors on GaAs and Si E. Michel, R. Peters, S. Slivken, C. Jelen, P. Bove, J. Xu, I. Ferguson, and M. Razeghi Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995 ...[Visit Journal] High quality InSb has been grown by Molecular Beam Epitaxy and optimized using Reflection High Energy Electron Diffraction. A 4.8 micrometers InSb layer grown on GaAs at a growth temperature of 395 degree(s)C and a III/V incorporation ratio of 1:1.2 had an X-ray rocking curve FWHM of 158 arcsec and a Hall mobility of 92300 cm2V-1s-1 at 77 K, the best reported to date for InSb nucleated directly onto GaAs. InSb p-i-n structures of 5.8 micrometers grown under the same conditions demonstrated a X-ray Full Width at Half Maximum of 101 arcsec and 131 arcsec for GaAs and Si substrates, respectively, and exhibited excellent uniformity of +/- 3 arcsec over a 3' substrate. Prototype InSb p-i-n detectors on Si have been fabricated and have demonstrated photovoltaic response at 6.5 micrometers up to 200 K. These p-i-n detectors have also exhibited the highest D* for a device grown onto Si. [reprint (PDF)]
16.	On the performance and surface passivation of type-II InAs/GaSb superlattice photodiodes for the very-long- wavelength infrared A. Hood, M. Razeghi, E. Aifer, G.J. Brown Applied Physics Letters 87 (1)-- October 10, 2005 ...[Visit Journal] We demonstrate very-long-wavelength infrared Type-II InAs/GaSb superlattice photodiodes with a cutoff wavelength (λ_c,50%) of 17 μm. We observed a zero-bias, peak Johnson noise-limited detectivity of 7.63×10⁹ cm·Hz^½/W at 77 K with a 90%-10% cutoff width of 17 meV, and quantum efficiency of 30%. Variable area diode zero-bias resistance-area product (R₀A) measurements indicated that silicon dioxide passivation increased surface resistivity by nearly a factor of 5, over unpassivated photodiodes, and increased overall R₀A uniformity. The bulk R₀A at 77 K was found to be 0.08 Ω·cm², with RA increasing more than twofold at 25 mV reverse bias. [reprint (PDF)]
16.	Highly Conductive Co-Doped Ga2O3Si-In Grown by MOCVD Junhee Lee, Honghyuk Kim, Lakshay Gautam and Manijeh Razeghi Coatings 2021, 11(3), 287; https://doi.org/10.3390/coatings11030287 ...[Visit Journal] We report a highly conductive gallium oxide doped with both silicon and indium grown on c-plane sapphire substrate by MOCVD. From a superlattice structure of indium oxide and gallium oxide doped with silicon, we obtained a highly conductive material with an electron hall mobility up to 150 cm2/V·s with the carrier concentration near 2 × 1017 cm−3. However, if not doped with silicon, both Ga2O3:In and Ga2O3 are highly resistive. Optical and structural characterization techniques such as X-ray, transmission electron microscope, and photoluminescence, reveal no significant incorporation of indium into the superlattice materials, which suggests the indium plays a role of a surfactant passivating electron trapping defect levels. [reprint (PDF)]
16.	High brightness angled cavity quantum cascade lasers D. Heydari, Y. Bai, N. Bandyopadhyay, S. Slivken, and M. Razeghi Applied Physics Letters 106, 091105-- March 6, 2015 ...[Visit Journal] A quantum cascade laser (QCL) with an output power of 203 W is demonstrated in pulsed mode at 283 K with an angled cavity. The device has a ridge width of 300 μm, a cavity length of 5.8 mm, and a tilt angle of 12°. The back facet is high reflection coated, and the front facet is anti-reflection coated. The emitting wavelength is around 4.8 μm. In distinct contrast to a straight cavity broad area QCL, the lateral far field is single lobed with a divergence angle of only 3°. An ultrahigh brightness value of 156 MW cm²·sr^-1 is obtained, which marks the brightest QCL to date. [reprint (PDF)]
16.	Monolithic integration of a short‐length GaInAs photoconductor with a GaAs/GaAlAs optical waveguide on a GaAs semi‐insulating substrate F. Mallecot; J. F. Vinchant; M. Razeghi; D. Vandermoere; J. P. Vilcot; D. Decoster Appl. Phys. Lett. 53, 2522–2524 (1988)-- December 19, 1988 ...[Visit Journal] We report the first fabrication of a GaO. 47 Inn. 53 As planar photoconductive detector, associated with a GaAs/GaAIAs rib waveguide grown on a semi-insulating GaAs substrate, which needs a short-length absorbing layer to detect the optical signal. Because of the GaAIAs epilayer, a GalnAs length of about 100 tl1n only is needed to detect 90% of the opticai signal, accordingly to results predicted using a four-layer model with complex refractive indices in each layer. [reprint (PDF)]
16.	High Performance InAs/InAsSb Type-II Superlattice Mid-Wavelength Infrared Photodetectors with Double Barrier Donghai Wu, Jiakai Li, Arash Dehzangi, Manijeh Razeghi Infrared Physics &Technology 103439-- July 18, 2020 ...[Visit Journal] By introducing a double barrier design, a high performance InAs/InAsSb type-II superlattice mid-wavelength infrared photodetector has been demonstrated. The photodetector exhibits a cut-off wavelength of ~4.50 µm at 150 K. At 150 K and −120 mV applied bias, the photodetector exhibits a dark current density of 1.21 × 10−5 A/cm2, a quantum efficiency of 45% at peak responsivity (~3.95 µm), and a specific detectivity of 6.9 × 1011 cm·Hz1/2/W. The photodetector shows background-limited operating temperature up to 160 K. [reprint (PDF)]
16.	Nitrides push performance of UV photodiodes Can Bayram; Manijeh Razeghi Laser Focus World. 45(9), pp. 47-51 (2009)-- September 1, 2009 ...[Visit Journal] The nitrides are known to be useful for creating the UV single-photon detectors with efficiencies of 20%, with its considerable advantages that could further enable quantum computing and data encryption. Such detectors would be well suited for numerous applications in the defense, commercial, and scientific arenas, including covert space-to-space communications, early missile-threat detection, chemical and biological threat detection and spectroscopy. The use of SAM regions is a common approach to reducing multiplication noise and enhancing gain through impact-ionization engineering that could benefit from the higher ionization coefficient by offering lower noise performance and higher gain. The ADPs also enables the realization of single-photon detection by using Geiger-mode operation, which entails operating the ADPs well above the breakdown voltage and using pulse-quenching circuitry. [reprint (PDF)]
16.	Low pressure metalorganic chemical vapor deposition of high quality AlN and GaN thin films on sapphire and silicon substrates P. Kung, X. Zhang, E. Bigan, and M. Razeghi Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995 ...[Visit Journal] High quality AlN and GaN epilayers have been grown on basal plane sapphire by low pressure metalorganic chemical vapor deposition. The X-ray rocking curve linewidth of the AlN and GaN films were about 100 and 30 arcsecs respectively. Sharp absorption edges were determined at 6.1 and 3.4 eV respectively. Successful donor-bound excitonic luminescence emissions were detected for GaN films grown on sapphire and silicon. Two additional lines at 3.37 and 3.31 eV were observed on GaN on sapphire and assumed to be impurity-related. Doping of GaN layers was achieved with magnesium. Mg-related photoluminescence emissions were successfully detected on as-grown samples, without any post-growth treatment. [reprint (PDF)]
16.	Negative luminescence of InAs/GaSb superlattice photodiodes F. Fuchs, D. Hoffman, A. Gin, A. Hood, Y. Wei, and M. Razeghi Phys. Stat. Sol. C 3 (3)-- February 22, 2006 ...[Visit Journal] The emission behaviour of InAs/GaSb superlattice photodiodes has been studied in the spectral range between 8 µm and 13 μm. With a radiometric calibration of the experimental set-up the internal quantum efficiency has been determined in the temperature range between 80 K and 300 K for both, the negative and positive luminescence. The quantitative analysis of the internal quantum efficiency of the non-equilibrium radiation enables the determination of the Auger coefficient. [reprint (PDF)]
16.	Investigations of p-type signal for ZnO thin films grown on (100) GaAs substrates by pulsed laser deposition D.J. Rogers, F. Hosseini Teherani, T. Monteiro, M. Soares, A. Neves, M. Carmo, S. Periera, M.R. Correia, A. Lusson, E. Alves, N.P. Barradas, J.K. Morrod, K.A. Prior, P. Kung, A. Yasan, and M. Razeghi Phys. Stat. Sol. C, 3 (4)-- March 1, 2006 ...[Visit Journal] n this work we investigated ZnO films grown on semi-insulating (100) GaAs substrates by pulsed laser deposition. Samples were studied using techniques including X-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy, Raman spectroscopy, temperature dependent photoluminescence, C-V profiling and temperature dependent Hall measurements. [reprint (PDF)]
16.	High-performance bias-selectable dual-band mid-/long-wavelength infrared photodetectors and focal plane arrays based on InAs/GaSb Type-II superlattices M. Razeghi; A. Haddadi; A.M. Hoang; G. Chen; S. Ramezani-Darvish; P. Bijjam Proc. SPIE 8704, Infrared Technology and Applications XXXIX, 87040S (June 11, 2013)-- June 11, 2013 ...[Visit Journal] We report a bias selectable dual-band mid-wave infrared (MWIR) and long-wave infrared (LWIR) co-located detector with 3 μm active region thickness per channel that is highly selective and can perform under high operating temperatures for the MWIR band. Under back-side illumination, a temperature evolution study of the MWIR detector's electro-optical performance found the 300 K background-limit with 2π field-of-view to be achieved below operating temperatures of 160 K, at which the temperature's 50% cutoff wavelength was 5.2 μm. The measured current reached the system limit of 0.1 pA at 110 K for 30 μm pixel-sized diodes. At 77 K, where the LWIR channel operated with a 50% cutoff wavelength at 11.2 μm, an LWIR selectivity of ∼17% was achieved in the MWIR wave band between 3 and 4.7 μm, making the detector highly selective. [reprint (PDF)]
16.	Type-II Superlattices and Quantum Cascade Lasers for MWIR and LWIR Free-Space Communications A. Hood, A. Evans and M. Razeghi SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 690005-1-9.-- February 1, 2008 ...[Visit Journal] Free-space optical communications has recently been touted as a solution to the "last mile" bottleneck of high-speed data networks providing highly secure, short to long range, and high-bandwidth connections. However, commercial near infrared systems experience atmospheric scattering losses and scintillation effects which can adversely affect a link's operating budget. By moving the operating wavelength into the mid- or long-wavelength infrared enhanced link uptimes and increased operating range can be achieved due to less susceptibility to atmospheric affects. The combination of room-temperature, continuous-wave, high-power quantum cascade lasers and high operating temperature type-II superlattice photodetectors offers the benefits of mid- and long-wavelength infrared systems as well as practical operating conditions for next generation free-space communications systems. [reprint (PDF)]
16.	III-Nitride avalanche photodiodes R. McClintock, J.L. Pau, C. Bayram, B. Fain, P. Giedratis, M. Razeghi and M. Ulmer SPIE Proceedings, San Jose, CA Volume 7222-0U-- January 26, 2009 ...[Visit Journal] Research into avalanche photodiodes (APDs) is motivated by the need for high sensitivity ultraviolet (UV) detectors in numerous civilian and military applications. By designing photodetectors to utilize low-noise impact ionization based gain, GaN APDs operating in Geiger mode can deliver gains exceeding 1×10⁷. Thus with careful design, it becomes possible to count photons at the single photon level. In this paper we review the current state of the art in III-Nitride visible-blind APDs, and present our latest results regarding linear and Geiger mode III-Nitride based APDs. This includes novel device designs such as separate absorption and multiplication APDs (SAM-APDs). We also discuss control of the material quality and the critical issue of p-type doping - demonstrating a novel delta-doping technique for improved material quality and enhanced electric field confinement. The spectral response and Geiger-mode photon counting performance of these devices are then analyzed under low photon fluxes, with single photon detection capabilities being demonstrated. Other major technical issues associated with the realization of high-quality visible-blind Geiger mode APDs are also discussed in detail and future prospects for improving upon the performance of these devices are outlined. [reprint (PDF)]
16.	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)]
16.	Growth of Deep UV Light Emitting Diodes by Metalorganic Chemical Vapor Deposition A. Yasan, R. McClintock, K. Mayes, D. Shiell, S. Darvish, P. Kung and M. Razeghi SPIE Conference, Jose, CA, Vol. 5359, pp. 400-- January 25, 2004 ...[Visit Journal] We demonstrate high power AlGaN based ultraviolet light-emitting diodes (UV LEDs) with an emission wavelength of 280 nm using an asymmetric single quantum well active layer configuration on top of a high-quality AlGaN/AlN template layer grown by metalorganic chemical vapor deposition (MOCVD). An output power of 1.8 mW at a pulsed current of 400 mA was achieved for a single 300 µm × 300 µm diode. This device reached a high peak external quantum efficiency of 0.24% at 40 mA. An array of four diodes produced 6.5 mW at 880 mA of pulsed current. [reprint (PDF)]
16.	High-brightness LWIR quantum cascade lasers F. Wang, S. Slivken, and M. Razeghi F. Wang, S. Slivken, and M. Razeghi, High-brightness LWIR quantum cascade lasers, Optics Letters, vol. 46, No. 20, 5193 ...[Visit Journal] Long-wave infrared (LWIR, lambda~8-12 um) quantum cascade lasers (QCLs) are drawing increasing interest, as they provide the possibility of long-distance transmission of light through the atmosphere owing to the reduced water absorption. However, their development has been lagging behind the shorter wavelength QCLs due to much bigger technological challenges. In this Letter, through band structure engineering based on a highly localized diagonal laser transition strategy and out-coupler design using an electrically isolated taper structure, we demonstrate high beam quality single-mode LWIR QCLs with high-brightness (2.0 MW cm^-2 sr^-1 for lambda~10 um, 2.2 MW cm^-2 sr^-1 for lambda~9 um, 5.0 MW cm^-2 sr^-1 for lambda~8 um) light extraction from a single facet in continuous-wave operation at 15 ^oC. These results mark an important milestone in exploring the lighting capability of inter-sub-band semiconductor lasers in the LWIR spectral range. [reprint (PDF)]
16.	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)]
16.	Comparison of the Physical Properties of GaN Thin Films Deposited on (0112) and (0001) Sapphire Substrates C.J. Sun and M. Razeghi Applied Physics Letters 63 (7)-- August 16, 1993 ...[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 (0112) sapphire substrates by metalorganic chemical vapor deposition. Better crystallinity with fine ridgelike facets is obtained on the (0112) sapphire. Also lower carrier concentration and higher mobilities indicate both lower nitrogen vacancies and less oxygen incorporation on the (0112) sapphire. The results of this study show better physical properties of GaN thin films achieved on (0112) sapphire. [reprint (PDF)]
16.	Continuous operation of a monolithic semiconductor terahertz source at room temperature Q. Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai, and M. Razeghi Appl. Phys. Lett. 104, 221105 (2014)-- June 3, 2014 ...[Visit Journal] We demonstrate room temperature continuous wave THz sources based on intracavity difference-frequency generation from mid-infrared quantum cascade lasers. Buried ridge, buried composite distributed-feedback waveguide with Čerenkov phase-matching scheme is used to reduce the waveguide loss and enhance the heat dissipation for continuous wave operation. Continuous emission at 3.6 THz with a side-mode suppression ratio of 20 dB and output power up to 3 μW are achieved, respectively. THz peak power is further scaled up to 1.4 mW in pulsed mode by increasing the mid-infrared power through increasing the active region doping and device area. [reprint (PDF)]

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