Center for Quantum Devices - Most Downloaded Journal Articles

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2.	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 ...[Visit Journal] 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 (PDF)]
2.	Geiger-mode operation of ultraviolet avalanche photodiodes grown on sapphire and free-standing GaN substrates E. Cicek, Z. Vashaei, R. McClintock, C. Bayram, and M. Razeghi Applied Physics Letters, Vol. 96, No. 26, p. 261107 (2010);-- June 28, 2010 ...[Visit Journal] GaN avalanche photodiodes (APDs) were grown on both conventional sapphire and low dislocation density free-standing (FS) c-plane GaN substrates. Leakage current, gain, and single photon detection efficiency (SPDE) of these APDs were compared. At a reverse-bias of 70 V, APDs grown on sapphire substrates exhibited a dark current density of 2.7×10⁻⁴ A/cm² whereas APDs grown on FS-GaN substrates had a significantly lower dark current density of 2.1×10⁻⁶ A/cm². Under linear-mode operation, APDs grown on FS-GaN achieved avalanche gain as high as 14 000. Geiger-mode operation conditions were studied for enhanced SPDE. Under front-illumination the 625 μm² area APD yielded a SPDE of 13% when grown on sapphire substrates compared to more than 24% when grown on FS-GaN. The SPDE of the same APD on sapphire substrate increased to 30% under back-illumination—the FS-GaN APDs were only tested under front illumination due to the thick absorbing GaN substrate. [reprint (PDF)]
2.	Growth and Optimization of GaInAsP/InP Material System for Quantum Well Infrared Photodetector Applications M. Erdtmann, J. Jiang, A. Matlis, A. Tahraoui, C. Jelen, M. Razeghi, and G. Brown SPIE Conference, San Jose, CA, -- January 26, 2000 ...[Visit Journal] Multi-quantum well structures of Ga_xIn_1-xAs_yP_1-y were grown by metalorganic chemical vapor deposition for the fabrication of quantum well IR photodetectors. The thickness and composition of the wells was determined by high-resolution x-ray diffraction and photoluminescence experiments. The intersubband absorption spectrum of the Ga_0.47In_0.53As/InP, Ga_0.38In_0.62As_0.80P_0.20 (1.55 μm)/InP, and Ga_0.27In_0.73As_0.57P_0.43 (1.3 μm))/InP quantum wells are found to have cutoff wavelengths of 9.3 μm, 10.7 micrometers , and 14.2 μm respectively. These wavelengths are consistent with a conduction band offset to bandgap ratio of approximately 0.32. Facet coupled illumination responsivity and detectivity are reported for each composition. [reprint (PDF)]
2.	High Performance Type-II InAs/GaSb Superlattice Photodiodes H. Mohseni, Y. Wei, and M. Razeghi SPIE Conference, San Jose, CA, -- January 22, 2001 ...[Visit Journal] 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 λ_c 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 (PDF)]
2.	Evaluation of the Band Offsets of GaAs-GaInP Multilayers by Electroreflectance Razeghi M., D. Yang, J.W. Garland, Z. Zhang, D. Xue SPIE Proceedings, Vol. 1676, pp. 130-- January 1, 1992 ...[Visit Journal] We report the first band offset measurement of GaAs/Ga_0.51In_0.49P multiquantum wells and superlattices by electrolyte electroreflectance spectroscopy. The conduction and valence band discontinuities (Delta) Ec equals 159 ± 4 meV and (Delta) Ev equals 388 ± 6 meV have been measured. The values found for the conduction band, heavy-hole and light-hole masses in the GaInP barriers and GaAs wells and for the split-off well mass are in excellent agreement with the literature. The intraband, intersubband transition energies, which are important for III - V infrared detection devices, also were directly measured. [reprint (PDF)]
2.	High performance InAs quantum dot infrared photodetectors (QDIP) on InP by MOCVD W. Zhang, H. Lim, M. Taguchi, S. Tsao, J. Szafraniec, B. Movaghar, M. Razeghi, and M. Tidrow SPIE Conference, Jose, CA, Vol. 5732, pp. 326-- January 22, 2005 ...[Visit Journal] Inter-subband detectors such as quantum well infrared photodetectors (QWIP) have been widely used in infrared detection. Quantum dot infrared photodetectors (QDIPs) have been predicted to have better performance than QWIPs including higher operation temperature and normal incidence detection. Here we report our recent results of InAs QDIP grown on InP substrate by low-pressure metalorganic chemical vapor deposition (MOCVD). The device structures consist of multiple stacks of InAs quantum dots with InP barriers. High detectivities in the range of 10¹⁰cm·Hz^1/2/W were obtained at 77K. The measurements at higher temperatures show better temperature dependent performance than QWIP. However, the performances of QDIPs are still far from the expected. One of the reasons is the low quantum efficiency due to the low fill factor of quantum dots layer. Resonant cavity enhanced QDIP has been studied to increase the quantum efficiency. Different schemes of mirrors using free carrier plasma and distributed Bragg reflector are discussed. [reprint (PDF)]
2.	Investigation of the factors influencing nanostructure array growth by PLD towards reproducible wafer-scale growth Vinod E. Sandana; David. J. Rogers; Ferechteh Hosseini Teherani; Philippe Bove; Manijeh Razeghi physica status solidi (a) Applications and Materials Science. Volume 211, Issue 2, pages 449–454, (February 2014)-- January 14, 2014 ...[Visit Journal] The growth of catalyst-free ZnO nanostructure arrays on silicon (111) substrates by pulsed laser deposition was investigated. Without an underlayer, randomly oriented, micron-scale structures were obtained. Introduction of a c-axis oriented ZnO underlayer resulted in denser arrays of vertically oriented nanostructures with either tapering, vertical-walled or broadening forms, depending on background Ar pressure. Nanostructure pitch seemed to be determined by underlayer grain size while nanostructure widths could be narrowed from ∼100–500 to ∼10–50 nm by a 50 °C increase in growth temperature. A dimpled underlayer topography correlated with the moth-eye type arrays while a more granular surface was linked to vertically walled nanocolumns. Between-wafer reproducibility was demonstrated for both moth-eye and vertical nanocolumn arrays. Broadening nanostructures proved difficult to replicate, however. Full 2 inch wafer coverage was obtained by rastering the target with the laser beam. [reprint (PDF)]
2.	Broad area photonic crystal distributed feedback quantum cascade lasers emitting 34 W at λ ~ 4.36 μm B. Gokden, Y. Bai, N. Bandyopadhyay, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 97, No. 13, p. 131112-1-- September 27, 2010 ...[Visit Journal] We demonstrate room temperature, high power, single mode, and diffraction limited operation of a two dimensional photonic crystal distributed feedback quantum cascade laser emitting at 4.36 μm. Total peak power up to 34 W is observed from a 3 mm long laser with 400 μm cavity width at room temperature. Far-field profiles have M2 figure of merit as low as 2.5. This device represents a significant step toward realization of spatially and spectrally pure broad area high power quantum cascade lasers. [reprint (PDF)]
2.	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·Hz^½/W at room temperature and 1.5×10¹³ cm·Hz^½/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)]
2.	High Performance Quantum Cascade Lasers at λ ~ 6 μm M. Razeghi, S. Slivken, J. Yu, A. Evans, and J. David Microelectronics Journal, 34 (5-8)-- May 1, 2003 ...[Visit Journal] This talk will focus on the recent efforts at the Center for Quantum Devices to deliver a high average power quantum cascade laser source at λ ~6 μm. Strain-balancing is used to reduce leakage for these shorter wavelength quantum cascade lasers. Further, the effect of reducing the doping in the injector is explored relative to the threshold current density and maximum average output power. Lastly, to demonstrate more of the potential of these devices, epilayer down bonding is explored as a technique to significantly enhance device performance. [reprint (PDF)]
2.	High Power, Room Temperature InP-Based Quantum Cascade Laser Grown on Si Steven Slivken and Manijeh Razeghi Journal of Quantum Electronics, Vol. 58, No. 6, 2300206 ...[Visit Journal] We report on the realization of an InP-based long wavelength quantum cascade laser grown on top of a silicon substrate. This demonstration first required the development of an epitaxial template with a smooth surface, which combines two methods of dislocation filtering. Once wafer growth was complete, a lateral injection buried heterostructure laser geometry was employed for efficient current injection and low loss. The laser emits at a wavelength of 10.8 μm and is capable of operation above 373 K, with a high peak power (>4 W) at room temperature. Laser threshold behavior with temperature is characterized by a T0 of 178 K. The far field beam shape is single lobed, showing fundamental transverse mode operation. [reprint (PDF)]
2.	Continuous-wave operation of λ ~ 4.8 µm quantum-cascade lasers at room temperature A. Evans, J.S. Yu, S. Slivken, and M. Razeghi Applied Physics Letters, 85 (12)-- September 20, 2004 ...[Visit Journal] Continuous-wave (cw) operation of quantum-cascade lasers emitting at λ~4.8 µm is reported up to a temperature of 323 K. Accurate control of layer thickness and strain-balanced material composition is demonstrated using x-ray diffraction. cw output power is reported to be in excess of 370 mW per facet at 293 K, and 38 mW per facet at 323 K. Room-temperature average power measurements are demonstrated with over 600 mW per facet at 50% duty cycle with over 300 mW still observed at 100% (cw) duty cycle. [reprint (PDF)]
2.	High-performance short-wavelength infrared photodetectors based on type-II InAs/InAs_1-xSb_x/AlAs_1-xSb_x superlattices M. Razeghi, A. Haddadi, X. V. Suo, S. Adhikary, P. Dianat, R. Chevallier, A. M. Hoang, A. Dehzangi Proc. SPIE 9819, Infrared Technology and Applications XLII, 98190A -- May 20, 2016 ...[Visit Journal] We present a high-performance short-wavelength infrared n-i-p photodiode, whose structure is based on type-II superlattices with InAs/InAs_1-xSb_x/AlAs_1-xSb_x on GaSb substrate. At room temperature (300K) with front-side illumination, the device shows the peak responsivity of 0.47 A/W at 1.6mm, corresponding to 37% quantum efficiency at zero bias. At 300K, the device has a 50% cut-off wavelength of ~1.8mm. For −50mV applied bias at 300 K the photodetector has dark current density of 9.6x10^-5 A/cm² and RxA of 285 Ω•cm², and it revealed a detectivity of 6.45x10¹⁰ cm•Hz^½/W. Dark current density reached to 1.3x10^-8 A/cm² at 200 K, with 36% quantum efficiency which leads to the detectivity value of 5.66x10¹² cm•Hz^½/W. [reprint (PDF)]
2.	Growth of InAsSb Alloys on GaAs and Si Substrates for Uncooled Infrared Photodetector Applications J.D. Kim, H. Mohseni, J.S. Wojkowski, J.J. Lee and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 ...[Visit Journal] In this paper, we report on the growth and characterization of InAsSb alloys on GaAs and Si substrates for uncooled infrared photodetector applications. The fabrication and characterization of photodetectors from the grown layers are also reported. The photovoltaic and photoconductive devices were grown on (100) GaAs and Si substrates, respectively, using molecular beam epitaxy (MBE). The composition of InAs>sub>1-xSb_x layers was 0.95 in both cases and cut-off wavelength of 7-8 μm has been obtained. At 300 K, the photovoltaic detectors on GaAs substrates resulted in a sharp cut-off wavelength of 7.5 μm with a peak responsivity as high as 0.32 V/W at 6.5 micrometer. For the photoconductive detectors on Si substrates, cut-off wavelength of 8 μm has been observed with a responsivity of 6.3x10^-2 V/W at 7 μm under an electric field of 420 V/m. [reprint (PDF)]
2.	Aluminum gallium nitride short-period superlattices doped with magnesium A. Saxler, W.C. Mitchel, P. Kung and M. Razeghi Applied Physics Letters 74 (14)-- April 9, 1999 ...[Visit Journal] Short-period superlattices consisting of alternating layers of GaN:Mg and AlGaN:Mg were grown by low-pressure organometallic vapor phase epitaxy. The electrical properties of these superlattices were measured as a function of temperature and compared to conventional AlGaN:Mg layers. It is shown that the optical absorption edge can be shifted to shorter wavelengths while lowering the acceptor ionization energy by using short-period superlattice structures instead of bulk-like AlGaN:Mg. [reprint (PDF)]
2.	InP-based quantum-dot infrared photodetectors with high quantum efficiency and high temperature imaging S. Tsao, H. Lim, H. Seo, W. Zhang and M. Razeghi IEEE Sensors Journal, Vol. 8, No. 6, p. 936-941-- June 1, 2008 ...[Visit Journal] We report a room temperature operating InAs quantum-dot infrared photodetector grown on InP substrate. The self-assembled InAs quantum dots and the device structure were grown by low-pressure metalorganic chemical vapor depositon. The detectivity was 6 x 10¹⁰cm·Hz^1/2·W^-1 at 150 K and a bias of 5 V with a peak detection wavelength around 4.0 micron and a quantum efficiency of 48%. Due to the low dark current and high responsivity, a clear photoresponse has been observed at room temperature. A 320 x 256 middle wavelength infrared focal plane array operating at temperatures up to 200 K was also demonstrated. The focal plane array had 34 mA/W responsivity, 1.1% conversion efficiency, and noise equivalent temperature difference of 344 mK at 120 K operating temperature. [reprint (PDF)]
2.	Thermal imaging based on high-performance InAs/InP quantum-dot infrared photodetector operating at high temperature M. Razeghi; H. Lim; S. Tsao; H. Seo; W. Zhang Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS.15-16:[4382251] (2007).-- October 21, 2007 ...[Visit Journal] We report a room temperature operating and high-performance InAs quantum-dot infrared photodetector on InP substrate and thermal imaging of 320times256 focal plane array based on this device up to 200 K. [reprint (PDF)]
2.	High performance bias-selectable three-color Short-wave/Mid-wave/Long-wave Infrared Photodetectors based on Type-II InAs/GaSb/AlSb superlattices Anh Minh Hoang, Arash Dehzangi, Sourav Adhikary, & Manijeh Razeghi Nature Scientific Reports 6, Article number: 24144-- April 7, 2016 ...[Visit Journal] We propose a new approach in device architecture to realize bias-selectable three-color shortwave-midwave-longwave infrared photodetectors based on InAs/GaSb/AlSb type-II superlattices. The effect of conduction band off-set and different doping levels between two absorption layers are employed to control the turn-on voltage for individual channels. The optimization of these parameters leads to a successful separation of operation regimes; we demonstrate experimentally three-color photodiodes without using additional terminal contacts. As the applied bias voltage varies, the photodiodes exhibit sequentially the behavior of three different colors, corresponding to the bandgap of three absorbers. Well defined cut-offs and high quantum efficiency in each channel are achieved. Such all-in-one devices also provide the versatility of working as single or dual-band photodetectors at high operating temperature. With this design, by retaining the simplicity in device fabrication, this demonstration opens the prospect for three-color infrared imaging. [reprint (PDF)]
2.	Broadband monolithically-tunable quantum cascade lasers Wenjia Zhou, Ryan McClintock, Donghai Wu, Steven Slivken, Manijeh Razeghi Proc. SPIE 10540, Quantum Sensing and Nano Electronics and Photonics XV, 105400A-- January 26, 2018 ...[Visit Journal] Mid-infrared lasers, emitting in the spectral region of 3-12 μm that contain strong characteristic vibrational transitions of many important molecules, are highly desirable for spectroscopy sensing applications. High efficiency quantum cascade lasers have been demonstrated with up to watt-level output power in the mid-infrared region. However, the wide wavelength tuning, which is critical for spectroscopy applications, is still largely relying on incorporating external gratings, which have stability issues. Here, we demonstrate the development a monolithic, widely tunable quantum cascade laser source emitting between 6.1 and 9.2 μm through an on-chip integration of a sampled grating distributed feedback tunable laser array with a beam combiner. A compact tunable laser system was built to drive the individual lasers within the array and coordinate the driving of the laser array to produce desired wavelength. A broadband spectral measurement (520cm^-1) of methane shows excellent agreement with Fourier transform infrared spectrometer measurement. Further optimizations have led to high performance monolithic tunable QCLs with up to 65 mW output while delivering fundamental mode outputs. [reprint (PDF)]
2.	Molecular Beam Epitaxial Growth of High Quality InSb E. Michel, G. Singh, S. Slivken, C. Besikci, P. Bove, I. Ferguson, and M. Razeghi Applied Physics Letters 65 (26)-- December 26, 1994 ...[Visit Journal] In this letter we report on the growth of high quality InSb by molecular beam epitaxy that has been optimized using reflection high energy electron diffraction. A 4.8 µm InSb layer grown on GaAs at a growth temperature of 395 °C and a III/V incorporation ratio of 1:1.2 had an x-ray rocking curve of 158 arcsec and a Hall mobility of 92,300 cm²·V⁻¹ at 77 K. This is the best material quality obtained for InSb nucleated directly onto GaAs reported to date. [reprint (PDF)]
2.	Demonstration of negative differential resistance in GaN/AlN resonant tunneling didoes at room temperature Z. Vashaei, C. Bayram and M. Razeghi Journal of Applied Physics, Vol. 107, No. 8, p. 083505-- April 15, 2010 ...[Visit Journal] GaN/AlN resonant tunneling diodes (RTD) were grown by metal-organic chemical vapor deposition (MOCVD) and negative differential resistance with peak-to-valley ratios as high as 2.15 at room temperature was demonstrated. Effect of material quality on RTDs’ performance was investigated by growing RTD structures on AlN, GaN, and lateral epitaxial overgrowth GaN templates. Our results reveal that negative differential resistance characteristics of RTDs are very sensitive to material quality (such as surface roughness) and MOCVD is a suitable technique for III-nitride-based quantum devices. [reprint (PDF)]
2.	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)]
2.	p-doped GaAs/Ga_0.51In_0.49P quantum well intersub-band photodetectors J. Hoff, X. He, M. Erdtmann, E. Bigan, M. Razeghi, and G.J. Brown Journal of Applied Physics 78 (3)-- August 1, 1995 ...[Visit Journal] Lattice‐matched p-doped GaAs–Ga_0.51In_0.49P quantum well intersub‐band photodetectors with three different well widths have been grown on GaAs substrates by metal‐organic chemical‐vapor deposition and fabricated into mesa structures. The photoresponse cutoff wavelength varies between 3.5 and 5.5 μm by decreasing the well width from 50 down to 25 Å. Dark current measurements as a function of temperature reveal activation energies for thermionic emission that closely correspond to measured cutoff wavelengths. Experimental results are in reasonable agreement with Kronig–Penney calculations. [reprint (PDF)]
2.	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)]
2.	Watt level performance of quantum cascade lasers in room temperature continuous wave operation at λ ∼ 3.76 μm N. Bandyopadhyay, Y. Bai, B. Gokden, A. Myzaferi, S. Tsao, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 97, No. 13-- September 27, 2010 ...[Visit Journal] An InP-based quantum cascade laser heterostructure emitting at 3.76 μm is grown with gas-source molecular beam epitaxy. The laser core is composed of strain balanced In_0.76Ga_0.24As/In_0.26Al_0.74As. Pulsed testing at room temperature exhibits a low threshold current density (1.5 kA/cm²) and high wall plug efficiency (10%). Room temperature continuous wave operation gives 6% wall plug efficiency with a maximum output power of 1.1 W. Continuous wave operation persists up to 95 °C. [reprint (PDF)]

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