Page 11 of 11:  Prev << 1 2 3 4 5 6 7 8 9 10 11    (266 Items)

1.  320x256 infrared focal plane array based on type-II InAs/GaSb superlattice with a 12 μm cutoff wavelength
P.Y. Delaunay, B.M. Nguyen, D. Hoffman, and M. Razeghi
SPIE Porceedings, Vol. 6542, Orlando, FL 2007, p. 654204-- April 9, 2007 ...[Visit Journal]
In the past few years, significant progress has been made in the structure design, growth and processing of Type-II InAs/GaSb superlattice photodetectors. Type-II superlattice demonstrated its ability to perform imaging in the middle and long infra-red range, becoming a potential competitor for technologies such as QWIP and HgCdTe. Using an empirical tight-binding model, we developed a superlattice design that matches the lattice parameter of GaSb substrates and presents a cutoff wavelength of 12 μm. Electrical and optical measurements performed on single element detectors at 77 K showed an R0A averaging 13 Ω·cm² and a quantum efficiency as high as 54%. 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. A 320x256 array of 25x25μm² pixels, hybridized to an Indigo Read Out Integrated Circuit, performed thermal imaging up to 185 K with an operability close to 97%. The noise equivalent temperature difference at 81 K presented a peak at 270 mK, corresponding to a mean value of 340 mK. [reprint (PDF)]
 
1.  Lateral epitaxial overgrowth of GaN films on sapphire and silicon substrates
P. Kung, D. Walker, M. Hamilton, J. Diaz, and M. Razeghi
Applied Physics Letters 74 (4)-- January 25, 1999 ...[Visit Journal]
We report the lateral epitaxial overgrowth of GaN films on (00.1) Al2O3 and (111) Si substrates by metalorganic chemical vapor deposition. The lateral epitaxial overgrowth on Si substrates was possible after achieving quasi-monocrystalline GaN template films on (111) Si substrates. X-ray diffraction, photoluminescence, scanning electron microscopy, and atomic force microscopy were used to assess the quality of the lateral epitaxial overgrown films. Lateral growth rates more than five times as high as vertical growth rates were achieved for both lateral epitaxial overgrowths of GaN on sapphire and silicon substrates. [reprint (PDF)]
 
1.  Review of high power frequency comb sources based on InP From MIR to THZ at CQD
Manijeh Razeghi, Quanyong Lu, Donghai Wu, Steven Slivken
Event: SPIE Optical Engineering + Applications, 2018, San Diego, California, United States-- September 14, 2018 ...[Visit Journal]
We present the recent development of high performance compact frequency comb sources based on mid-infrared quantum cascade lasers. Significant performance improvements of our frequency combs with respect to the continuous wave power output, spectral bandwidth, and beatnote linewidth are achieved by systematic optimization of the device's active region, group velocity dispersion, and waveguide design. To date, we have demonstrated the most efficient, high power frequency comb operation from a free-running room temperature continuous wave (RT CW) dispersion engineered QCL at λ~5-9 μm. In terms of bandwidth, the comb covered a broad spectral range of 120 cm−1 with a radio-frequency intermode beatnote spectral linewidth of 40 Hz and a total power output of 880 mW at 8 μm and 1 W at ~5.0 μm. The developing characteristics show the potential for fast detection of various gas molecules. Furthermore, THz comb sources based on difference frequency generation in a mid-IR QCL combs could be potentially developed. [reprint (PDF)]
 
1.  Characterization of ZnO thin films grown on c-sapphire by pulsed laser deposition as templates for regrowth of zno by metal organic chemical vapor deposition
D. J. Rogers ; F. Hosseini Teherani ; C. Sartel ; V. Sallet ; F. Jomard ; P. Galtier ; M. Razeghi
Proc. SPIE 7217, Zinc Oxide Materials and Devices IV, 72170F (February 17, 2009)-- February 17, 2009 ...[Visit Journal]
The use of ZnO template layers grown Pulsed Laser Deposition (PLD) has been seen to produce dramatic improvements in the surface morphology, crystallographic quality and optical properties of ZnO layers grown on c-sapphire substrates by Metal Organic Chemical Vapor Deposition. This paper provides complementary details on the PLD-grown ZnO template properties. [reprint (PDF)]
 
1.  Type-II InAs/GaSb photodiodes and focal plane arrays aimed at high operating temperatures
M. Razeghi, S. Abdollahi Pour, E.K. Huang, G. Chen, A. Haddadi, and B.M. Nguyen
Opto-Electronics Review (OER), Vol. 19, No. 3, June 2011, p. 46-54-- June 1, 2011 ...[Visit Journal]
Recent efforts to improve the performance of type-II InAs/GaSb superlattice photodiodes and focal plane arrays (FPA) have been reviewed. The theoretical bandstructure models have been discussed first. A review of recent developments in growth and characterization techniques is given. The efforts to improve the performance of MWIR photodiodes and focal plane arrays (FPAs) have been reviewed and the latest results have been reported. It is shown that these improvements has resulted in background limited performance (BLIP) of single element photodiodes up to 180 K. FPA shows a constant noise equivalent temperature difference (NEDT) of 11 mK up to 120 K and it shows human body imaging up to 170 K. [reprint (PDF)]
 
1.  Low frequency noise in 1024 x 1024 long wavelength infrared focal plane array base on Type-II InAs/GaSb superlattice
A. Haddadi, S.R. Darvish, G. Chen, A.M. Hoang, B.M. Nguyen and M. Razeghi
SPIE Proceedings, Vol. 8268, p. 82680X-- January 22, 2012 ...[Visit Journal]
Recently, the type-II InAs/GaSb superlattice (T2SL) material platform is considered as a potential alternative for HgCdTe technology in long wavelength infrared (LWIR) imaging. This is due to the incredible growth in the understanding of its material properties and improvement of device processing which leads to design and fabrication of better devices. In this paper, we report electrical low frequency noise measurement on a high performance type-II InAs/GaSb superlattice 1024×1024 LWIR focal plane array. [reprint (PDF)]
 
1.  High power operation of λ ∼ 5.2–11 μm strain balanced quantum cascade lasers based on the same material composition
N. Bandyopadhyay, Y. Bai, S. Slivken, and M. Razeghi
Appl. Phys. Lett. 105, 071106 (2014)-- August 20, 2014 ...[Visit Journal]
A technique based on composite quantum wells for design and growth of strain balanced Al0.63In0.37As/Ga0.35In0.65As/Ga0.47In0.53As quantum cascade lasers (QCLs) by molecular beam epitaxy (MBE), emitting in 5.2–11 μm wavelength range, is reported. The strained Al0.63In0.37As provides good electron confinement at all wavelengths, and strain balancing can be achieved through composite wells of Ga0.35In0.65As/Ga0.47In0.53As for different wavelength. The use of these fixed composition materials can avoid the need for frequent calibration of a MBE reactor to grow active regions with different strain levels for different wavelengths. Experimental results for QCLs emitting at 5.2, 6.7, 8.2, 9.1, and 11 μm exhibit good wall plug efficiencies and power across the whole wavelength range. It is shown that the emission wavelength can be predictably changed using the same design template. These lasers are also compatible with a heterogeneous broadband active region, consisting of multiple QCL cores, which can be produced in a single growth run. [reprint (PDF)]
 
1.  Low-Threshold 7.3 μm Quantum Cascade Lasers Grown by Gas-Source Molecular Beam Epitaxy
S. Slivken, A. Matlis, A. Rybaltowski, Z. Wu and M. Razeghi
Applied Physics Letters 74 (19)-- May 19, 1999 ...[Visit Journal]
We report low-threshold 7.3 μm superlattice-based quantum cascade lasers. The threshold current density is 3.4 kA/cm² at 300 K and 1.25 kA/cm² at 79 K in pulsed mode for narrow (∼20 μm), 2 mm-long laser diodes. The characteristic temperature (T0) is 210 K. The slope efficiencies are 153 and 650 mW/A at 300 and 100 K, respectively. Power output is in excess of 100 mW at 300 K. Laser far-field intensity measurements give divergence angles of 64° and 29° in the growth direction and in the plane of the quantum wells, respectively. Far-field simulations show excellent agreement with the measured results. [reprint (PDF)]
 
1.  Growth of AlxGa1-xN:Ge on sapphire and silicon substrates
X. Zhang, P. Kung, A. Saxler, D. Walker, T.C. Wang, and M. Razeghi
Applied Physics Letters 67 (12)-- September 18, 1995 ...[Visit Journal]
AlxGa1–xN were grown on (00.1) sapphire and (111) silicon substrates in the whole composition range (0 <= x <= 1). The high optical quality of the epilayers was assessed by room-temperature optical absorption and photoluminescence measurements. Layers with higher Al composition are more resistive. Resistive AlxGa1–xN epilayers were successfully doped with Ge and free-electron concentration as high as 3 × 1019 cm–3 was achieved. [reprint (PDF)]
 
1.  III-Nitride Optoelectronic Devices: From Ultraviolet Toward Terahertz
M. Razeghi
IEEE Photonics Journal-Breakthroughs in Photonics 2010, Vol. 3, No. 2, p. 263-267-- April 26, 2011 ...[Visit Journal]
We review III-Nitride optoelectronic device technologies with an emphasis on recent breakthroughs. We start with a brief summary of historical accomplishments and then report the state-of-the-art in three key spectral regimes: (1) Ultraviolet (AlGaN-based avalanche photodiodes, single photon detectors, focal plane arrays, and light emitting diodes), (2) Visible (InGaN-based solid state lighting, lasers, and solar cells), and (3) Near-, mid-infrared, and terahertz (AlGaN/GaN-based gap-engineered intersubband devices). We also describe future trends in III-Nitride optoelectronic devices. [reprint (PDF)]
 
1.  Progress in monolithic, broadband, widely tunable midinfrared quantum cascade lasers
Manijeh Razeghi Wenjia Zhou Ryan McClintock Donghai Wu Steven Slivken
Optical Engineering 57(1), 011018-- December 1, 2017 ...[Visit Journal]
We present recent progress on the development of monolithic, broadband, widely tunable midinfrared quantum cascade lasers. First, we show a broadband midinfrared laser gain realized by a heterogeneous quantum cascade laser based on a strain balanced composite well design of Al0.63In0.37As∕Ga0.35In0.65As∕ Ga0.47In0.53As. Single mode emission between 5.9 and 10.9 μm under pulsed mode operation was realized from a distributed feedback laser array, which exhibited a flat current threshold across the spectral range. Using the broadband wafer, a monolithic tuning between 6.2 and 9.1 μm was demonstrated from a beam combined sampled grating distributed feedback laser array. The tunable laser was utilized for a fast sensing of methane under pulsed operation. Transmission spectra were obtained without any moving parts, which showed excellent agreement to a standard measurement made by a Fourier transform infrared spectrometer. [reprint (PDF)]
 
1.  Uncooled operation of Type-II InAs/GaSb superlattice photodiodes in the mid- wavelength infrared range
Y. Wei, A. Hood, H. Yau, A. Gin, M. Razeghi, M.Z. Tidrow, V. Natha
Applied Physics Letters, 86 (23)-- June 6, 2005 ...[Visit Journal]
We report high performance uncooled midwavelength infrared photodiodes based on interface-engineered InAs/GaSb superlattice. Two distinct superlattices were designed with a cutoff wavelength around 5 µm for room temperature and 77 K. The device quantum efficiency reached more than 25% with responsivity around 1 A/W. Detectivity was measured around 109 cm·Hz½/W at room temperature and 1.5×1013 cm·Hz½/W at 77 K under zero bias. The devices were without antireflective coating. The device quantum efficiency stays at nearly the same level within this temperature range. Additionally, Wannier–Stark oscillations in the Zener tunneling current were observed up to room temperature. [reprint (PDF)]
 
1.  High performance long wavelength infrared mega-pixel focal plane array based on type-II superlattices
P. Manurkar, S.R. Darvish, B.M. Nguyen, M. Razeghi and J. Hubbs
Applied Physics Letters, Vol. 97, No 19, p. 193505-1-- November 8, 2010 ...[Visit Journal]
A large format 1k × 1k focal plane array (FPA) is realized using type-II superlattice photodiodes for long wavelength infrared detection. Material growth on a 3 in. GaSb substrate exhibits a 50% cutoff wavelength of 11 μm across the entire wafer. The FPA shows excellent imaging. Noise equivalent temperature differences of 23.6 mK at 81 K and 22.5 mK at 68 K are achieved with an integration time of 0.13 ms, a 300 K background and f/4 optics. We report a dark current density of 3.3×10−4 A·cm−2 and differential resistance-area product at zero bias R0A of 166 Ω·cm² at 81 K, and 5.1×10−5 A·cm−2 and 1286 Ω·cm², respectively, at 68 K. The quantum efficiency obtained is 78%. [reprint (PDF)]
 
1.  Mid-infrared quantum cascade lasers with high wall plug efficiency
Y. Bai, B. Gokden, S. Slivken, S.R. Darvish, S.A. Pour, and M. Razeghi
SPIE Proceedings, San Jose, CA Volume 7222-0O-- January 26, 2009 ...[Visit Journal]
We demonstrate optimization of continuous wave (cw) operation of 4.6 µm quantum cascade lasers (QCLs). A 19.7 µm by 5 mm, double channel processed device exhibits 33% cw WPE at 80 K. Room temperature cw WPE as high as 12.5% is obtained from a 10.6 µm by 4.8 mm device, epilayer-down bonded on a diamond submount. With the semi-insulating regrowth in a buried ridge geometry, 15% WPE is obtained with 2.8 W total output power in cw mode at room temperature. This accomplishment is achieved by systematically decreasing the parasitic voltage drop, reducing the waveguide loss and improving the thermal management. [reprint (PDF)]
 
1.  RT-CW: widely tunable semiconductor THz QCL sources
M. Razeghi; Q. Y. Lu
Proceedings Volume 9934, Terahertz Emitters, Receivers, and Applications, 993406-1-- September 26, 2017 ...[Visit Journal]
Distinctive position of Terahertz (THz) frequencies (ν~0.3 -10 THz) in the electromagnetic spectrum with their lower quantum energy compared to IR and higher frequency compared to microwave range allows for many potential applications unique to them. Especially in the security side of the THz sensing applications, the distinct absorption spectra of explosives and related compounds in the range of 0.1–5 THz makes THz technology a competitive technique for detecting hidden explosives. A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range will greatly boost the THz applications for the diagnosis and detection of explosives. Here we present a new strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based intracavity DFG. Room temperature continuous wave operation with electrical frequency tuning range of 2.06-4.35 THz is demonstrated [reprint (PDF)]
 
1.  High-Performance Type-II InAs/GaSb Superlattice Photodiodes with Cutoff Wavelength Around 7 µm
Y. Wei, A. Hood, H. Yau, V. Yazdanpanah, M. Razeghi, M.Z. Tidrow and V. Nathan
Applied Physics Letters, 86 (9)-- February 28, 2005 ...[Visit Journal]
We report the most recent result in the area of type-II InAs/GaSb superlattice photodiodes that have a cutoff wavelength around 7 µm at 77 K. Superlattice with a period of 40 Å lattice matched to GaSb was realized using GaxIn1–x type interface engineering technique. Compared with significantly longer period superlattices, we have reduced the dark current density under reverse bias dramatically. For a 3 µm thick structure, using sulfide-based passivation, the dark current density reached 2.6×10–5 A/cm2 at –3 V reverse bias at 77 K. At this temperature the photodiodes have R0A of 9300 Ω·cm2 and a thermally limited zero bias detectivity of 1×1012 cm·Hz½/W. The 90%–10% cutoff energy width was only 16.5 meV. The devices did not show significant dark current change at 77 K after three months storage in the atmosphere. [reprint (PDF)]
 

Page 11 of 11:  Prev << 1 2 3 4 5 6 7 8 9 10 11    (266 Items)