Center for Quantum Devices - Most Downloaded Journal Articles

Page 19 of 30: Prev << 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 >> Next (738 Items)

14.	High Power 3-12 μm Infrared Lasers: Recent Improvements and Future Trends M. Razeghi, S. Slivken, A. Tahraoui, A. Matlis, and Y.S. Park Physica E: Low-Dimensional Systems and Nanostructures 11 (2-3)-- October 1, 2001 ...[Visit Journal] In this paper, we discuss the progress of quantum cascade lasers (QCLs) grown by gas-source molecular beam epitaxy. Room temperature QCL operation has been reported for lasers emitting between 5-11 μm, with 9-11 μm lasers operating up to 425 K. Laser technology for the 3-5 μm range takes advantage of a strain-balanced active layer design. We also demonstrate record room temperature peak output powers at 9 and 11 μm (2.5 and 1 W, respectively) as well as record low 80K threshold current densities (250 A/cm²) for some laser designs. Preliminary distributed feedback (DFB) results are also presented and exhibit single mode operation for 9 μm lasers at room temperature. [reprint (PDF)]
14.	Ridge-Width Dependence on High-Temperature Continuous-Wave Quantum-Cascade Laser Operation S. Slivken, J.S. Yu, A. Evans, L. Doris, J. David, and M. Razeghi IEEE Photonics Technology Letters, 16 (3)-- March 1, 2004 ...[Visit Journal] We report continuous-wave (CW) operation of quantum-cascade lasers (λ=6 μm) up to a temperature of 313 K (40°C). The maximum CW optical output powers range from 212 mW at 288 K to 22 mW at 313 K and are achieved with threshold current densities of 2.21 and 3.11 kA/cm2, respectively, for a high-reflectivity-coated 12-μm-wide and 2-mm-long laser. At room temperature (298 K), the power output is 145 mW at 0.87 A, corresponding to a power conversion efficiency of 1.68%. The maximum CW operating temperature of double-channel ridge waveguide lasers mounted epilayer-up on copper heatsinks is analyzed in terms of the ridge width, which is varied between 12 and 40 μm. A clear trend of improved performance is observed as the ridge narrows. [reprint (PDF)]
14.	High operating temperature MWIR photon detectors based on Type II InAs/GaSb superlattice M. Razeghi, S. Abdollahi Pour, E.K. Huang, G. Chen, A. Haddadi and B.M. Nguyen SPIE Proceedings, Infrared Technology and Applications XXXVII, Orlando, FL, Vol. 8012, p. 80122Q-1-- April 26, 2011 ...[Visit Journal] Recent efforts have been paid to elevate the operating temperature of Type II superlattice Mid Infrared photon detectors. Using M-structure superlattice, novel device architectures have been developed, resulting in significant improvement of the device performances. In this paper, we will compare different photodetector architectures and discuss the optimization scheme which leads to almost one order of magnitude of improvement to the electrical performance. At 150K, single element detectors exhibit a quantum efficiency above 50%, and a specific detectivity of 1.05x10(12) cm.Hz(1/2)/W. BLIP operation with a 300K background and 2π FOV can be reached with an operating temperature up to 180K. High quality focal plane arrays were demonstrated with a noise equivalent temperature difference (NEDT) of 11mK up to 120K. Human body imaging is achieved at 150K with NEDT of 150mK. [reprint (PDF)]
14.	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)]
14.	Photoconductance measurements on InTlSb/InSb/GaAs grown by low-pressure metalorganic chemical vapor deposition P.T. Staveteig, Y.H. Choi, G. Labeyrie, E. Bigan, and M. Razeghi Applied Physics Letters 64 (4)-- January 24, 1994 ...[Visit Journal] We report infrared photoconductors based on InTlSb/InSb grown by low‐pressure metalorganic chemical vapor deposition on semi-insulating GaAs substrates. The photoresponse spectrum extends up to 8 μm at 77 K. The absolute magnitude of the photoresponse is measured as a function of bias. The specific detectivity is estimated to be 3×10⁸ Hz^½·cm·W^-1 at 7 μm wavelength. [reprint (PDF)]
14.	Pressure dependence study of the effective mass in Ga0.47In0.53As/InP heterojunctions D. Gauthier , L. Dmowski, J.C. Portal D. Leadley, M.A. Hopkins , M.A. Brummell , R.J. Nicholas, M. Razeghi, P. Maurel D. Gauthier, L. Dmowski, J.C. Portal, D. Leadley, M.A. Hopkins, M.A. Brummell, R.J. Nicholas, M. Razeghi, P. Maurel, Pressure dependence study of the effective mass in Ga0.47In0.53As/InP heterojunctions, Superlattices and Microstructures, Volume 4, Issue 2, 1988, Pages 201-206-- August 17, 1987 ...[Visit Journal] A study of the effective mass in GaInAs/InP heterojunctions under hydrostatic pressure up to 15 kbars is presented. Earlier results have shown the importance of hydrostatic pressure effects on the band parameters of the heterojunction to explain the experimental decrease of the carrier concentration with pressure at the interface (1). Here magnetophonon resonance experiments are performed to work out the increase of mass with pressure in our samples. The effective mass at atmospheric pressure is deduced from high temperature cyclotron resonance experiments and then used to calculate the frequency of the phonon interacting with the 2D electron gas (wo). The value of wo is found to be dependent on the carrier concentration of the measured samples. The lowest value is found for the highest carrier concentration sample. A band edge effective mass increase of 1 ± .1% kbar is found in the highest carrier concentration sample. This is two times smaller than the rate found experimentally in GaInAs bulk material and slightly smaller than in an AlInAs/GaInAs heterojunction. The experimental increase could be fitted with multiband k.p theory assuming no pressure dependence for the conduction band-valence band matrix element Ep. However at lower concentration a variation of the matrix element Ep with pressure has to be considered. [reprint (PDF)]
14.	Electron capture processes in optically excited In0.53Ga 0.47As/InP quantum wells U. Cebulla, G. Bacher, A. Forchel, D. Schmitz, H. Jürgensen, M. Razeghi Appl. Phys. Lett. 55, 933–935 (1989)-- September 4, 1989* ...[Visit Journal] We have performed picosecond time-resolved measurements on Ir:.O. 53 GaO. 47 As/lnP quantum wells with varying barrier thicknesses using 10 ps Nd:Y AG excitation. For this excitation, holes and electrons are created in the Ino . 53 GaOA7 As layers. Due to momentum conservation the Nd:YAG excitation accelerates the electrons above the InP barrier where they can diffuse but cannot recombine. By examining the rise time of the quantum well emission, we can show that for samples with thick barriers, the harrier geometry largely controls the dynamic properties of the carriers after Nd:YAG excitation. [reprint (PDF)]
14.	Room temperature quantum cascade lasers with 27% wall plug efficiency Y. Bai, N. Bandyopadhyay, S. Tsao, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 98, No. 18, p. 181102-1-- May 3, 2011 ...[Visit Journal] Using the recently proposed shallow-well design, we demonstrate InP based quantum cascade lasers (QCLs) emitting around 4.9 μm with 27% and 21% wall plug efficiencies in room temperature (298 K) pulsed and continuous wave (CW) operations, respectively. The laser core consists of 40 QCL-stages. The highest cw efficiency is obtained from a buried-ridge device with a ridge width of 8 μm and a cavity length of 5 mm. The front and back facets are antireflection and high-reflection coated, respectively. The maximum single facet cw power at room temperature amounts to 5.1 W. [reprint (PDF)]
14.	Very High Average Power at Room Temperature from λ ~ 5.9 μm Quantum Cascade Lasers J.S. Yu, S. Slivken, A. Evans, J. David and M. Razeghi Virtual Journal of Nanoscale Science & Technology 26-- May 26, 2003 ...[Visit Journal][reprint (PDF)]
14.	A review of the growth, doping, and applications of β-Ga₂O₃ thin films Manijeh Razeghi, Ji-Hyeon Park , Ryan McClintock, Dimitris Pavlidis, Ferechteh H. Teherani, David J. Rogers, Brenden A. Magill, Giti A. Khodaparast, Yaobin Xu, Jinsong Wu, Vinayak P. Dravid Proc. SPIE 10533, Oxide-based Materials and Devices IX, 105330R -- March 14, 2018 ...[Visit Journal] β-Ga₂O₃ is emerging as an interesting wide band gap semiconductor for solar blind photo detectors (SBPD) and high power field effect transistors (FET) because of its outstanding material properties including an extremely wide bandgap (Eg ~4.9eV) and a high breakdown field (8 MV/cm). This review summarizes recent trends and progress in the growth/doping of β-Ga₂O₃ thin films and then offers an overview of the state-of-the-art in SBPD and FET devices. The present challenges for β-Ga₂O₃ devices to penetrate the market in real-world applications are also considered, along with paths for future work. [reprint (PDF)]
14.	UV photodetectors based on Al_xGa_1-xN grown by MOCVD A. Saxler, D. Walker, X. Zhang, P. Kung, J. Xu, and M. Razeghi SPIE Photonics West '96 Photodetectors: Materials and Devices; Proceedings 2685-- January 27, 1996 ...[Visit Journal] Metalorganic chemical vapor deposition was used to deposit Al_xGa_1-xN active layers with varying aluminum compositions on basal plane sapphire substrate. Al_xGa_1-xN (x < 0.5) ultraviolet photodetectors have been fabricated and characterized with cut-off wavelengths as short as 260 nm. Carrier lifetimes on the order of 10 milliseconds were estimated from frequency dependent measurements of the responsivity. [reprint (PDF)]
14.	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)]
14.	III-Nitride Optoelectronic Devices: From ultraviolet detectors and visible emitters towards terahertz intersubband devices M. Razeghi, C. Bayram, Z. Vashaei, E. Cicek and R. McClintock IEEE Photonics Society 23rd Annual Meeting, November 7-10, 2010, Denver, CO, Proceedings, p. 351-352-- January 20, 2011 ...[Visit Journal] III-nitride optoelectronic devices are discussed. Ultraviolet detectors and visible emitters towards terahertz intersubband devices are reported. Demonstration of single photon detection efficiencies of 33% in the ultraviolet regime, intersubband energy level as low as in the mid-infrared regime, and GaN-based resonant tunneling diodes with negative resistance of 67 Ω are demonstrated. [reprint (PDF)]
14.	Widely Tunable, Single-Mode, High-Power Quantum Cascade Lasers M. Razeghi, B. Gokden, S. Tsao, A. Haddadi, N. Bandyopadhyay, and S. Slivken SPIE Proceedings, Intergreated Photonics: Materials, Devices and Applications, SPIE Microtechnologies Symposium, Prague, Czech Republic, April 18-20, 2011, Vol. 8069, p. 806905-1-- May 31, 2011 ...[Visit Journal] We demonstrate widely tunable high power distributed feedback quantum cascade laser array chips that span 190 nm and 200 nm from 4.4 um to 4.59 um and 4.5 um to 4.7 um respectively. The lasers emit single mode with a very narrow linewidth and side mode suppression ratio of 25 dB. Under pulsed operation power outputs up to 1.85 W was obtained from arrays with 3 mm cavity length and up to 0.95 W from arrays with 2 mm cavity length at room temperature. Continuous wave operation was also observed from both chips with 2 mm and 3 mm long cavity arrays up to 150 mW. The cleaved size of the array chip with 3 mm long cavities was around 4 mm x 5 mm and does not require sensitive external optical components to achieve wide tunability. With their small size and high portability, monolithically integrated DFB QCL Arrays are prominent candidates of widely tunable, compact, efficient and high power sources of mid-infrared radiation for gas sensing. [reprint (PDF)]
14.	High magnetic field studies of the two‐dimensional electron gas in GaInAs‐InP superlattices J. C. Portal; R. J. Nicholas; M. A. Brummell; M. Razeghi; M. A. Poisson J. C. Portal, R. J. Nicholas, M. A. Brummell, M. Razeghi, M. A. Poisson; High magnetic field studies of the two‐dimensional electron gas in GaInAs‐InP superlattices. Appl. Phys. Lett. 1 August 1983; 43 (3): 293–295.-- August 1, 1983 ...[Visit Journal] We report the observation of Shubnikov–de Haas oscillations in superlattices of GaInAs and InP, showing evidence of two‐dimensional behavior. The electron g‐factor is deduced from both the criteria for resolution of a spin splitting by comparison with the broadening parameter Γ, and from the tilted field method, and is shown to increase with increasing resolution of the Landau levels in a manner consistent with the theory of Ando and Uemura. In the ultraquantum limit, structure at ν=1/2 and ν=1/3 is observed. [reprint (PDF)]
14.	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)]
14.	Recent Advances in LWIR Type-II InAs/GaSb Superlattice Photodetectors and Focal Plane Arrays at the Center for Quantum Devices M. Razeghi, D. Hoffman, B.M. Nguyen, P.Y. Delaunay, E.K. Huang, M.Z. Tidrow, and V. Nathan IEEE Proceedings, Vol. 97, No. 6, p. 1056-1066-- June 1, 2009 ...[Visit Journal] In recent years, Type-II InAs/GaSb superlattice photo-detectors have experienced significant improvements in material quality, structural designs, and imaging applications. They now appear to be a possible alternative to the state-of-the-art HgCdTe (MCT) technology in the long and very long wavelength infrared regimes. At the Center for Quantum Devices, we have successfully realized very high quantum efficiency, very high dynamic differential resistance R₀A - product LWIR Type – II InAs/GaSb superlattice photodiodes with efficient surface passivation techniques. The demonstration of high quality LWIR Focal Plane Arrays that were 100 % fabricated in - house reaffirms the pioneer position of this university-based laboratory. [reprint (PDF)]
14.	Background limited long wavelength infrared type-II InAs/GaSb superlattice photodiodes operating at 110 K B.M. Nguyen, D. Hoffman, E.K. Huang, P.Y. Delaunay, and M. Razeghi Applied Physics Letters, Vol. 93, No. 12, p. 123502-1-- September 22, 2008 ...[Visit Journal] The utilization of the P+-pi-M-N+ photodiode architecture in conjunction with a thick active region can significantly improve long wavelength infrared Type-II InAs/GaSb superlattice photodiodes. By studying the effect of the depletion region placement on the quantum efficiency in a thick structure, we achieved a topside illuminated quantum efficiency of 50% for an N-on-P diode at 8.0 µm at 77 K. Both the double heterostructure design and the application of polyimide passivation greatly reduce the surface leakage, giving an R₀A of 416 Ω·cm² for a 1% cutoff wavelength of 10.52 µm, a Shot–Johnson detectivity of 8.1×10¹¹ cm·Hz^½/W at 77 K, and a background limited operating temperature of 110 K with 300 K background. [reprint (PDF)]
14.	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)]
14.	Minority electron unipolar photodetectors based on Type-II InAs/GaSb/AlSb superlattices for very long wavelength infrared detection B.M. Nguyen, S. Bogdanov, S. Abdollahi Pour, and M. Razeghi Applied Physics Letters, Vol. 95, No. 18, p. 183502-- November 2, 2009 ...[Visit Journal] We present a hybrid photodetector design that inherits the advantages of traditional photoconductive and photovoltaic devices. The structure consists of a barrier layer blocking the transport of majority holes in a p-type semiconductor, resulting in an electrical transport due to minority carriers with low current density. By using the M-structure superlattice as a barrier region, the band alignments can be experimentally controlled, allowing for the efficient extraction of the photosignal with less than 50 mV bias. At 77 K, a 14 µm cutoff detector exhibits a dark current 3.3 mA·cm⁻², a photoresponsivity of 1.4 A/W, and the associated shot noise detectivity of 4×10¹⁰ Jones. [reprint (PDF)]
14.	Study of Phase Transition in MOCVD Grown Ga2O3 from κ to β Phase by Ex Situ and In Situ Annealing Junhee Lee, Honghyuk Kim, Lakshay Gautam, Kun He, Xiaobing Hu, Vinayak P. Dravid and Manijeh Razeghi Photonics 2021, 8, 17. https://doi.org/10.3390/ photonics8010017 ...[Visit Journal] We report the post-growth thermal annealing and the subsequent phase transition of Ga2O3 grown on c-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). We demonstrated the post-growth thermal annealing at temperatures higher than 900 °C under N2 ambience, by either in situ or ex situ thermal annealing, can induce phase transition from nominally metastable κ- to thermodynamically stable β-phase. This was analyzed by structural characterizations such as high-resolution scanning transmission electron microscopy and x-ray diffraction. The highly resistive as-grown Ga2O3 epitaxial layer becomes conductive after annealing at 1000 °C. Furthermore, we demonstrate that in situ annealing can lead to a crack-free β-Ga2O3. [reprint (PDF)]
14.	Intermixing of GaInP/GaAs Multiple Quantum Wells C. Francis, M.A. Bradley, P. Boucaud, F.H. Julien and M. Razeghi Applied Physics Letters 62 (2)-- January 11, 1993 ...[Visit Journal] The intermixing of GaInP‐GaAs superlattices induced by a heat treatment is investigated as a function of the annealing temperature and duration. Photoluminescence experiments reveal a large red shift of the effective band gap of the annealed quantum wells thus indicating a dominant self‐diffusion of the group III atoms which is confirmed by secondary ion mass spectroscopic measurements. For long enough annealing durations, the red shift saturates and even decreases due to the competing slower self‐diffusion of the group V atoms. Experiments are well understood based on a simple diffusion model. [reprint (PDF)]
14.	High-power mid- and far- wavelength infrared lasers for free space communication M. Razeghi; A. Evans; J. Nguyen; Y. Bai; S. Slivken; S.R. Darvish; K. Mi Proc. SPIE 6593, Photonic Materials, Devices, and Applications II, 65931V (June 12, 2007)-- June 12, 2007 ...[Visit Journal] Laser-based free-space communications have been developed to serve specific roles in "last mile" high-speed data networks due to their high security, low cost, portability, and high bandwidth. Conventional free-space systems based on near infrared optical devices suffer from reliability problems due to atmospheric scattering losses and scintillation effects, such as those encountered with storms, dust, and fog. Mid-infrared wavelengths are less affected by atmospheric effects and can significantly enhance link up-time and range. This paper will discuss some of the recent advances in high-power, high temperature, high reliability mid-infrared Quantum Cascade Lasers and their potential application in highly reliable free space communication links. [reprint (PDF)]
14.	Use of PLD-grown moth-eye ZnO nanostructures as templates for MOVPE growth of InGaN-based photovoltaics Dave Rogers, V. E. Sandana, F. Hosseini Teherani, S. Gautier, G. Orsal, T. Moudakir, M. Molinari, M. Troyon, M. Peres, M. J. Soares, A. J. Neves, T. Monteiro, D. McGrouther, J. N. Chapman, H. J. Drouhin, M. Razeghi, and A. Ougazzaden Renewable Energy and the Environment, OSA Technical Digest paper PWB3, Optical Society of America, (2011)-- November 2, 2011 ...[Visit Journal] At this time, no abstract is available. Scopus has content delivery agreements in place with each publisher and currently contains 30 million records with an abstract. An abstract may not be present due to incomplete data, as supplied by the publisher, or is still in the process of being indexed. [reprint (PDF)]
14.	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)]

Page 19 of 30: Prev << 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 >> Next (738 Items)