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1.  Growth and characterization of InSbBi for long wavelength infrared photodetectors
J.J. Lee, J.D. Kim, and M. Razeghi
Applied Physics Letters 70 (24)-- June 16, 1997 ...[Visit Journal]
The epitaxial growth of InSbBi ternary alloys by low-pressure metalorganic chemical vapor deposition is reported on. X-ray diffraction spectra showed well resolved peaks of InSbBi and InSb films. Bi incorporation was confirmed by energy dispersive x-ray analysis. Photoresponse spectrum up to 9.3 μm which corresponds to 0.13 eV energy band gap has been measured in a sample with Bi composition of 5.8 at.% at 77 K. Electron mobility at room temperature ranges from 44 100 to 4910 cm²/V·s as Bi composition increases. [reprint (PDF)]
 
1.  Effect of the spin split-off band on optical absorption in p-type Ga1 xInxAsyP1-y quantum-well infrared detectors
J.R. Hoff, M. Razeghi and G. Brown
Physical Review B 54 (15)-- October 15, 1996 ...[Visit Journal]
Experimental investigations of p-type Ga1-xInxAsyP1-y quantum-well intersubband photodetectors (QWIP’s) led to the discovery of unique features in photoresponse spectra of these devices. In particular, the strong 2–5 μm photoresponse of these QWIP’s was not anticipated based on previous experimental and theoretical results for p-type GaAs/AlxGa1-xAs QWIP’s. Our theoretical modeling of p-type QWIP’s based on the Ga1-xInxAsyP1-y system revealed that the intense short-wavelength photoresponse was due to a much stronger coupling to the spin-orbit split-off components in the continuum than occurs for GaAs/AlxGa1-xAs QWIP’s. Due to the strong influence of the spin split-off band, an eight-band Kane Hamiltonian was required to accurately model the measured photoresponse spectra. This theoretical model is first applied to a standard p-type GaAs/Al0.3Ga0.7As QWIP, and then to a series of GaAs/Ga0.51In0.49P, GaAs/Ga0.62In0.38As0.22P0.78, Ga0.79In0.21As0.59P0.41/Ga0.51In0.49P, and Ga0.79In0.21As0.59P0.41/Ga0.62In0.38As0.22P0.78 QWIP’s. Through this analysis, the insignificance of spin split-off absorption in GaAs/AlxGa1-xAs QWIP’s is verified, as is the dual role of light-hole extended-state and spin split-off hole-extended-state absorption on the spectral shape of Ga1-xInxAsyP1-y QWIP’s. [reprint (PDF)]
 
1.  InTlSb alloys for infrared detection
E. Bigan, Y.H. Choi, G. Labeyrie, and M. Razeghi
Proceedings, SPIE Nonlinear Optics for High-Speed Electronics and Optical Frequency Conversion, Vol. 2145-- January 24, 1994 ...[Visit Journal]
InTISb alloys have been grown by low-pressure metalorganic chemical vapor deposition, and characterized. Photoconductors exhibit a cutoff wavelength that can be tailored from 5.5 μm up to 9 μm by varying the thallium content. Experimental observations suggest that this can be further extended by increasing the thallium content. An InTISb photoconductor having a 9 μm cutoff wavelength exhibited a D* of 109 cm·Hz½·W-1 at 7 μm operating wavelength. [reprint (PDF)]
 
1.  Temperature dependence of threshold current density Jth and differential efficiency of High Power InGaAsP/GaAs ( λ = 0.8 μm) lasers
H. Yi, J. Diaz, I. Eliashevich, M. Stanton, M. Erdtmann, X. He, L. Wang, and M. Razeghi
Applied Physics Letters 66 (3)-- January 16, 1995 ...[Visit Journal]
An experimental and theoretical study on temperature dependence of the threshold current density Jth and differential efficiency ηd for the InGaAsP/GaAs laser diodes emitting at λ=0.8 μm was performed. Threshold current density Jth increases and differential efficiency ηd decreases as temperature is increased mainly because of thermal broadening of the gain spectrum. However, the measured temperature dependence of Jth and ηd could not be explained when only this effect was considered. In this letter, the temperature dependence of momentum relaxation rate ℏ/τ of carriers was investigated by performing the photoluminescence study. At high temperature, increase of the momentum relaxation rate ℏ/τ leads to reduction of the gain and mobility and increase of the optical loss, causing higher Jth and lower ηd as experimentally observed. The resulting theoretical model provides a good explanation for the mechanism of the increase of Jth and decrease of ηd. [reprint (PDF)]
 
1.  Quntum Cascade Laser Breakthrough for Advanced Remote Detection
Manijeh Razeghi, Wenjia Zhou, Donghai Wu, Ryan McClintock, and Steven Slivken, Northwestern University
www.photonics.com-- November 1, 2016
The atoms in a molecule can bend, stretch and rotate with respect to one an­other, and these excitations are largely optically active. Most molecules, from simple to moderately complex, have a characteristic absorption spectrum in the 3- to 14-µrn wavelength range that can be uniquely identified and quantified in real time. Infrared spectroscopy has been used to study these absorption features and de­velop different molecular "fingerprints."
 
1.  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)]
 
1.  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)]
 
1.  Spatial Noise and Correctability of Type-II InAs/GaSb Focal Plane Arrays
P.Y. Delaunay and M. Razeghi
IEEE Journal of Quanutm Electronics, April 2010, Vol. 46, No. 4, p. 584-588-- April 1, 2010 ...[Visit Journal]
A long wavelength infrared focal plane array based on Type-II InAs/GaSb superlattices was fabricated and characterized at 80 K. The noise equivalent temperature difference of the array was measured as low as 23 mK (f# = 2), for an integration time of 0.129 ms. The spatial noise of the array was dominated by the nonuniformity of the illumination through the circular aperture. A standard two-point nonuniformity correction improved the inhomogeneity equivalent temperature difference to 16 mK. The correctability just after calibration was 0.6. The long-term stability time was superior to 25 hours. [reprint (PDF)]
 
1.  A hybrid green light-emitting diode comprised of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN
C. Bayram, F. Hosseini Teherani, D.J. Rogers and M. Razeghi
Applied Physics Letters, Vol. 93, No. 8, p. 081111-1-- August 25, 2008 ...[Visit Journal]
Hybrid green light-emitting diodes (LEDs) comprised of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN were grown on semi-insulating AlN/sapphire using pulsed laser deposition for the n-ZnO and metal organic chemical vapor deposition for the other layers. X-ray diffraction revealed that high crystallographic quality was preserved after the n-ZnO growth. LEDs showed a turn-on voltage of 2.5 V and a room temperature electroluminescence (EL) centered at 510 nm. A blueshift and narrowing of the EL peak with increasing current was attributed to bandgap renormalization. The results indicate that hybrid LED structures could hold the prospect for the development of green LEDs with superior performance. [reprint (PDF)]
 
1.  Electrically pumped photonic crystal distributed feedback quantum cascade lasers
Y. Bai, P. Sung, S.R. Darvish, W. Zhang, A. Evans, S. Slivken, and M. Razeghi
SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 69000A-1-8.-- February 1, 2008 ...[Visit Journal]
We demonstrate electrically pumped, room temperature, single mode operation of photonic crystal distributed feedback (PCDFB) quantum cascade lasers emitting at ~ 4.75 µm. Ridge waveguides of 50 µm and 100 µm width were fabricated with both PCDFB and Fabry-Perot feedback mechanisms. The Fabry-Perot device has a broad emitting spectrum and a broad far-field character. The PCDFB devices have primarily a single spectral mode and a diffraction limited far field characteristic with a full angular width at half-maximum of 4.8 degrees and 2.4 degrees for the 50 µm and 100 µm ridge widths, respectively. [reprint (PDF)]
 
1.  Scaling in back-illuminated GaN avalanche photodiodes
K. Minder, J.L. Pau, R. McClintock, P. Kung, C. Bayram, M. Razeghi and D. Silversmith
Applied Physics Letters, Vol. 91, No. 7, p. 073513-1-- August 13, 2007 ...[Visit Journal]
Avalanche p-i-n photodiodes of various mesa areas were fabricated on AlN templates for back illumination for enhanced performance through hole-initiated multiplication, and the effects of increased area on device performance were studied. Avalanche multiplication was observed in mesa sizes up to 14,063 µm^2 under linear mode operation. Uniform gain and a linear increase of the dark current with area were demonstrated. [reprint (PDF)]
 
1.  Optical Coatings by ion-beam sputtering deposition for long-wave infrared quantum cascade lasers
J. Nguyen, J.S. Yu, A. Evans, S. Slivken and M. Razeghi
Applied Physics Letters, 89 (11)-- September 11, 2006 ...[Visit Journal]
The authors report on the development of high-reflection and multilayer antireflection coatings using ion-beam sputtering deposition for long-wave infrared (λ~9.4 μm) quantum cascade lasers. A metallic high-reflection coating structure using Y2O3 and Au is demonstrated to achieve a high reflectance of 96.70%, and the use of a multilayer anti-reflection coating structure using PbTe and ZnO is demonstrated to achieve a very low reflectance of 1.64%. [reprint (PDF)]
 
1.  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 ...[Visit Journal]
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 (PDF)]
 
1.  Short Wavelength (λ~ 4.3 μm) High-Performance Continuous-Wave Quantum-Cascade Lasers
J.S. Yu, A. Evans, S. Slivken, S.R. Darvish, and M. Razeghi
IEEE Photonics Technology Letters, 17 (6)-- June 1, 2005 ...[Visit Journal]
We report continuous-wave (CW) operation of a 4.3-μm quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-μm-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm2 is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 μm at 80 K to 4.34 μm at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26° and 49° in CW mode, respectively. [reprint (PDF)]
 
1.  4.5 mW Operation of AlGaN-based 267 nm Deep-Ultraviolet Light-Emitting Diodes
A. Yasan, R. McClintock, K. Mayes, D. Shiell, L. Gautero, S.R. Darvish, P. Kung and M. Razeghi
Applied Physics Letters, 83 (23)-- December 8, 2003 ...[Visit Journal]
We demonstrate 4.5 mW output power from AlGaN-based single quantum well ultraviolet light-emitting diodes at a very short wavelength of 267 nm in pulsed operation mode. The output power in continuous-wave mode reaches a value of 165 µW at an injected current of 435 mA. The measurements were done on arrays of four devices flip chip bonded to AlN submounts for thermal management. [reprint (PDF)]
 
1.  Top-emission ultraviolet light-emitting diodes with peak emission at 280 nm
A. Yasan, R. McClintock, K. Mayes, S.R. Darvish, P. Kung, and M. Razeghi
Applied Physics Letters 81 (5)-- July 29, 2002 ...[Visit Journal]
We demonstrate light emission at 280 nm from UV light-emitting diodes consisting of AlInGaN/AlInGaN multiple quantum wells. Turn-on voltage of the devices is ~5 V with a differential resistance of ~40 Ω. The peak emission wavelength redshifts ~1 nm at high injection currents. [reprint (PDF)]
 
1.  Miniaturization: enabling technology for the new millennium
M. Razeghi and H. Mohseni
SPIE International Conference on Solid State Crystals, Zakopane, Poland, -- April 1, 2001 ...[Visit Journal]
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 (PDF)]
 
1.  Pulse Autocorrelation Measurements Based on Two- and Three-Photon Conductivity in a GaN Photodiode
A. Streltsov, K.D. Moll, A. Gaeta, P. Kung, D. Walker, and M. Razeghi
Applied Physics Letters 75 (24)-- December 13, 1999 ...[Visit Journal]
We characterize the performance of a GaN p-i-n photodiode as a nonlinear sensor for second- and third-order femtosecond pulse autocorrelation measurements in the visible and near-infrared regimes, respectively. The two- and three-photon absorption coefficients for GaN are also determined. [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.  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)]
 
1.  Recent advances in III-Nitride materials, characterization and device applications
M. Razeghi, X. Zhang, P. Kung, A. Saxler, D. Walker, K.Y. Lim, and K.S. Kim
SPIE Conference: Solid State Crystals in Optoelectronics and Semiconductor Technology; Proceedings 3179-- October 7, 1996 ...[Visit Journal]
High-quality AlN, GaN, AlGaN have been grown on sapphire substrate by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The x-ray rocking curve of AlN and GaN were 100 arcsecs and 30 arcsecs respectively with Pendelloesung oscillations, which are the best reported to date. GaN with high crystallinity simultaneously exhibited high optical and electrical quality. Photoluminescence linewidth of GaN at 77K was as low as 17 meV, which is the best reported to date. Si-doped GaN had a mobility higher than 300 cm²/V·s. GaN has been also successfully grown on LiGaO2 substrate with LP-MOCVD for the first time. AlGaN for the entire composition range has been grown. These layers exhibited the lowest x-ray FWHM reported to date. The excellent optical quality of these layers have been characterized by room temperature UV transmission and photoluminescence. N-type doping of AlGaN with Si has ben achieved up to 60 percent Al with mobility as high as 78 cm²/V·s. AlxGa1-xN/AlyGa1-yN superlattice with atomically sharp interface have been demonstrated. Optically-pumped stimulated emission in GaN:Ge and GaN:Si has been observed with threshold optical power density as low as 0.4 MW/cm². AlGaN photoconductors with cut-off wavelengths from 200 nm to 365 nm have been achieved for the first time. GaN p-n junction photovoltaic detector with very selective photoresponse have been demonstrated and theoretically modeled. Ti/AlN/Si metal-insulator- semiconductor capacitor with high capacitance-voltage performances at both low and high frequencies and low interface trap level density have been demonstrated for the first time in this material system. [reprint (PDF)]
 
1.  Semiconductor ultraviolet detectors
M. Razeghi and A. Rogalski
SPIE Photonics West '96 Photodetectors: Materials and Devices; Proceedings 2685-- January 27, 1996 ...[Visit Journal]
This paper presents an overview of semiconductor ultraviolet (UV) detectors that are currently available and associated technologies that are undergoing further development. At the beginning, the classification of UV detectors and general requirements imposed on these detectors are presented. Further consideration are restricted to modern semiconductor UV detectors, so the current state-of-the-art of different types of semiconductor UV detectors is presented. Hitherto, the semiconductor UV detectors have been mainly fabricated using Si. Industries such as the aerospace, automotive, petroleum, and others have continuously provided the impetus pushing the development of fringe technologies which are tolerant of increasingly high temperatures and hostile environments. As a result, the main effort are currently directed to a new generation of UV detectors fabricated from wide-band-gap semiconductors between them the most promising are diamond and AlGaN. The latest progress in development of AlGaN UV detectors is finally described in detail. [reprint (PDF)]
 
1.  Second harmonic generation in hexagonal silicon carbide
P.M. Lundquist, W.P. Lin, G.K. Wong, M. Razeghi, and J.B. Ketterson
Applied Physics Letters 66 (15)-- April 10, 1995 ...[Visit Journal]
We report optical second harmonic generation measurements in single crystal α-SiC of polytype 6H. The angular dependence of second harmonic intensity was consistent with two independent nonvanishing second order susceptibility components, as expected for a crystal with hexagonal symmetry. For the fundamental wavelength of 1.064 μm the magnitudes of the two components were determined to be χzzz(2)=±1.2×10−7 and χzxx(2)=∓1.2×10−8 esu. The corresponding linear electro‐optic coefficient computed from this value is rzzz=±100 pm/V. The wavelength dependence of the nonlinear susceptibility was examined for second harmonic wavelengths between the bandgap (400 nm) and the red (700 nm), and was found to be relatively uniform over this region. The refractory nature of this compound and its large nonlinear optical coefficients make it an attractive candidate for high power nonlinear optical waveguide applications. [reprint (PDF)]
 
1.  Well Resolved Room Temperature Photovoltage Spectra of GaAs-GaInP Quantum Wells and Superlattices
Xiaoguang He and Manijeh Razeghi
Applied Physics Letters 62 (6)-- February 8, 1993 ...[Visit Journal]
We report the first well resolved room‐temperature photovoltage spectra due to the sublevel transitions in the GaInP‐GaAs superlattices and multiquantum wells grown by low pressure metalorganic chemical vapor deposition. Sharp well resolved peaks attributed to exciton absorption of the electron‐to‐light hole and electron‐to‐heavy hole have been observed at room temperature. This indicates that GaAs‐GaInP is a promising material for the application of the modulators, optical switches, and optical bistable divices. Satisfactory agreements between experimental measurements and theoretical results have been obtained. These results demonstrate that photovoltage spectroscopy is a simple, but very powerful tool to study quantum confinement structures.   [reprint (PDF)]
 
1.  Ultraviolet avalanche photodiodes
Ryan McClintock ; Manijeh Razeghi
Proc. SPIE 9555, Optical Sensing, Imaging, and Photon Counting: Nanostructured Devices and Applications, 95550B -- August 28, 2015 ...[Visit Journal]
The III-Nitride material system is rapidly maturing; having proved itself as a material for LEDs and laser, and now finding use in the area of UV photodetectors. However, many UV applications are still dominated by the use of photomultiplier tubes (PMT). PMTs are capable of obtaining very high sensitivity using internal electron multiplication gain (typically ~106). It is highly desirable to develop a compact semiconductor-based photodetector capable of realizing this level of sensitivity. In principle, this can be obtained in III-Nitrides by taking advantage of avalanche multiplication under high electric fields – typically 2.7 MV/cm, which with proper design can correspond to an external reverse bias of less than 100 volts. In this talk, we review the current state-of-the-art in III-Nitride solar- and visible-blind APDs, and present our latest results on GaN APDs grown on both conventional sapphire and low dislocation density free-standing c- and m-plane GaN substrates. Leakage current, gain, and single photon detection efficiency (SPDE) of these APDs were compared. The spectral response and Geiger-mode photon counting performance of UV APDs are studied under low photon fluxes, with single photon detection capabilities as much as 30% being demonstrated in smaller devices. Geiger-mode operation conditions are optimized for enhanced SPDE. [reprint (PDF)]
 

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