Center for Quantum Devices - Most Downloaded Journal Articles

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19.	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)]
19.	A Review of III-Nitride Research at the Center for Quantum Devices M. Razeghi and R. McClintock Journal of Crystal Growth, Vol. 311, No. 10-- May 1, 2009 ...[Visit Journal] In this paper, we review the history of the Center for Quantum Devices’ (CQD) III-nitride research covering the past 15 years. We review early work developing III-nitride material growth. We then present a review of laser and light-emitting diode (LED) results covering everything from blue lasers to deep UV LEDs emitting at 250 nm. This is followed by a discussion of our UV photodetector research from early photoconductors all the way to current state of the art Geiger-mode UV single photon detectors. [reprint (PDF)]
19.	Investigation of Enhanced Heteroepitaxy and Electrical Properties in k-Ga2O3 due to Interfacing with β-Ga2O3 Template Layers Junhee Lee, Lakshay Gautam, Ferechteh H. Teherani, Eric V. Sandana, P. Bove, David J. Rogers and Manijeh Razeghi J. Lee, M. Razeghi, Physica Status Solidi A 2023,220, 2200559, https://doi.org/10.1002/pssa.202200559 ...[Visit Journal] Heteroepitaxial k-Ga2O3 films grown by metal-organic chemical vapor deposition (MOCVD) were found to have superior materials and electrical properties thanks to the interfacing with a b-Ga2O3 template layer. k-Ga2O3grown on sapphire has not been able to demonstrate its full potential due to materials imperfections created by strain induced by the lattice mismatch at the interface between the epilayer and the substrate. By adopting a b-Ga2O3 template on a c-sapphire substrate, higher quality k-Ga2O3thin films were obtained, as evidenced by a smoother surface morphology, narrower XRD peaks, and superior electrical performance. The implications of this phenomenon, caused by b-Ga2O3 buffer layer, are already very encouraging for both boosting current device performance and opening up the perspective of novel applications for Ga2O3. [reprint (PDF)]
19.	High-detectivity quantum-dot infrared photodetectors grown by metal-organic chemical-vapor deposition J. Szafraniec, S. Tsao, W. Zhang, H. Lim, M. Taguchi, A.A. Quivy, B. Movaghar and M. Razeghi Applied Physics Letters 88 (121102)-- March 20, 2006 ...[Visit Journal] A mid-wavelength infrared photodetector based on InGaAs quantum dots buried in an InGaP matrix and deposited on a GaAs substrate was demonstrated. Its photoresponse at T=77 K was measured to be around 4.7 μm with a cutoff at 5.5 μm. Due to the high peak responsivity of 1.2 A/W and low dark-current noise of the device, a specific peak detectivity of 1.1 x 10¹² cm·Hz^½·W⁻¹ was achieved at −0.9 V bias [reprint (PDF)]
19.	Room temperature quantum cascade lasers with 22% wall plug efficiency in continuous-wave operation F. Wang, S. Slivken, D. H. Wu, and M. Razeghi Optics Express Vol. 28, Issue 12, pp. 17532-17538-- June 8, 2020 ...[Visit Journal] We report the demonstration of quantum cascade lasers (QCLs) with improved eﬃciency emitting at a wavelength of 4.9 µm in pulsed and continuous-wave(CW)operation. Based on an established design and guided by simulation, the number of QCL-emitting stages is increased in order to realize a 29.3% wall plug eﬃciency (WPE) in pulsed operation at room temperature. With proper fabrication and packaging, a 5-mm-long, 8-µm-wide QCL with a buried ridge waveguide is capable of 22% CW WPE and 5.6 W CW output power at room temperature. This corresponds to an extremely high optical density at the output facet of ∼35 MW/cm², without any damage. [reprint (PDF)]
19.	Current status and potential of high power mid-infrared intersubband lasers S. Slivken, Y. Bai, B. Gokden, S.R. Darvish and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7608, p. 76080B-1-- January 22, 2010 ...[Visit Journal] Some of the recent advances in high power quantum cascade laser development will be reviewed in this paper. Research areas explored include short wavelength (λ <4 µm) lasers, high performance strain-balanced heterostructures, and high power long wavelength (7< λ< 16 µm) lasers. Near λ=4.5 µm, highlights include demonstration of 18% continuous wave wallplug efficiency at room temperature, 53% pulsed wallplug efficiency at 40 K, and 120 W of peak power output from a single device at room temperature. Near λ ~10 µm, up to 0.6 W of continuous output power at room temperature has also been demonstrated, with pulsed efficiencies up to 9%. [reprint (PDF)]
19.	Bias–selectable nBn dual–band long–/very long–wavelength infrared photodetectors based on InAs/InAsSb/AlAsSb type–II superlattices Abbas Haddadi, Arash Dehzangi, Romain Chevallier, Sourav Adhikary, & Manijeh Razeghi Nature Scientific Reports 7, Article number: 3379-- June 13, 2017 ...[Visit Journal] Type–II superlattices (T2SLs) are a class of artificial semiconductors that have demonstrated themselves as a viable candidate to compete with the state–of–the–art mercury–cadmium–telluride material system in the field of infrared detection and imaging. Within type–II superlattices, InAs/InAs_1−xSb_x T2SLs have been shown to have a significantly longer minority carrier lifetime. However, demonstration of high–performance dual–band photodetectors based on InAs/InAs_1−xSb_x T2SLs in the long and very long wavelength infrared (LWIR & VLWIR) regimes remains challenging. We report the demonstration of high–performance bias–selectable dual–band long–wavelength infrared photodetectors based on new InAs/InAsSb/AlAsSb type–II superlattice design. Our design uses two different bandgap absorption regions separated by an electron barrier that blocks the transport of majority carriers to reduce the dark current density of the device. As the applied bias is varied, the device exhibits well–defined cut–off wavelengths of either ∼8.7 or ∼12.5 μm at 77 K. This bias–selectable dual–band photodetector is compact, with no moving parts, and will open new opportunities for multi–spectral LWIR and VLWIR imaging and detection. [reprint (PDF)]
19.	High Thermal Stability of κ-Ga2O3 Grown by MOCVD Junhee Lee, Honghyuk Kim, Lakshay Gautam and Manijeh Razeghi Lee, J.; Kim, H.; Gautam, L.; Razeghi, M. High Thermal Stability of κ-Ga2O3 Grown by MOCVD. Crystals 2021, 11, 446. https://doi.org/ 10.3390/cryst11040446 ...[Visit Journal] We report a high thermal stability of kappa gallium oxide grown on c-plane sapphire substrate by metal organic chemical vapor deposition. Kappa gallium oxide is widely known as a metastable polymorph transitioning its phase when subjected to a high temperature. Here, we show the kappa gallium oxide whose phase is stable in a high temperature annealing process at 1000 °C. These oxide films were grown at 690 °C under nitrogen carrier gas. The materials showed high electrical resistivity when doped with silicon, whereas the film conductivity was significantly improved when doped with both indium and silicon. This work provides a pathway to overcoming limitations for the advance in utilizing kappa gallium oxide possessing superior electrical characteristics. [reprint (PDF)]
19.	III-Nitride Optoelectronic Devices: From Ultraviolet Toward Terahertz M. Razeghi IEEE Photonics Journal-Breakthroughs in Photonics 2010, Vol. 3, No. 2, p. 263-267-- April 26, 2011 ...[Visit Journal] We review III-Nitride optoelectronic device technologies with an emphasis on recent breakthroughs. We start with a brief summary of historical accomplishments and then report the state-of-the-art in three key spectral regimes: (1) Ultraviolet (AlGaN-based avalanche photodiodes, single photon detectors, focal plane arrays, and light emitting diodes), (2) Visible (InGaN-based solid state lighting, lasers, and solar cells), and (3) Near-, mid-infrared, and terahertz (AlGaN/GaN-based gap-engineered intersubband devices). We also describe future trends in III-Nitride optoelectronic devices. [reprint (PDF)]
19.	Surface plasmon enhanced light emission from AlGaN-based ultraviolet light-emitting diodes grown on Si (111) Chu-Young Cho, Yinjun Zhang, Erdem Cicek, Benjamin Rahnema, Yanbo Bai, Ryan McClintock, and Manijeh Razeghi Appl. Phys. Lett. 102, 211110 (2013)-- May 31, 2013 ...[Visit Journal] We report on the development of surface plasmon (SP) enhanced AlGaN-based multiple quantum wells (MQWs) ultraviolet (UV) light-emitting diodes (LEDs) grown on silicon (111) substrates. In order to generate SP-coupling with the radiating dipoles in MQWs, an aluminum layer is selectively deposited in holes etched in the top p-AlGaN to p-GaN layers. After flip-chip bonding and substrate removal, an optical output power of ∼1.2 mW is achieved at an emission wavelength of 346 nm; the output power of these UV LEDs with Al layer is increased by 45% compared to that of conventional UV LEDs without Al layer. This enhancement can be attributed to an increase in the spontaneous emission rate and improved internal quantum efficiency via resonance coupling between excitons in MQWs and SPs in the aluminum layer. [reprint (PDF)]
19.	Transport and photodetection in self-assembled semiconductor quantum dots M Razeghi, H Lim, S Tsao, J Szafraniec, W Zhang, K Mi and B Movaghar Nanotechnology 16 219-- January 7, 2005 ...[Visit Journal] A great step forward in science and technology was made when it was discovered that lattice mismatch can be used to grow highly ordered, artificial atom-like structures called self-assembled quantum dots. Several groups have in the meantime successfully demonstrated useful infrared photodetection devices which are based on this technology. The new physics is fascinating, and there is no doubt that many new applications will be found when we have developed a better understanding of the underlying physical processes, and in particular when we have learned how to integrate the exciting new developments made in nanoscopic addressing and molecular self-assembly methods with semiconducting dots. In this paper we examine the scientific and technical questions encountered in current state of the art infrared detector technology and suggest ways of overcoming these difficulties. Promoting simple physical pictures, we focus in particular on the problem of high temperature detector operation and discuss the origin of dark current, noise, and photoresponse. [reprint (PDF)]
19.	High-Power CW Mid-IR Quantum Cascade Lasers J.R. Meyer, W.W. Bewley, J.R. Lindle, I. Vurgaftman, A.J. Evans, J.S. Yu, S. Slivken, and M. Razeghi SPIE Conference, Jose, CA, -- January 22, 2005 ...[Visit Journal] We report the cw operation of quantum cascade lasers that do not require cryogenic cooling and emit at λ = 4.7-6.2 µm. At 200 K, more than 1 W of output power is obtained from 12-µm-wide stripes, with a wall-plug efficiency (η_wall) near 10%. Room-temperature cw operation has also been demonstrated, with a maximum output power of 640 mW (η_wall = 4.5%) at 6 µm and 260 mW (η_wall = 2.3%) at 4.8 µm. Far-field characterization indicates that whereas the beam quality remains close to the diffraction limit in all of the tested lasers, in the devices emitting at 6.2 µm the beam tends to steer by as much as 5-10° degrees in either direction with varying temperature and pump current. [reprint (PDF)]
19.	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)]
19.	Extended short wavelength infrared heterojunction phototransistors based on type II superlattices Arash Dehzangi , Ryan McClintock, Donghai Wu , Abbas Haddadi, Romain Chevallier , and Manijeh Razeghi Applied Physics Letters 114, 191109-- May 17, 2019 ...[Visit Journal] A two terminal extended short wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb on a GaSb substrate is designed, fabricated, and investigated. With the base thickness of 40 nm, the device exhibited a 100% cut-off wavelength of 2.3 λ at 300 K. The saturated peak responsivity value is 320.5 A/W at 300 K, under front-side illumination without any antireflection coating. A saturated optical gain of 245 at 300K was measured. At the same temperature, the device exhibited a collector dark current density (at unity optical gain) and a DC current gain of 7.8 X 10³ A/cm² and 1100, respectively. The device exhibited a saturated dark current shot noise limited specific detectivity of 4.9 X 10¹¹ cm·Hz^½/W at 300 K which remains constant over a broad range of wavelengths and applied biases. [reprint (PDF)]
19.	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 ...[Visit Journal] 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 (PDF)]
19.	Continuous-wave operation of λ ~ 4.8 µm quantum-cascade lasers at room temperature A. Evans, J.S. Yu, S. Slivken, and M. Razeghi Applied Physics Letters, 85 (12)-- September 20, 2004 ...[Visit Journal] Continuous-wave (cw) operation of quantum-cascade lasers emitting at λ~4.8 µm is reported up to a temperature of 323 K. Accurate control of layer thickness and strain-balanced material composition is demonstrated using x-ray diffraction. cw output power is reported to be in excess of 370 mW per facet at 293 K, and 38 mW per facet at 323 K. Room-temperature average power measurements are demonstrated with over 600 mW per facet at 50% duty cycle with over 300 mW still observed at 100% (cw) duty cycle. [reprint (PDF)]
19.	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 ...[Visit Journal] 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 (PDF)]
19.	GaInAs and GaInAsP materials grown by low pressure MOCVD for microwave and optoelectronic applications J.P. Duchemin, J.P. Hirtz, M. Razeghi, M. Bonnet , S.D. Hersee J.P. Duchemin, J.P. Hirtz, M. Razeghi, M. Bonnet, S.D. Hersee, GaInAs and GaInAsP materials grown by low pressure MOCVD for microwave and optoelectronic applications, Journal of Crystal Growth, Volume 55, Issue 1, 1981, Pages 64-73-- October 1, 1981 ...[Visit Journal] The low pressure MOCVD technique has been successfully used to grow GaInAsP, lattice-matched to InP, for the complete compositional range between InP (λ=0.91 μm) and the ternary compound Ga0.47In0.53As (λ=1.67 μm). By contrast to LPE growth it has been found that during the MOCVD growth of double heterostructures InP can be grown directly onto the ternary or quaternary with no disturbance of the active layer, i.e. there is no effect equivalent to “melt back”. The compositional grading on both sides of the active layer was measured by scanning Auger spectroscopy on bevelled samples. It was found that the graded regions were typically less than 100 Å wide for GaInAsP active layers and less than 50 Å wide for GaInAs active layers. Single layers of undoped GaInAs exhibited a typical mobility of 6700 cm2 V-1s-1 at 1.5×1017 cm-3. The compositional uniformity of the ternary layers was characterised by measurement of the photoluminescence wavelength at various points on a large sample. The wavelength varied by <3 nm over 95% of the area, which was approximately 8 cm2. Our early MOCVD grown GaInAsP/InP DH lasers exhibited high thresholds due to a poor interface between the p-InP and the active layer. However, recently fabricated broad area lasers emitting at 1.27 μm show an average threshold current density of 1.5 kA cm-2 with a T0 of between 70 to 80 K. Stripe geometry lasers have being fabricated from this material and CW operation has been obtained. [reprint (PDF)]
19.	Room temperature compact THz sources based on quantum cascade laser technology M. Razeghi; Q.Y. Lu; N. Bandyopadhyay; S. Slivken; Y. Bai Proc. SPIE 8846, Terahertz Emitters, Receivers, and Applications IV, 884602 (September 24, 2013)-- November 24, 2013 ...[Visit Journal] We present the high performance THz sources based on intracavity difference-frequency generation from mid-infrared quantum cascade lasers. Room temperature single-mode operation in a wide THz spectral range of 1-4.6 THz is demonstrated from our Čerenkov phase-matched THz sources with dual-period DFB gratings. High THz power up to 215 μW at 3.5 THz is demonstrated via epi-down mounting of our THz device. The rapid development renders this type of THz sources promising local oscillators for many astronomical and medical applications. [reprint (PDF)]
19.	Monolithic terahertz source Q. Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai and M. Razeghi Nature Photonics \| Research Highlights -- July 31, 2014 ...[Visit Journal] To date, the production of continuous-wave terahertz (THz) sources based on intracavity difference-frequency generation from mid-infrared quantum cascade lasers operating at room temperature has proved elusive. A critical problem is that, to achieve a large nonlinear susceptibility for frequency conversion, the active region of the quantum cascade laser requires high doping, which elevates the lasing threshold current density. Now, Quan-Yong Lu and colleagues from Northwestern University in the USA have overcome this problem and demonstrated a room-temperature continuous-wave THz source based on difference-frequency generation in quantum cascade lasers. They designed quantum-well structures based on In_0.53Ga_0.47As/In_0.52Al_0.48As material system for two mid-infrared wavelengths. The average doping in the active region was about 2.5 × 10¹⁶ cm⁻³. A buried ridge, buried composite distributed-feedback waveguide with the Čerenkov phase-matching scheme was used to reduce the waveguide loss and enhance heat dissipation. As a result, single-mode emission at 3.6 THz was observed at 293 K. The continuous-wave THz power reached 3 μW with a conversion efficiency of 0.44 mW W⁻² from mid-infrared to THz waves. Using a similar device design, a THz peak power of 1.4 mW was achieved in pulse mode. [reprint (PDF)]
19.	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 ...[Visit Journal] 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 (PDF)]
19.	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)]
19.	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)]
19.	High quantum efficiency mid-wavelength infrared type-II InAs/InAs_1-xSb_x superlattice photodiodes grown by metal-organic chemical vapor deposition Donghai Wu , Quentin Durlin, Arash Dehzangi , Yiyun Zhang , and Manijeh Razeghi Appl. Phys. Lett. 114, 011104-- January 8, 2019 ...[Visit Journal] We report the growth and characterization of mid-wavelength infrared type-II InAs/InAs_1-xSb_x superlattice photodiodes on GaSb substrates grown by metal-organic chemical vapor deposition. At 150 K, the 50% cut-off wavelength is 5.0 um, the dark current density is 3.3x10⁻⁴ A/cm² under −20mV bias, and the peak responsivity is 1.76A/W corresponding to a quantum efficiency of 55% without anti-reflection coating. A specific detectivity of 1.2x10¹¹cmHz^1/2/W is achieved at 4.0 um under −20mV bias at 150 K. [reprint (PDF)]
19.	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)]

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