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426.  Quantum Dots of InAs/GaSb Type-II Superlattice for Infrared Sensing
M. Razeghi, Y. Wei, A. Gin and G.J. Brown
Materials Research Society Fall Meeting, Boston, MA; MRS Symposium Proceedings, Vol. 692 (H3.1)-- November 26, 2001
Throughout the past years, significant progress has been made in Type-II (InAs/GaSb) photovoltaic detectors in both LWIR and VLWIR ranges. BLIP performance at 60K for 16 μm photovoltaic Type-II detectors has been successfully demonstrated for the first time. The detectors had a 50% cut-off wavelength of 18.8 μm and a peak current responsivity of 4 A/W at 80K. A peak detectivity of 4.5×1010cm·Hz1/2/W was achieved at 80K at a reverse bias of 110mV. Detectors of cutoff wavelength up to 25μm have been demonstrated at 77K. The great performance of single element detectors appeals us to lower dimensional structures for both higher temperature performance and possible wavelength tunability. Simple calculations show that quantum effects will become significant when the lateral confinement is within tens of nanometers. The variation of applied gate voltage will move the electron and hole energy levels unevenly. The cutoff wavelength of the superlattice will vary accordingly. Auger recombination will also decrease and higher temperature operation becomes possible. In this talk, the latest results will be discussed.
 
427.  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
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
 
428.  Long Wavelength Type-II Photodiodes Operating at Room Temperature
H. Mohseni and M. Razeghi
IEEE Photonics Technology Letters 13 (5)-- May 1, 2001
The operation of uncooled InAs-GaSb superlattice photodiodes with a cutoff wavelength of λc=8 μm and a peak detectivity of 1.2 × 108 cm·Hz½/W at zero bias is demonstrated. The detectivity is similar to the best uncooled HgCdTe detectors and microbolometers. However, the R0A product is more than two orders of magnitude higher than HgCdTe and the device is more than four orders of magnitude faster than microbolometers. These features combined with their low 1/f noise and high uniformity make these type-II photodiodes an excellent choice for uncooled high-speed IR imaging arrays reprint
 
429.  High Performance InAs/GaSb Superlattice Photodiodes for the Very Long Wavelength Infrared Range
H. Mohseni, M. Razeghi, G.J. Brown, Y.S. Park
Applied Physics Letters 78 (15)-- April 9, 2001
We report on the demonstration of high-performance p-i-n photodiodes based on type-II InAs/GaSb superlattices with 50% cut-off wavelength λc = 16 μm operating at 80 K. Material is grown by molecular beam epitaxy on GaSb substrates with excellent crystal quality as evidenced by x-ray diffraction and atomic force microscopy. The processed devices show a current responsivity of 3.5 A/W at 80 K leading to a detectivity of ∼ 1.51×1010 cm·Hz½/W. The quantum efficiency of these devices is about 35% which is comparable to HgCdTe detectors with a similar active layer thickness. reprint
 
430.  Miniaturization: enabling technology for the new millennium
M. Razeghi and H. Mohseni
SPIE International Conference on Solid State Crystals, Zakopane, Poland, -- April 1, 2001
The history of semiconductor devices has been characterized by a constant drive toward lower dimensions in order to increase integration density, system functionality and performance. However, this is still far from being comparable with the performance of natural systems such as human brain. The challenges facing semiconductor technologies in the millennium will be to move toward miniaturization. The influence of this trend on the quantum sensing of infrared radiation is one example that is elaborated here. A new generation of infrared detectors has been developed by growing layers of different semiconductors with nanometer thicknesses. The resulted badgap engineered semiconductor has superior performance compared to the bulk material. To enhance this technology further, we plan to move from quantum wells to quantum wire and quantum dots. reprint
 
431.  High performance quantum cascade lasers (~11 μm) operating at high temperature (T>= 425K)
A. Tahraoui, A. Matlis, S. Slivken, J. Diaz, and M. Razeghi
Applied Physics Letters 78 (4)-- January 22, 2001
We report record-low threshold current density and high output power for λ ∼ 11 μm Al0.48In0.52As/Ga0.47In0.53As quantum cascade lasers operating up to 425 K. The threshold current density is 1.1, 3.83, and 7.08 kA/cm² at 80, 300, and 425 K, respectively, for 5 μs pulses at a 200 Hz repetition rate. The cavity length is 3 mm with a stripe width of 20 μm. The maximum peak output power per facet is 1 W at 80 K, 0.5 W at 300 K, and more than 75 mW at 425 K. The characteristic temperature of these lasers is 174 K between 80 and 300 K and 218 K in the range of 300–425 K. reprint
 
432.  High Performance Quantum Cascade Lasers Grown by Gas-Source Molecular Beam Epitaxy
M. Razeghi, S. Slivken, A. Tahraoui and A. Matlis
SPIE Conference, San Jose, CA, -- January 22, 2001
Recent improvements in quantum cascade laser technology have led to a number of very impressive results. This paper is a brief summary of the technological development and state-of- the-art performance of quantum cascade lasers produced at the Center for Quantum Devices. Laser design will be discussed, as well as experimental details of device fabrication. Room temperature QCL operation has been reported for lasers emitting between 5 - 11 μm, with 9 - 11 μm lasers operating up to 425 K. We also demonstrate record room temperature peak output powers at 9 and 11 μm(2.5 W and 1 W respectively) as well as record low 80 K threshold current densities (250 A/cm²) for some laser designs. Finally, some of the current limitations to laser efficiency are mentioned, as well as a means to combat them. reprint
 
433.  Quantum Dot Intersubband Photodetectors
C. Jelen, M. Erdtmann, S. Kim, and M. Razeghi
SPIE Conference, San Jose, CA, -- January 22, 2001
Quantum dots are recognized as very promising candidates for the fabrication of intersubband photodetectors in the infrared spectral range. At present, material quality is making rapid progress and some devices have been demonstrated. Examples of mid-infrared quantum dot intersubband photodetectors are presented along with device design and data analysis. Nonetheless, the performance of these devices remains less than comparable quantum well intersubband photodetectors due to difficulties in controlling the quantum dot size and distribution during epitaxy. reprint
 
434.  Monolithic Integration of GaInAs/InP Quantum Well Infrared Photodetectors on Si Substrate
M. Erdtmann and M. Razeghi
SPIE Conference, San Jose, CA, -- January 22, 2001
Using low-pressure metalorganic chemical vapor deposition, we have grown GaInAs/InP QWIP structures on GaAs-coated Si substrate. First, the procedure to optimize the epitaxy of the InP buffer layer on Si substrate is given. Excellent crystallinity and a mirror-like surface morphology were obtained by using both a two-step growth process at the beginning of the InP buffer layer growth and several series of thermal cycle annealing throughout the InP buffer layer growth. Second, results of fabricated GaInAs/InP QWIPs on Si substrate are presented. At a temperature of 80 K, the peak response wavelength occurs at 7.4 μm. The responsivities of QWIPs on both Si and InP substrates with identical structures are equal up to biases of 1.5 V. At a bias of 3 V, the responsivity of the QWIPs on Si substrate is 1.0 A/W. reprint
 
435.  High Performance Type-II InAs/GaSb Superlattice Photodiodes
H. Mohseni, Y. Wei, and M. Razeghi
SPIE Conference, San Jose, CA, -- January 22, 2001
We report on the demonstration of high performance p-i-n photodiodes based on Type-II InAs/GaSb superlattices operating in the very long wavelength infrared (VLWIR) range at 80 K. Material is grown by molecular beam epitaxy on GaSb substrates with excellent crystal quality as evidenced by x-ray diffraction and atomic force microscopy. The processed devices with a 50% cutoff wavelength of λc equals 22 μm show a peak current responsivity about 5.5 A/W at 80 K. The use of binary layers in the superlattice has significantly enhanced the uniformity and reproducibility of the energy gap. The 90% to 10% cut-off energy width of these devices is on the order of 2 kT which is about four times smaller compared to the devices based on InAs/Ga1-xInxSb superlattices. Similar photovoltaic devices with cut-off wavelengths up to 25 μm have been measured at 80 K. Our experimental results shows excellent uniformity over a three inch wafer area, indicating the possibility of VLWIR focal plane arrays based on Type-II superlattices. reprint
 
436.  AlxGa1-xN Materials and Device Technology for Solar Blind Ultraviolet Photodetector Applications
R. McClintock, P. Sandvik, K. Mi, F. Shahedipour, A. Yasan, C. Jelen, P. Kung, and M. Razeghi
SPIE Conference, San Jose, CA, Vol. 4288, pp. 219-- January 22, 2001
There has been a growing interest for the development of solar blind ultraviolet (UV) photodetectors for use in a variety of applications, including early missile threat warning, flame monitoring, UV radiation monitoring and chemical/biological reagent detection. The AlxGa1-xN material system has emerged as the most promising approach for such devices. However, the control of the material quality and the device technology are still rather immature. We report here the metalorganic chemical vapor deposition, the n-type and the p-type doping of high quality AlxGa1-xN thin films on sapphire substrates over a wide range of Al concentration. reprint
 
437.  Novel Sb-based Alloys for Uncooled Infrared Photodetector Applications
M. Razeghi
SPIE Conference, San Jose, CA, -- January 22, 2001
We report on the growth and characterization of InSbBi, InTlSb, InTlP, and the quaternary alloys for uncooled long- wavelength infrared photodetector applications. The layers were grown on InSb and GaAs substrates by low-pressure metalorganic chemical vapor deposition. The incorporation of Bi and Tl in InSb was investigated with high-resolution x-ray diffraction, energy dispersive x-ray analysis, and optical photoresponse measurements. We also demonstrate the photodetectors fabricated from the grown InSbBi and InTlSb alloys. InSb0.96Bi0.04 photoconductive detectors exhibited a responsivity of 3.2 V/W at 77 K. The estimated Johnson noise limited detectivity at 7 micrometers was 1.7 X 108 cm·Hz½/W at 77 K. A room temperature operating InSb0.95Bi0.05 photodetector was also demonstrated. Photoresponse up to 12 micrometers was achieved at 300 K. The responsivity and Johnson noise-limited detectivity at 10.6 μm were 1.9 mV/W and 1.2 X 106 cm·Hz½/W, respectively. Photoresponse up to 15 μm was achieved at 300 K from quaternary InTlAsSb and InBiAsSb alloys. reprint
 
438.  Long-Wavelength Quantum Well Infrared Photodetectors
M. Razeghi, M. Erdtmann, C. Jelen, J. Diaz, F. Guastavino and Y.S. Park
-- January 1, 2001
 
439.  Miniaturization: enabling technology for the new millennium
M. Razeghi and H. Mohseni
-- January 1, 2001
 
440.  Development of Quantum Well Infrared Photodetectors at the Center for Quantum Devices
M. Razeghi, M. Erdtmann, C. Jelen, J. Diaz, F. Guastavino, G.J. Brown, and Y.S. Park
-- January 1, 2001
 
441.  AlxGa1-xN for Solar-Blind UV Detectors
P. Sandvik, K. Mi, F. Shahedipour, R. McClintock, A. Yasan, P. Kung, and M. Razeghi
Journal of Crystal Growth 231 (2001)-- January 1, 2001
We report on the metalorganic chemical vapor deposition of high quality AlGaN thin films on sapphire substrates over a wide range of Al concentrations. The quality of these AlGaN materials was verified through a demonstration of high performance visible and solar-blind UV p–i–n photodiodes with peak cutoff wavelengths ranging from 227 to 364 nm. External quantum efficiencies for these devices reached as high as 69% with over five orders rejection ratio from the peak to visible wavelengths. reprint
 
442.  Novel Sb-based Materials for Uncooled Infrared Photodetector Applications
J.J. Lee and M. Razeghi
-- December 1, 2000
 
443.  High Power Electrically Injected Mid-Infrared Interband Lasers Grown by LP-MOCVD
B. Lane and M. Razeghi
-- December 1, 2000
 
444.  Optoelectronic Devices Based on III-V Compound Semiconductors Which Have Made a Major Scientific and Technological Impact in the Past 20 Years
M. Razeghi
IEEE Journal of Selected Topics in Quantum Electronics 6 (6), pp.1344 - 1354 -- November 1, 2000
This paper reviews some of our pioneering contributions to the field of III–V compound semiconductor materials and low-dimensional optoelectronic devices. These contributions span from the ultraviolet (200 nm) up to the far-infrared (25 μm) portion of the electromagnetic spectrum and have had a major scientific and technological impact on the semiconductor world in the past 20 years. reprint
 
445.  Low-threshold and high power (~9.0 μm) quantum cascade lasers operating at room temperature
A. Matlis, S. Slivken, A. Tahraoui, K.J. Luo, J. Diaz, Z. Wu, A. Rybaltowski, C. Jelen, and M. Razeghi
Applied Physics Letters 77 (12)-- September 18, 2000
We report a low threshold current density and high power for λ ∼ 9 μm AlInAs/GaInAs quantum cascade lasers operating at room temperature. The threshold current density is 1.95 kA/cm² at 300 K and 0.61 kA/cm² at 80 K for 5 μs pulses at 200 Hz repetition rate. The peak output power is 700 mW at room temperature and 1.3 W at 80 K per two facets for cavity length is 3 mm with a stripe width of 20 μm. The characteristic temperature T0 is 185 °C. The slope efficiency is 450 and 800 mW/A at 300 and 80 K, respectively. In continuous wave operation, the output power is more than 150 mW at 80 K and 25 mW at 140 K. This high performance was achieved by improving the material growth and processing technology. reprint
 
446.  Very Long Wavelength Infrared Type-II Detectors Operating at 80K
H. Mohseni, A. Tahraoui, J. Wojkowski, M. Razeghi, G.J. Brown, W.C. Mitchel, and Y.S. Park
Applied Physics Letters 77 (11)-- September 11, 2000
We report a demonstration of very long wavelength infrared detectors based on InAs/GaSb superlattices operating at T = 80 K. Detector structures with excellent material quality were grown on an optimized GaSb buffer layer on GaAs semi-insulating substrates. Photoconductive devices with 50% cutoff wavelength of λc = 17  μm showed a peak responsivity of about 100 mA/W at T = 80  K. Devices with 50% cutoff wavelengths up to λc = 22  μm were demonstrated at this temperature. Good uniformity was obtained over large areas even for the devices with very long cutoff wavelengths. reprint
 
447.  III-Nitride Wide Bandgap Semiconductors: A Survey of the Current Status and Future Trends of the Material and Device technology
P. Kung and M. Razeghi
Opto-Electronics Review 8 (3)-- September 1, 2000
During the past decade, group III - Nitride wide bandgap semiconductors have become the focus of extremely intensive reearch because of their exceptional physical properties and their high potential for use in countless numbers of applications. Nearly all aspects have been investigated, from the fundamental physical understanding of these materials to the development of the fabrication technology and demonstration of commercial devices. The purpose of this paper is to review the physical properties of III-Nitrides, their areas of application, the current status of the material technology (AlN, AlGaN, GaN, GaInN) including synthesis and processing. The state-of-the-art of III-Nitride material quality, as well as the devices which have been demonstrated, including electronic devices, AlGaN ultraviolet photoconductors, ultraviolet photodiodes, visible light emitting diodes (LEDs) and ultraviolet - blue laser diodes, will also be presented.
 
448.  Quantum Well Infrared Photodetectors (3 - 20 μm) Focal Plane Arrays: Monolithic Integration with Si-based Readout-integrated Circuitry for Low Cost and High Performance
M. Razeghi, M. Erdtmann, C. Jelen, J. Diaz, F. Guastavino, G. J. Brown, and Y.S. Park
-- July 30, 2000
 
449.  Lateral Epitaxial Overgrowth of GaN on Sapphire and Silicon Substrates for Ultraviolet Photodetector Applications
M. Razeghi, P. Sandvik, P. Kung, D. Walker, K. Mi, X. Zhang, V. Kumar, J. Diaz, and F. Shahedipour
-- May 1, 2000
 
450.  High Power InAsSb/InAsSbP Electrical Injection Laser Diodes Emitting Between 3—5 μm
B. Lane, S. Tong, J. Diaz, Z. Wu, and M. Razeghi
-- May 1, 2000
 

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