Center for Quantum Devices - Most Downloaded Journal Articles

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2.	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)]
2.	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)]
2.	320x256 Solar-Blind Focal Plane Arrays based on Al_xGa_1-xN R. McClintock, K. Mayes, A. Yasan, D. Shiell, P. Kung, and M. Razeghi Applied Physics Letters, 86 (1)-- January 3, 2005 ...[Visit Journal] We report AlGaN-based back-illuminated solar-blind ultraviolet focal plane arrays operating at a wavelength of 280 nm. The electrical characteristics of the individual pixels are discussed, and the uniformity of the array is presented. The p–i–n photodiode array was hybridized to a 320×256 read-out integrated circuit entirely within our university research lab, and a working 320×256 camera was demonstrated. Several example solar-blind images from the camera are also provided. [reprint (PDF)]
2.	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)]
2.	High-Performance InP-Based Mid-IR Quantum Cascade Lasers M. Razeghi IEEE Journal of Selected Topics in Quantum Electronics, Vol. 15, No. 3, May-June 2009, p. 941-951.-- June 5, 2009 ...[Visit Journal] Quantum cascade lasers (QCLs) were once considered as inefficient devices, as the wall-plug efficiency (WPE) was merely a few percent at room temperature. But this situation has changed in the past few years, as dramatic enhancements to the output power andWPE have been made for InP-based mid-IR QCLs. Room temperature continuous-wave (CW) output power as high as 2.8 W and WPE as high as 15% have now been demonstrated for individual devices. Along with the fundamental exploration of refining the design and improving the material quality, a consistent determination of important device performance parameters allows for strategically addressing each component that can be improved potentially. In this paper, we present quantitative experimental evidence backing up the strategies we have adopted to improve the WPE for QCLs with room temperature CW operation. [reprint (PDF)]
2.	Transport properties in n-type InSb films grown by metalorganic chemical vapor deposition S.N. Song, J.B. Ketterson, Y.H. Choi, R. Sudharsanan, and M. Razeghi Applied Physics Letters 63 (7)-- August 16, 1993 ...[Visit Journal] We have measured the temperature and magnetic field dependence of the Hall mobility and transverse magnetoresistance in n-type InSb films epitaxially grown on GaAs substrates by metalorganic chemical vapor deposition. The films show a giant magnetoresistance: e.g., at 240 K the resistivity increases over 20 times at a magnetic field of 5 T; the low field coefficient of resistivity at 77 K is as high as 47.5 μ·Ω· cm/G. The Hall mobility decreases with magnetic field and saturates at higher fields. By taking the interface carrier transport into account, the observed field dependence of the Hall mobility and magnetoresistance may be understood based on a two-layer model. [reprint (PDF)]
2.	Overview of Quantum Cascade Laser Research at the Center for Quantum Devices S. Slivken, A. Evans, J. Nguyen, Y. Bai, P. Sung, S.R. Darvish, W. Zhang and M. Razeghi SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 69000B-1-8.-- February 1, 2008 ...[Visit Journal] Over the past several years, our group has endeavored to develop high power quantum cascade lasers for a variety of remote and high sensitivity infrared applications. The systematic optimization of laser performance has allowed for demonstration of high power, continuous-wave quantum cascade lasers operating above room temperature. In the past year alone, the efficiency and power of our short wavelength lasers (~4.8 µm) has doubled. In continuous wave at room temperature, we have now separately demonstrated ~10% wallplug efficiency and ~700 mW of output power. Up to now, we have been able to show that room temperature continuous wave operation with > 100 mW output power in the 3.8 < λ < 11.5 µm wavelength range is possible. [reprint (PDF)]
2.	Gain and recombination dynamics of quantum-dot infrared photodetectors H. Lim, B. Movaghar, S. Tsao, M. Taguchi, W. Zhang, A.A. Quivy, and M. Razeghi Physical Review B, 74 (20)-- November 15, 2006 ...[Visit Journal] In this paper we present a theory of diffusion and recombination in QDIPs which is an attempt to explain the recently reported values of gain in these devices. We allow the kinetics to encompass both the diffusion and capture rate limited regimes of carrier relaxation using rigorous random walk and diffusion methods. The photoconductive gains are calculated and compared with the experimental values obtained from InGaAs/InGaP/GaAs and InAs/InP QDIPs using the generation-recombination noise analysis. [reprint (PDF)]
2.	Quantum Devices Based on Modern Band Structure Engineering and Epitaxial Technology M. Razeghi Modern Physics Letters B, Vol. 22, No. 24, p. 2343-2371-- September 20, 2008 ...[Visit Journal] Modern band structure engineering is based both on the important discoveries of the past century and modern epitaxial technology. The general goal is to control the behavior of charge carriers on an atomic scale, which affects how they interact with each other and their environment. Starting from the basic semiconductor heterostructure, band structure engineering has evolved into a powerful discipline, employing lower dimensionality to demonstrate new material properties. Several modern technologies under development are used as examples of how this discipline is enabling new types of devices and new functionality in areas with immediate application.
2.	High Power, Room Temperature, Continuous-Wave Operation of Quantum Cascade Lasers Grown by GasMBE A. Evans, J. David, L. Doris, J.S. Yu, S. Slivken and M. Razeghi SPIE Conference, Jose, CA, Vol. 5359, pp. 188-- January 25, 2004 ...[Visit Journal] Very high power continuous-wave quantum cascade lasers are demonstrated in the mid-infrared (3 - 6 µm) wavelength range. λ~6 µm high-reflectivity coated QCLs are demonstrated producing over 370 mW continuous-wave power at room temperature with continuous-wave operation up to 333 K. Advanced heterostructure geometries, including the use of a thick electroplated gold, epilayer-side heat sink and a buried-ridge heterostructure are demonstrated to improve laser performance significantly when combined with narrow laser ridges. Recent significant improvements in CW operation are presented and include the development if narrow (9 µm-wide) ridges for high temperature CW operation. GasMBE growth of the strain-balanced λ~6 µm QCL heterostructure is discussed. X-ray diffraction measurements are presented and compared to computer simulations that indicate excellent layer and compositional uniformity of the structure. [reprint (PDF)]
2.	Investigation of impurities in type-II InAs/GaSb superlattices via capacitance-voltage measurement G. Chen, A. M. Hoang, S. Bogdanov, A. Haddadi, P. R. Bijjam, B.-M. Nguyen, and M. Razeghi Applied Physics Letters 103, 033512 (2013)-- July 17, 2013 ...[Visit Journal] Capacitance-voltage measurement was utilized to characterize impurities in the non-intentionally doped region of Type-II InAs/GaSb superlattice p-i-n photodiodes. Ionized carrier concentration versus temperature dependence revealed the presence of a kind of defects with activation energy below 6 meV and a total concentration of low 10¹⁵ cm⁻³. Correlation between defect characteristics and superlattice designs was studied. The defects exhibited a p-type behavior with decreasing activation energy as the InAs thickness increased from 7 to 11 monolayers, while maintaining the GaSb thickness of 7 monolayers. With 13 monolayers of InAs, the superlattice became n-type and the activation energy deviated from the p-type trend. [reprint (PDF)]
2.	Long-Wavelength Infrared Photodetectors Based on InSbBi Grown on GaAs Substrates J.J. Lee, J.D. Kim, and M. Razeghi Applied Physics Letters 71 (16)-- October 20, 1997 ...[Visit Journal] We demonstrate the operation of InSbBi infrared photoconductive detectors grown by low-pressure metalorganic chemical vapor deposition on semi-insulating GaAs substrates. The fabricated photodetector showed a cutoff wavelength of 7.7 μm at 77 K. The responsivity of the InSbBi photodetector at 7 μm was about 3.2 V/W at 77 K. The corresponding Johnson-noise limited detectivity was 4.7×10⁸ cm· Hz^½/W. The carrier lifetime was estimated to be about 86 ns from the voltage-dependent responsivity measurements. [reprint (PDF)]
2.	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)]
2.	Stability of far fields in double heterostructure and multiple quantum well InAsSb/InPAsSb/InAs midinfrared lasers H. Yi, A. Rybaltowski, J. Diaz, D. Wu, B. Lane, Y. Xiao, and M. Razeghi Applied Physics Letters 70 (24)-- June 16, 1997 ...[Visit Journal] Far fields in perpendicular direction to the junction are investigated in double heterostructure (DH) and multiple quantum well (MQW) midwave-infrared InAsSb/InPAsSb/InAs lasers (λ = 3.2–3.6 μm). Strong broadening of the far fields in the DH lasers was observed with increases in temperature and/or current. On the contrary, MQW lasers with otherwise identical structure exhibit very stable far fields as narrow as 23° for all the operating conditions investigated. Our experiment and theoretical modeling suggest that these different behaviors of far fields in DH and MQW lasers are attributed to the refractive index fluctuation in the InAsSb laser active region. [reprint (PDF)]
2.	The importance of band alignment in VLWIR type-II InAs/GaSb heterodiodes containing the M-structure barrier D. Hoffman, B.M. Nguyen, E.K. Huang, P.Y. Delaunay, S. Bogdanov, P. Manukar, M. Razeghi, and V. Nathan SPIE Proceedings, San Jose, CA Volume 7222-15-- January 26, 2009 ...[Visit Journal] The Type-II InAs/GaSb superlattice photon detector is an attractive alternative to HgCdTe photodiodes and QWIPS. The use of p+ - pi - M - N+ heterodiode allows for greater flexibility in enhancing the device performance. The utilization of the Empirical Tight Binding method gives the band structure of the InAs/GaSb superlattice and the new M- structure (InAs/GaSb/AlSb/GaSb) superlattice allowing for the band alignment between the binary superlattice and the M- superlattice to be determined and see how it affects the optical performance. Then by modifying the doping level of the M- superlattice an optimal level can be determined to achieve high detectivity, by simultaneously improving both photo-response and reducing dark current for devices with cutoffs greater than 14.5 µm. [reprint (PDF)]
2.	High performance antimony based type-II superlattice photodiodes on GaAs substrates B.M. Nguyen, D. Hoffman, E.K. Huang, P.Y. Delaunay, and M. Razeghi SPIE Porceedings, Vol. 7298, Orlando, FL 2009, p. 72981T-- April 13, 2009 ...[Visit Journal] In recent years, Type-II InAs/GaSb superlattices grown on GaSb substrate have achieved significant advances in both structural design and material growth, making Type-II superlattice infrared detector a rival competitor to the state-of-the-art MCT technology. However, the limited size and strong infrared absorption of GaSb substrates prevent large format type-II superlattice infrared imagers from being realized. In this work, we demonstrate type-II superlattices grown on GaAs substrates, which is a significant step toward third generation infrared imaging at low cost. The device performances of Type-II superalttice photodetectors grown on these two substrates are compared. [reprint (PDF)]
2.	High quantum efficiency two color type-II InAs/GaSb n-i-p-p-i-n photodiodes P.Y. Delaunay, B.M. Nguyen, D. Hoffman, A. Hood, E.K. Huang, M. Razeghi, and M.Z. Tidrow Applied Physics Letters, Vol. 92, No. 11, p. 111112-1-- March 17, 2008 ...[Visit Journal] A n-i-p-p-i-n photodiode based on type-II InAs/GaSb superlattice was grown on a GaSb substrate. The two channels, with respective 50% of responsivity cutoff wavelengths at 7.7 and 10 µm, presented quantum efficiencies (QEs) of 47% and 39% at 77 K. The devices can be operated as two diodes for simultaneous detection or as a single n-i-p-p-i-n detector for sequential detection. In the latter configuration, the QEs at 5.3 and 8.5 µm were measured as high as 40% and 39% at 77 K. The optical cross-talk between the two channels could be reduced from 0.36 to 0.08 by applying a 50 mV bias. [reprint (PDF)]
2.	Development of material quality and structural design for high performance type-II InAs/GaSb superlattice photodiodes and focal plane arrays M. Razeghi, B.M. Nguyen, D. Hoffman, P.Y. Delaunay, E.K. Huang, M.Z. Tidrow and V. Nathan SPIE Porceedings, Vol. 7082, San Diego, CA 2008, p. 708204-- August 11, 2008 ...[Visit Journal] Recent progress made in the structure design, growth and processing of Type-II InAs/GaSb superlattice photo-detectors lifted both the quantum efficiency and the R0A product of the detectors. Type-II superlattice demonstrated its ability to perform imaging in the Mid-Wave Infrared (MWIR)and Long-Wave Infrared (LWIR) ranges, becoming a potential competitor for technologies such as Quantum Well Infrared Photo-detectors (QWIP) and Mercury Cadmium Telluride (MCT). Using an empirical tight-binding model, we developed superlattices designs that were nearly lattice-matched to the GaSb substrates and presented cutoff wavelengths of 5 and 11 μm. We demonstrated high quality material growth with X-ray FWHM below 30 arcsec and an AFM rms roughness of 1.5 Å over an area of 20x20 μm2. The detectors with a 5 μm cutoff, capable of operating at room temperature, showed a R0A of 1.25 106 Ω.cm2 at 77K, and a quantum efficiency of 32%. In the long wavelength infrared, we demonstrated high quantum efficiencies above 50% with high R0A products of 12 Ω.cm2 by increasing the thickness of the active region. Using the novel M-structure superlattice design, more than one order of magnitude improvement has been observed for electrical performance of the devices. Focal plane arrays in the middle and long infrared range, hybridized to an Indigo read out integrated circuit, exhibited high quality imaging. [reprint (PDF)]
2.	Future of Al_xGa_1-xN Materials and Device Technology for Ultraviolet Photodetectors P. Kung, A. Yasan, R. McClintock, S. Darvish, K. Mi, and M. Razeghi SPIE Conference, San Jose, CA, Vol. 4650, pp. 199-- May 1, 2002 ...[Visit Journal] Design of the photodetector structure is one of the key issues in obtaining high performance devices; especially the thickness of the intrinsic region for p-i-n photodiodes is a crucial value and needs to be optimized. We compare the performance of the p-i-n photodiodes with different widths for the depletion region, which shows a trade-off between speed and responsivity of the devices. [reprint (PDF)]
2.	Gain and recombination dynamics in photodetectors made with quantum nanostructures: the quantum dot in a well and the quantum well B. Movaghar, S. Tsao, S. Abdollahi Pour, T. Yamanaka, and M. Razeghi Virtual Journal of Nanoscale Science & Technology, Vol. 18, No. 14-- October 6, 2008 ...[Visit Journal][reprint (PDF)]
2.	The correlation between x-ray diffraction patterns and strain distribution inside GaInP/GaAs superlattices X.G. He, M. Erdtmann, R. Williams, S. Kim, and M. Razeghi Applied Physics Letters 65 (22)-- November 28, 1994 ...[Visit Journal] Strong correlation between x‐ray diffraction characteristics and strain distribution inside GaInP/GaAs superlattices has been reported. It is found that the symmetry of (002) diffraction patterns can be used to evaluate the interface strain status. A sample with no interfacial strains has a symmetric (002) diffraction pattern and weak (004) diffraction pattern. It is also demonstrated that strain distribution in superlattices can be readily estimated qualitatively by analyzing x-ray diffraction patterns. [reprint (PDF)]
2.	Two-dimensional magnetophonon resonance in GaInAs-InP and GaInAs-AlInAs heterojunctions and superlattices J.C. Portal, G. Gregoris a b , M.A. Brummell , R.J. Nicholas, M. Razeghi, M.A. Di Forte-Poisson, K.Y. Cheng, A.Y. Cho J.C. Portal, G. Gregoris, M.A. Brummell, R.J. Nicholas, M. Razeghi, M.A. Di Forte-Poisson, K.Y. Cheng, A.Y. Cho, Two-dimensional magnetophonon resonance in GaInAs-InP and GaInAs-AlInAs heterojunctions and superlattices, Surface Science, Volume 142, Issues 1–3, 1984, Pages 368-374,-- July 1, 1984 ...[Visit Journal] We report the observation of magnetophonon resonance in GaInAs-InP heterojunctions and measurements of the temperature dependence of the oscillations. A single series of oscillations due to scattering by the “GaAs-like” mode of GaInAs is seen, in contrast to GaInAs-InP superlattices, where scattering from InP phonons is also observed, and GaInAs-AlInAs heterojunctions, where coupling to “InAs-like” modes only is seen. This behaviour is discussed in terms of long-range phonon interactions and interface phonons. [reprint (PDF)]
2.	GalnAs 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, GaInAs and GaInAsP materials grown by low pressure MOCVD for microwave and optoelectronic applications, Journal of Crystal Growth, 55, 1, 1981, Pages 64-73,-- August 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)]
2.	New frontiers in InP based quantum devices Manijeh Razeghi Indium Phosphide and Related Materials, 2008. IPRM 2008. 20th International Conference on, pp.1,4, (2008)-- May 29, 2008 ...[Visit Journal] Recent research activities taking place at center for quantum devices (CQD) based on InP material system, especially the exploration and demonstration of the state-of-art high performance quantum cascade lasers (QCL), greatly facilitate the understanding of the underlining physical principles governing the device operation. Thanks to the endless effort putting into the semiconductor epitaxy technologies, including the Molecular Beam Epitaxy (MBE) and low pressure metal organic chemical vapor deposition (LP-MOCVD), the world has seen a close approaching to the ultimate band gap engineering. Highly sophisticated man-made heterostructure, which incorporates hundreds of alternating layers of GaInAs/AlInAs with each layer thickness and composition specifically designed, can be created within a single growth. The material quality is evidenced by the atomically abrupt interfaces. The versatility of the band gap engineering is greatly enhanced by the strain-balanced technique, which allows for growing structures with continuously tunable conduction band offset with little defects. As a result, the room temperature continuous wave (CW) wall plug efficiency (WPE) and the maximum achievable output optical power from a single device have been constantly improving. Novel waveguide incorporating the photonic crystal distributed feedback (PCDFB) mechanism is also investigated with satisfactory preliminary results. [reprint (PDF)]
2.	Polarity inversion of Type-II InAs/GaSb superlattice photodiodes B.M. Nguyen, D. Hoffman, P.Y. Delaunay, M. Razeghi and V. Nathan Applied Physics Letters, Vol. 91, No. 10, p. 103503-1-- September 3, 2007 ...[Visit Journal] The authors demonstrated the realization of p-on-n Type-II InAs/GaSb superlattice photodiodes. Growth condition for high quality InAsSb layer lattice matched to GaSb was established for the use of an effective n-contact layer. By studying the effect of various GaSb capping layer thicknesses on the optical and electrical performances, an optimized thickness of 160 nm was determined. In comparison to as grown n-on-p superlattice photodiodes, this inverted design of p on n has shown similar quality. Finally, by analyzing Fabry-Perot interference fringes in the front side illuminated spectral measurement, the refractive index of the superlattice was determined to be approximately 3.8. [reprint (PDF)]

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