Center for Quantum Devices - Journal Articles and Conference Proceedings

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401.	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 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
402.	High performance mid-wavelength quantum dot infrared photodetectors for focal plane arrays M. Razeghi, H. Lim, S. Tsao, M. Taguchi, W. Zhang and A.A. Quivy SPIE Conference, San Diego, CA, Vol. 6297, pp. 62970C-- August 13, 2006 Quantum dot infrared photodetectors (QDIPs) have recently emerged as promising candidates for detection in the middle wavelength infrared (MWIR) and long wavelength infrared (LWIR) ranges. Here, we report our recent results for mid-wavelength QDIPs grown by low-pressure metalorganic chemical vapor deposition. Three monolayer of In_0.68Ga_0.32As self-assembled via the Stranski-Krastanov growth mode and formed lens-shaped InGaAs quantum dots with a density around 3×10₁₀ cm^-2. The peak responsivity at 77 K was measured to be 3.4 A/W at a bias of -1.9 V with 4.7 µm peak detection wavelength. Focal plane arrays (FPAs) based on these devices have been developed. The preliminary result of FPA imaging is presented. reprint
403.	Reliability of strain-balanced Ga_0.331In_0.669As/Al_0.659In_0.341As/InP quantum-cascade lasers under continuous-wave room-temperature operation A. Evans and M. Razeghi Applied Physics Letters, 88 (26)-- June 26, 2006 Constant current aging is reported for two randomly selected high-reflectivity-coated QCLs with an output power over 100 mW. QCLs are tested under continuous-wave operation at a heat sink temperature of 298 K(25 °C) corresponding to an internal temperature of 378 K (105 °C). Over 4000 h of continuous testing is reported without any decrease in output power. reprint
404.	Temperature dependent characteristics of λ ~ 3.8 µm room-temperature continuous-wave quantum-cascade lasers J.S. Yu, A. Evans, S. Slivken, S.R. Darvish and M. Razeghi Applied Physics Letters, 88 (25)-- June 19, 2006 The highest-performance device displays pulsed laser action at wavelengths between 3.4 and 3.6 μm, for temperatures up to 300 K, with a low temperature (80 K) threshold current density of approximately 2.6 kA/cm², and a characteristic temperature of T₀~130 K. The shortest wavelength QCL (λ ~ 3.05 μm) has a higher threshold current density (~12 kA/cm² at T=20 K) and operates in pulsed mode at temperatures up to 110 K. reprint
405.	Quantum Dots in GaInP/GaInAs/GaAs for Infrared Sensing M. Razeghi, H. Lim, S. Tsao, M. Taguchi, W. Zhang, and A.A. Quivy Advances in Science and Technology 51-- June 4, 2006 Quantum dots grown by epitaxial self-assembly via Stranski- Krastanov growth mode have many favorable properties for infrared sensing. Because of their very small size and three-dimensional confinement, the electronic energy levels are quantized and discrete. These quantum effects lead to a unique property, “phonon bottleneck”, which might enable the high operating temperature of infrared sensing which usually requires cryogenic cooling. Here we report a focal plane array (FPA) based on an epitaxial self-assembled quantum dot infrared detector (QDIP). The device structure containing self-assembled In_0.68Ga_0.32As quantum dots with a density around 3×10¹⁰ cm^-2 was grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). Using different structures, we successfully developed QDIPs with a peak photoresponse around 5 μm and 9 μm. High peak detectivities were achieved at 77 K from both QDIPs. By stacking both device structures, we demonstrated a two-color QDIP whose peak detection wavelength could be tuned from 5 μm to 9 μm by changing the bias. 256×256 detector arrays based on 5 μm and 9 μm-QDIPs were fabricated with standard photolithography, dry etching and hybridization to a read-out integrated circuit (ROIC). We demonstrated thermal imaging from our FPAs based on QDIPs.
406.	Room-temperature, high-power and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ ~ 9.6 µm S.R. Darvish, S. Slivken, A. Evans, J.S. Yu, and M. Razeghi Applied Physics Letters, 88 (20)-- May 15, 2006 High-power continuous-wave (cw) operation of distributed-feedback quantum-cascade lasers is reported. Continuous-wave output powers of 100 mW at 25 °C and 20 mW at 50 °C are obtained. The device exhibits a cw threshold current density of 1.34 kA/cm², a maximum cw wall-plug efficiency of 1% at 25 °C, and a characteristic temperature of ~190 K in pulsed mode. Single-mode emission near 9.6 μm with a side-mode suppression ratio of ≥ 30 dB and a tuning range of 2.89 cm^–1 from 15 to 50 °C is obtained. reprint
407.	Type-II superlattice photodetectors for MWIR to VLWIR focal plane arrays M. Razeghi, Y. Wei, A. Hood, D. Hoffman, B.M. Nguyen, P.Y. Delaunay, E. Michel and R. McClintock SPIE Infrared Technology and Applications Conference, April 17-21, 2006, Orlando, FL Proceedings – Infrared Technology and Applications XXXII, Vol. 6206, p. 62060N-1-- April 21, 2006 Results obtained on GaSb/InAs Type-II superlattices have shown performance comparable to HgCdTe detectors, with the promise of higher performance due to reduced Auger recombination and dark current through improvements in device design and material quality. In this paper, we discuss advancements in Type-II IR sensors that cover the 3 to > 30 µm wavelength range. Specific topics covered will be device design and modeling using the Empirical Tight Binding Method (ETBM), material growth and characterization, device fabrication and testing, as well as focal plane array processing and imaging. Imaging has been demonstrated at room temperature for the first time with a 5 µm cutoff wavelength 256×256 focal plane array. reprint
408.	Quantum-dot infrared photodetectors and focal plane arrays M. Razeghi, H. Lim, S. Tsao, M. Taguchi, W. Zhang, and A.A. Quivy SPIE Infrared Technology and Applications Conference, April 17-21, 2006, Orlando, FL Proceedings – Infrared Technology and Applications XXXII, Vol. 6206, p. 62060I-1-- April 21, 2006 We report our recent results about mid-wavelength infrared quantum-dot infrared photodetectors (QDIPs) grown by low-pressure metalorganic chemical vapor deposition. A very high responsivity and a very low dark current were obtained. A high peak detectivity of the order of 3×10¹² Jones was achieved at 77 K. The temperature dependent device performance was also investigated. The improved temperature insensitivity compared to QWIPs was attributed to the properties of quantum dots. The device showed a background limited performance temperature of 220 K with a 45° field of view and 300K background. reprint
409.	Electroluminescence at 375 nm from a Zn0/GaN:Mg/c-Al₂O₃ heterojunction light emitting diodes D.J. Rogers, F.Hosseini Teherani, A. Yasan, K. Minder, P. Kung, and M. Razeghi Applied Physics Letters, 88 (14)-- April 13, 2006 n-ZnO/p-GaN:Mg heterojunction light emitting diode (LED) mesas were fabricated on c-Al₂O₃ substrates using pulsed laser deposition for the ZnO and metal organic chemical vapor deposition for the GaN:Mg. Room temperature (RT) photoluminescence (PL) showed an intense main peak at 375 nm and a negligibly low green emission indicative of a near band edge excitonic emission from a ZnO layer with low dislocation/defect density. The LEDs showed I-V characteristics confirming a rectifying diode behavior and a RT electroluminescence (EL) peaked at about 375 nm. reprint
410.	Improved performance of quantum cascade lasers through a scalable, manufacturable epitaxial-side-down mounting process A. Tsekoun, R. Go, M. Pushkarsky, M. Razeghi, and C. Kumar N. Patel Proceedings of the National Academy of Sciences 103 (13)-- March 26, 2006 We report substantially improved performance of high-power quantum cascade lasers (QCLs) by using epitaxial-side-down mounting that provides superior heat dissipation properties. We used aluminum nitride as the heatsink material and gold–tin eutectic solder. We have obtained continuous wave power output of 450 mW at 20°C from mid-IR QCLs. The improved thermal management achieved with epitaxial-side-down mounting combined with a highly manufacturable and scalable assembly process should permit incorporation of mid-IR QCLs in reliable instrumentation.
411.	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 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
412.	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 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
413.	High-power λ ~ 9.5 µm quantum-cascade lasers operating above room temperature in continuous-wave mode J.S. Yu, S. Slivken, A. Evans, S.R. Darvish, J. Nguyen, and M. Razeghi Applied Physics Letters, 88 (9)-- February 27, 2006 We report high-power continuous-wave (cw) operation of λ~9.5 μm quantum-cascade lasers to a temperature of 318 K. A high-reflectivity-coated 19-μm-wide and 3-mm-long device exhibits cw output powers as high as 150 mW at 288 K and still 22 mW at 318 K. In cw operation at 298 K, a threshold current density of 1.57 kA/cm², a slope efficiency of 391 mW/A, and a maximum wall-plug efficiency of 0.71% are obtained. reprint
414.	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 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
415.	Non-equilibrium radiation of long wavelength InAs/GaSb superlattice photodiodes D. Hoffman, A. Hood, F. Fuchs and M. Razeghi Journal of Applied Physics 99-- February 15, 2006 The emission behavior of binary-binary type-II InAs/GaSb superlattice photodiodes has been studied in the spectral range between 8 and 13 μm. With a radiometric calibration of the experimental setup the internal and external quantum efficiencies have been determined in the temperature range between 80 and 300 K for both the negative and positive luminescences. reprint
416.	Capacitance-voltage investigation of high purity InAs/GaSb superlattice photodiodes A. Hood, D. Hoffman, Y. Wei, F. Fuchs, and M. Razeghi Applied Physics Letters 88 (6)-- February 6, 2006 The residual carrier backgrounds of binary type-II InAs/GaSb superlattice photodiodes with cutoff wavelengths around 5 μm have been studied in the temperature range between 20 and 200 K. By applying a capacitance-voltage measurement technique, a residual background concentration below 10¹⁵ cm^–3 has been found. reprint
417.	Electroluminescence of InAs/GaSb heterodiodes D. Hoffman, A. Hood, E. Michel, F. Fuchs, and M. Razeghi IEEE Journal of Quantum Electronics, 42 (2)-- February 1, 2006 The electroluminescence of a Type-II InAs-GaSb superlattice heterodiode has been studied as a function of injection current and temperature in the spectral range between 3 and 13 μm. The heterodiode comprises a Be-doped midwavelength infrared (MWIR) superlattice with an effective bandgap around 270 meV and an undoped long wavelength infrared (LWIR) superlattice with an effective bandgap of 115 meV. reprint
418.	Quantum-Cascade Lasers Operating in Continuous-Wave Mode Above 90°C at λ ~5.25 µm A. Evans, J. Nguyen, S. Slivken, J.S. Yu, S.R. Darvish, and M. Razeghi Applied Physics Letters 88 (5)-- January 30, 2006 We report on the design and fabrication of λ~5.25 μm quantum-cascade lasers (QCLs) for very high temperature continuous-wave (CW) operation. CW operation is reported up to a maximum temperature of 90 °C (363 K). CW output power is reported in excess of 500 mW near room temperature with a low threshold current density. A finite element thermal model is used to investigate the G_th and maximum CW operating temperature of the QCLs. reprint
419.	Room-temperature continuous-wave operation of quantum-cascade lasers at λ ~ 4 µm J.S. Yu, S.R. Darvish, A. Evans, J. Nguyen, S. Slivken, and M. Razeghi Applied Physics Letters 88 (4)-- January 23, 2006 High-power cw λ~4 μm quantum-cascade lasers (QCLs) are demonstrated. The effect of different cavity length and laser die bonding is also investigated. For a high-reflectivity-coated 11-μm-wide and 4-mm-long epilayer-down bonded QCL, cw output powers as high as 1.6 W at 80 K and 160 mW at 298 K are obtained, and the cw operation is achieved up to 313 K with 12 mW. reprint
420.	Positive and negative luminescence in binary Type-II InAs/GaSb superlattice photodiodes D. Hoffman and M. Razeghi SPIE Conference, San Jose, CA, Vol. 6127, pp. 61271H-- January 23, 2006 In the present work, we show measurements of both positive and negative luminescence of binary Type-II InAs/GaSb superlattice photodiodes in the 3 to 13 μm spectral range. Through a radiometric calibration technique, we demonstrate temperature independent negative luminescence efficiencies of 45 % in the midwavelength (MWIR) sample from 220 K to 320 K without anti-reflective coating and values reaching 35 % in the long wavelength infrared (LWIR) spectrum sample. reprint
421.	Solar-blind avalanche photodiodes R. McClintock, K. Minder, A. Yasan, C. Bayram, F. Fuchs, P. Kung and M. Razeghi SPIE Conference, San Jose, CA, Vol. 6127, pp. 61271D-- January 23, 2006 There is a need for semiconductor based UV photodetectors to support avalanche gain in order to realize better performance and more effectively compete with existing photomultiplier tubes. However, there are numerous technical issues associated with the realization of high-quality solar-blind avalanche photodiodes (APDs). In this paper, APDs operating at 280 nm, within the solar-blind region of the ultraviolet spectrum, are investigated. reprint
422.	Performance characteristics of high-purity mid-wave and long-wave infrared type-II InAs/GaSb superlattice infrared photodiodes A. Hood, M. Razeghi, V. Nathan and M.Z. Tidrow SPIE Conference, San Jose, CA, Vol. 6127, pp. 61270U-- January 23, 2006 The authors report on recent advances in the development of mid-, long-, and very long-wavelength infrared (MWIR, LWIR, and VLWIR) Type-II InAs/GaSb superlattice infrared photodiodes. The residual carrier background of binary Type-II InAs/GaSb superlattice photodiodes of cut-off wavelengths around 5 µm has been studied in the temperature range between 10 and 200 K. A four-point, capacitance-voltage technique on mid-wavelength and long-wavelength Type-II InAs/GaSb superlattice infrared photodiodes reveal residual background concentrations around 5×10¹⁴ cm^-3. Additionally, recent progress towards LWIR photodiodes for focal plane array imaging applications is presented. reprint
423.	InGaAs/InGaP Quantum-Dot Photodetector with a High Detectivity H. Lim, S. Tsao, M. Taguchi, W. Zhang, A. Quivy and M. Razeghi SPIE Conference, San Jose, CA, Vol. 6127, pp. 61270N-- January 23, 2006 Quantum-dot infrared photodetectors (QDIPs) have recently been considered as strong candidates for numerous applications such as night vision, space communication, gas analysis and medical diagnosis involving middle and long wavelength infrared (MWIR and LWIR respectively) operation. This is due to their unique properties arising from their 3-dimensional confinement potential that provides a discrete density of states. They are expected to outperform quantum-well infrared photodetectors (QWIPs) as a consequence of their natural sensitivity to normal incident radiation, their higher responsivity and their higher-temperature operation. So far, most of the QDIPs reported in the literature were based on the InAs/GaAs system and were grown by molecular beam epitaxy (MBE). Here, we report on the growth of a high detectivity InGaAs/InGaP QDIP grown on a GaAs substrate using low-pressure metalorganic chemical vapor deposition (MOCVD). reprint
424.	InAs quantum dot infrared photodetectors on InP by MOCVD W. Zhang, H. Lim, M. Taguchi, A. Quivy and M. Razeghi SPIE Conference, San Jose, CA, Vol. 6127, pp. 61270M -- January 23, 2006 We report our recent results of InAs quantum dots grown on InP substrate by low-pressure metalorganic chemical vapor deposition (MOCVD) for the application of quantum dot infrared photodetector (QDIP). We have previously demonstrated the first InP-based QDIP with a peak detection wavelength at 6.4 µm and a detectivity of 10¹⁰ cm·Hz^½/W at 77K. Here we show our recent work toward shifting the detection wavelength to the 3-5 µm middlewavelength infrared (MWIR) range. The dependence of the quantum dot on the growth conditions is studied by atomic force microscopy, photoluminescence and Fourier transform infrared spectroscopy. Possible ways to increase the quantum efficiency of QDIPs are discussed. reprint
425.	Fabrication of GaN nanotubular material using MOCVD with aluminum oxide membrane W.G. Jung, S.H. Jung, P. Kung, and M. Razeghi SPIE Conference, San Jose, CA, Vol. 6127, pp. 61270K-- January 23, 2006 GaN nanotubular material is fabricated with aluminum oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminum oxide membrane with ordered nano holes is used as template. Gallium nitride is deposited at the inner wall of the nano holes in aluminum oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis condition in MOCVD is obtained successfully for the gallium nitride nanotubular material in this research. The diameter of GaN nanotube fabricated is approximately 200 ~ 250 nm and the wall thickness is about 40 ~ 50 nm. GaN nanotubular material consists of numerous fine GaN particulates with sizes ranging 15 to 30 nm. reprint

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