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301.  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
 
302.  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
 
303.  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
 
304.  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 Gth and maximum CW operating temperature of the QCLs. reprint
 
305.  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
 
306.  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
 
307.  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
 
308.  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
 
309.  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
 
310.  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·Hz½/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
 
311.  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
 
312.  High-Power Distributed-Feedback Quantum Cascade Lasers
W.W. Bewley, I. Vurgaftman, C.S. Kim, J.R. Meyer, J. Nguyen, A.J. Evans, J.S. Yu, S.R. Darvish, S. Slivken and M. Razeghi
SPIE Conference, San Jose, CA, Vol. 6127, pp. 612704-- January 23, 2006
Recently, a distributed-feedback quantum cascade laser operating in a single spectral mode at 4.8 µm and at temperatures up to 333 K has been reported. In the present work, we provide detailed measurements and modeling of its performance characteristics. The sidemode suppression ratio exceeds 25 dB, and the emission remains robustly single-mode at all currents and temperatures tested. Cw output powers of 99 mW at 298 K and 357 mW at 200 K are obtained at currents well below the thermal rollover point. reprint
 
313.  High Power, Continuous-Wave, Quantum Cascade Lasers for MWIR and LWIR Applications
S. Slivken, A. Evans, J.S. Yu, S.R. Darvish and M. Razeghi
SPIE Conference, San Jose, CA, Vol. 6127, pp. 612703-- January 23, 2006
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. Since 2002, the power levels for individual devices have jumped from 20 mW to 600 mW. Expanding on this development, we have able to demonstrate continuous wave operation at many wavelengths throughout the mid- and far-infrared spectral range, and have now achieved >100 mW output in the 4.0 to 9.5 µm range. reprint
 
314.  Improved performance of quantum cascade lasers via manufacturable quality epitaxial side down mounting process utilizing aluminum nitride heatsinks
A. Tsekoun, R. Go, M. Pushkarsky, M. Razeghi, C.K.N. Patel
SPIE Conference, San Jose, CA, Vol. 6127, pp. 612702-- January 23, 2006
We report substantially improved performance of high power quantum cascade lasers by utilizing epi-side down mounting that provides superior heat dissipation properties. We have obtained CW power output of 450 mW at 20°C from mid-IR QCLs. The improved thermal management achieved with epi-side down mounting has also permitted us to carry out initial lifetime tests on the mid-IR QCLs. No degradation of power output is seen even after over 300 hours of CW operation at 25°C with power output in excess of 300 mW. We believe these improvements should permit incorporation of mid-IR QCLs in reliable instrumentation. reprint
 
315.  Fabrication of GaN Nanotubular Material using MOCVD with an Aluminium Oxide Membrane
W.G. Jung, S.H. Jung, P. Kung, and M. Razeghi
Nanotechnology 17-- January 1, 2006
GaN nanotubular material is fabricated with an aluminium oxide membrane in MOCVD. SEM, XRD, TEM and PL are employed to characterize the fabricated GaN nanotubular material. An aluminium oxide membrane with ordered nanoholes is used as a template. Gallium nitride is deposited at the inner wall of the nanoholes in the aluminium oxide template, and the nanotubular material with high aspect ratio is synthesized using the precursors of TMG and ammonia gas. Optimal synthesis conditions in MOCVD are obtained successfully for the gallium nitride nanotubular material in this research. The diameter of the GaN nanotube fabricated is approximately 200–250 nm and the wall thickness is about 40–50 nm. reprint
 
316.  Avalanche multiplication in AlGaN based solar-blind photodetectors
R. McClintock, A. Yasan, K. Minder, P. Kung, and M. Razeghi
Applied Physics Letters, 87 (24)-- December 12, 2005
Avalanche multiplication has been observed in solar-blind AlGaN-based p-i-n photodiodes. Upon ultraviolet illumination, the optical gain shows a soft breakdown starting at relatively low electric fields, eventually saturating without showing a Geiger mode breakdown. The devices achieve a maximum optical gain of 700 at a reverse bias of 60 V. By modeling the device, it is found that this corresponds to an electric-field strength of 1.7 MV/cm. reprint
 
317.  Negative and positive luminescence in mid-wavelength infrared InAs/GaSb superlattice photodiodes
D. Hoffman, A. Gin, Y. Wei, A. Hood, F. Fuchs, and M. Razeghi
IEEE Journal of Quantum Electronics, 41 (12)-- December 1, 2005
The quantum efficiency of negative and positive luminescence in binary type-II InAs-GaSb superlattice photodiodes has been investigated in the midinfrared spectral range around the 5-μm wavelength. The negative luminescence efficiency is nearly independent on temperature in the entire range from 220 to 325 K. For infrared diodes with a 2-μm absorbing layer, processed without anti-reflection coating, a negative luminescence efficiency of 45% is found, indicating very efficient minority carrier extraction. The temperature dependent measurements of the quantum efficiency of the positive luminescence enables for the determination of the capture cross section of the Shockley-Read-Hall centers involved in the competing nonradiative recombination. reprint
 
318.  Negative luminescence of long-wavelength InAs/GaSb superlattice photodiodes
D. Hoffman, A. Hood, Y. Wei, A. Gin, F. Fuchs, and M. Razeghi
Applied Physics Letters 87 (20)-- November 14, 2005
The electrically pumped emission behavior of binary type-II InAs/GaSb superlattice photodiodes has been studied in the spectral range between 8 µm and 13 µm. With a radiometric calibration of the experimental setup, the internal and external quantum efficiency has been determined in the temperature range between 80 K and 300 K for both, the negative and positive luminescence. The negative luminescence efficiency approaches values as high as 35% without antireflection coating. The temperature dependence of the internal quantum efficiency near zero-bias voltage allows for the determination of the electron-hole-electron Auger recombination coefficient of Γn=1×1024 cm6 s–1. reprint
 
319.  Characterization and Analysis of Single-Mode High-Power CW Quantum-Cascade Laser
W.W. Bewley, I. Vurgaftman, C.S. Kim, J.R. Meyer, J. Nguyen, A. Evans, J.S. Yu, S.R. Darvish, S. Slivken, and M. Razeghi
Journal of Applied Physics 98-- October 15, 2005
We measured and modeled the performance characteristics of a distributed-feedback quantum-cascade laser exhibiting high-power continuous-wave (CW) operation in a single spectral mode at λ~4.8 µm and temperatures up to 333 K. The sidemode suppression ratio exceeds 25 dB, and the emission remains robustly single mode at all currents and temperatures tested. CW output powers of 99 mW at 298 K and 357 mW at 200 K are obtained at currents well below the thermal rollover point. The slope efficiency and subthreshold amplified spontaneous emission spectra are shown to be consistent with a coupling coefficient of no more than κL ~ 4–5, which is substantially lower than the estimate of 9 based on the nominal grating fabrication parameters. reprint
 
320.  On the performance and surface passivation of type-II InAs/GaSb superlattice photodiodes for the very-long- wavelength infrared
A. Hood, M. Razeghi, E. Aifer, G.J. Brown
Applied Physics Letters 87 (1)-- October 10, 2005
We demonstrate very-long-wavelength infrared Type-II InAs/GaSb superlattice photodiodes with a cutoff wavelength (λc,50%) of 17 μm. We observed a zero-bias, peak Johnson noise-limited detectivity of 7.63×109 cm·Hz½/W at 77 K with a 90%-10% cutoff width of 17 meV, and quantum efficiency of 30%. Variable area diode zero-bias resistance-area product (R0A) measurements indicated that silicon dioxide passivation increased surface resistivity by nearly a factor of 5, over unpassivated photodiodes, and increased overall R0A uniformity. The bulk R0A at 77 K was found to be 0.08 Ω·cm2, with RA increasing more than twofold at 25 mV reverse bias. reprint
 
321.  Quantum Dot Infrared Photodetectors: Comparison Experiment and Theory
H. Lim, W. Zhang, S. Tsao, T. Sills, J. Szafraniec, K. Mi, B. Movaghar, and M. Razeghi
Virtual Journal of Nanoscale Science and Technology 12 (9)-- August 29, 2005reprint
 
322.  Quantum Dot Infrared Photodetectors: Comparison Experiment and Theory
H. Lim, W. Zhang, S. Tsao, T. Sills, J. Szafraniec, K. Mi, B. Movaghar, and M. Razeghi
Physical Review B, 72-- August 17, 2005
We present data and calculations and examine the factors that determine the detectivities in self-assembled InAs and InGaAs based quantum dot infrared photodetectors (QDIPs). We investigate a class of devices that combine good wavelength selectivity with “high detectivity.” We study the factors that limit the temperature performance of quantum dot detectors. For this we develop a formalism to evaluate the optical absorption and the electron transport properties. We examine the performance limiting factors and compare theory with experimental data. We find that the notion of a phonon bottleneck does not apply to large-diameter lenslike quantum dots, which have many closely spaced energy levels. The observed strong decrease of responsivity with temperature is ultimately due to a rapid thermal cascade back into the ground states. High temperature performance is improved by engineering the excited state to be near the continuum. The good low temperature (77 K) performance in strongly bound QDIPs is shown to be due to the high gain and the low noise achievable in these micron size devices. reprint
 
323.  High-power, room-temperature and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ = 4.8 µm
J.S. Yu, S. Slivken, S.R. Darvish, A. Evans, B. Gokden and M. Razeghi
Virtual Journal of Nanoscale Science and Technology 12 (5)-- August 1, 2005reprint
 
324.  High-power, room-temperature and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ = 4.8 µm
J.S. Yu, S. Slivken, S.R. Darvish, A. Evans, B. Gokden and M. Razeghi
Applied Physics Letters, 87 (4)-- July 25, 2005
The authors present high-power continuous-wave (cw) operation of distributed-feedback quantum-cascade lasers. Continuous-wave output powers of 56 mW at 25 °C and 15 mW at 40 °C are obtained. Single-mode emission near 7.8 µm with a side-mode suppression ratio of >=30 dB and a tuning range of 2.83 cm−1 was obtained between 15 and 40 °C. The device exhibits no beam steering with a full width at half maximum of 27.4° at 25 °C in cw mode. reprint
 
325.  Infrared detection from GaInAs/InP nanopillar arrays
A. Gin, B. Movaghar, M. Razeghi and G.J. Brown
Nanotechnology 16-- July 1, 2005
We report on the photoresponse from large arrays of 40 nm radius nanopillars with sensitivity in the long-wavelength infrared regime. Using photoluminescence techniques, a peak wavelength blue shift of approximately 5 meV was observed at 30 K from GaInAs/InP nanopillar structures, indicating carrier confinement effects. Responsivity measurements at 30 K indicated peak wavelength response at about 8 µm with responsivity of 420 mA/W at −2 V bias. We have also measured the noise and estimated the peak detectivity to be 3×108 cm·Hz½·W−1 at 1 V reverse bias and 30 K. A maximum internal quantum efficiency of 4.5% was derived from experiment. Both the photo and the dark transport have been successfully modeled as processes that involve direct and indirect field-assisted tunneling as well as thermionic emission. The best agreement with experiment was obtained when allowances were made for the non-uniformity of barrier widths and electric field heating of carriers above the lattice temperature. reprint
 

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