Center for Quantum Devices - Most Downloaded Journal Articles

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2.	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.	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)]
1.	Growth and characterization of InAs/GaSb photoconductors for long wavelength infrared range H. Mohseni, E. Michel, J. Sandven, M. Razeghi, W. Mitchel, and G. Brown Applied Physics Letters 71 (10)-- September 8, 1997 ...[Visit Journal] In this letter we report the molecular beam epitaxial growth and characterization of InAs/GaSb superlattices grown on semi-insulating GaAs substrates for long wavelength infrared detectors. Photoconductive detectors fabricated from the superlattices showed photoresponse up to 12 µm and peak responsivity of 5.5 V/W with Johnson noise limited detectivity of 1.33 × 10⁹ cm·Hz^½/W at 10.3 µm at 78 K. [reprint (PDF)]
1.	Mid-wavelength infrared high operating temperature pBn photodetectors based on type-II InAs/InAsSb superlattice Donghai Wu, Jiakai Li, Arash Dehzangi, and Manijeh Razeghi AIP Advances 10, 025018-- February 11, 2020 ...[Visit Journal] A high operating temperature mid-wavelength infrared pBn photodetector based on the type-II InAs/InAsSb superlattice on a GaSb substrate has been demonstrated. At 150 K, the photodetector exhibits a peak responsivity of 1.48 A/W, corresponding to a quantum efficiency of 47% at −50 mV applied bias under front-side illumination, with a 50% cutoff wavelength of 4.4 μm. With an R×A of 12,783 Ω·cm² and a dark current density of 1.16×10⁻⁵A/cm² under −50 mV applied bias, the photodetector exhibits a specific detectivity of 7.1×10¹¹ cm·Hz^½/W. At 300 K, the photodetector exhibits a dark current density of 0.44 A/cm²and a quantum efficiency of 39%, resultingin a specific detectivity of 2.5×10⁹ cm·Hz^½/W. [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.	Techniques for High-Quality SiO₂ Films J. Nguyen and M. Razeghi SPIE Conference, January 25-29, 2007, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices IV, Vol. 6479, p. 64791K-1-8-- January 29, 2007 ...[Visit Journal] We report on the comparison of optical, structural, and electrical properties of SiO₂ using plasma-enhanced chemical vapor deposition and ion-beam sputtering deposition. High-quality, low-temperature deposition of SiO₂ by ion-beam sputtering deposition is shown to have lower absorption, smoother and more densely packed films, a lower amount of fixed oxide charges, and a lower trapped-interface density than SiO₂ by plasma-enhanced chemical vapor deposition. This high-quality SiO₂ is then demonstrated as an excellent electrical and mechanical surface passivation layer on Type-II InAs/GaSb photodetectors [reprint (PDF)]
1.	Generation-recombination and trap-assisted tunneling in long wavelength infrared minority electron unipolar photodetectors based on InAs/GaSb superlattice F. Callewaert, A.M. Hoang, and M. Razeghi Applied Physics Letters, 104, 053508 (2014)-- February 6, 2014 ...[Visit Journal] A long wavelength infrared minority electron unipolar photodetector based on InAs/GaSb type-II superlattices is demonstrated. At 77 K, a dark current of 3 × 10⁻⁵ A/cm² and a differential resistance-area of 3 700 Ω·cm² are achieved at the turn-on bias, with a 50%-cutoff of 10.0 μm and a specific detectivity of 6.2 × 10¹¹ Jones. The dark current is fitted as a function of bias and temperature using a model combining generation-recombination and trap-assisted tunneling. Good agreement was observed between the theory and the experimental dark current. [reprint (PDF)]
1.	Recent Advances in InAs/GaSb Superlattices for Very Long Wavelength Infrared Detection G.J. Brown, F. Szmulowicz, K. Mahalingam, S. Houston, Y. Wei, A. Gin and M. Razeghi SPIE Conference, San Jose, CA, Vol. 4999, pp. 457-- January 27, 2003 ...[Visit Journal] New infrared (IR) detector materials with high sensitivity, multi-spectral capability, improved uniformity and lower manufacturing costs are required for numerous long and very long wavelength infrared imaging applications. One materials system has shown great theoretical and, more recently, experimental promise for these applications: InAs/In_xGa_1-xSb type-II superlattices. In the past few years, excellent results have been obtained on photoconductive and photodiode samples designed for infrared detection beyond 15 microns. The infrared properties of various compositions and designs of these type-II superlattices have been studied. The infrared photoresponse spectra are combined with quantum mechanical modeling of predicted absorption spectra to provide insight into the underlying physics behind the quantum sensing in these materials. Results for superlattice photodiodes with cut-off wavelengths as long as 25 microns are presented. [reprint (PDF)]
1.	2.4 W room temperature continuous wave operation of distributed feedback quantum cascade lasers Q.Y. Lu, Y. Bai, N. Bandyopadhyay, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 98, No. 18, p. 181106-1-- May 4, 2011 ...[Visit Journal] We demonstrate high power continuous-wave room-temperature operation surface-grating distributed feedback quantum cascade lasers at 4.8 μm. High power single mode operation benefits from a combination of high-reflection and antireflection coatings. Maximum single-facet continuous-wave output power of 2.4 W and peak wall plug efficiency of 10% from one facet is obtained at 298 K. Single mode operation with a side mode suppression ratio of 30 dB and single-lobed far field without beam steering is observed. [reprint (PDF)]
1.	Persistent photoconductivity and the quantized Hall effect in In0.53Ga0.47As/InP heterostructures H. P. Wei; D. C. Tsui; M. Razeghi H. P. Wei, D. C. Tsui, M. Razeghi; Persistent photoconductivity and the quantized Hall effect in In0.53Ga0.47As/InP heterostructures. Appl. Phys. Lett. 15 September 1984; 45 (6): 666–668.-- September 15, 1984 ...[Visit Journal] A persistent photoconductivity is observed in the transport of the high mobility two‐dimensional electron gas in In0.53Ga0.47 As/InP heterostructures. Low field Hall measurements from 300 to 4.2 K and the quantized Hall effect in the high field limit are studied with radiation from visible and infrared light‐emitting diodes. Our results demonstrate conclusively that the effect is due to photogeneration of electron‐hole pairs in the heterostructure and trapping of holes in the In0.53Ga0.47 As. [reprint (PDF)]
1.	Comparison of the Physical Properties of GaN Thin Films Deposited on (0112) and (0001) Sapphire Substrates C.J. Sun and M. Razeghi Applied Physics Letters 63 (7)-- August 16, 1993 ...[Visit Journal] A direct comparison of the physical properties of GaN thin films is made as a function of the choice of substrate orientations. Gallium nitride single crystals were grown on (0001) and (0112) sapphire substrates by metalorganic chemical vapor deposition. Better crystallinity with fine ridgelike facets is obtained on the (0112) sapphire. Also lower carrier concentration and higher mobilities indicate both lower nitrogen vacancies and less oxygen incorporation on the (0112) sapphire. The results of this study show better physical properties of GaN thin films achieved on (0112) sapphire. [reprint (PDF)]
1.	Inductively coupled plasma etching and processing techniques for type-II InAs/GaSb superlattices infrared detectors toward high fill factor focal plane arrays E.K. Huang, B.M. Nguyen, D. Hoffman, P.Y. Delaunay and M. Razeghi SPIE Proceedings, San Jose, CA Volume 7222-0Z-- January 26, 2009 ...[Visit Journal] A challenge for Type-II InAs/GaSb superlattice (T2SL) photodetectors is to achieve high fill factor, high aspect ratio etching for third generation focal plane arrays (FPAs). Initially, we compare the morphological and electrical results of single element T2SL photodiodes after BCl₃/Ar inductively coupled plasma (ICP) and electron cyclotron resonance (ECR) dry etching. Using a Si₃N₄ hard mask, ICP-etched structures exemplify greater sidewall verticality and smoothness, which are essential toward the realization of high fill factor FPAs. ICP-etched single element devices with SiO₂ passivation that are 9.3 µm in cutoff wavelength achieved vertical sidewalls of 7.7 µm in depth with a resistance area product at zero bias of greater than 1,000 Ω·cm² and maximum differential resistance in excess of 10,000 Ω·cm² at 77 K. By only modifying the etching technique in the fabrication steps, the ICP-etched photodiodes showed an order of magnitude decrease in their dark current densities in comparison to the ECR-etched devices. Finally, high aspect ratio etching is demonstrated on mutli-element arrays with 3 µm-wide trenches that are 11 µm deep. [reprint (PDF)]
1.	Stranski-Krastanov growth of InGaN quantum dots emitting in green spectra C. Bayram and M. Razeghi Applied Physics A: Materials Science and Processing, Vol. 96, No. 2, p. 403-408-- August 1, 2009 ...[Visit Journal] Self-assembled InGaN quantum dots (QDs) were grown on GaN templates by metalorganic chemical vapor deposition. 2D–3D growth mode transition through Stranski–Krastanov mode was observed via atomic force microscopy. The critical thickness for In_0.67Ga_0.33N QDs was determined to be four monolayers. The effects of growth temperature, deposition thickness, and V/III ratio on QD formation were examined. The capping of InGaN QDs with GaN was analyzed. Optimized InGaN quantum dots emitted in green spectra at room temperature. [reprint (PDF)]
1.	Extended electrical tuning of quantum cascade lasers with digital concatenated gratings S. Slivken, N. Bandyopadhyay, Y. Bai, Q. Y. Lu, and M. Razeghi Appl. Phys. Lett. 103, 231110 (2013)-- December 6, 2013 ...[Visit Journal] In this report, the sampled grating distributed feedback laser architecture is modified with digital concatenated gratings to partially compensate for the wavelength dependence of optical gain in a standard high efficiency quantum cascade laser core. This allows equalization of laser threshold over a wide wavelength range and demonstration of wide electrical tuning. With only two control currents, a full tuning range of 500 nm (236 cm⁻¹) has been demonstrated. Emission is single mode, with a side mode suppression of >20 dB. [reprint (PDF)]
1.	High Quality Type-II InAs/GaSb Superlattices with Cutoff Wavelength ~3.7 µm Using Interface Engineering Y. Wei, J. Bae, A. Gin, A. Hood, M. Razeghi, G.J. Brown, and M. Tidrow Journal of Applied Physics, 94 (7)-- October 1, 2003 ...[Visit Journal] We report the most recent advance in the area of Type-II InAs/GaSb superlattices that have cutoff wavelength of ~3.7 µm. With Ga_xIn_1–x type interface engineering techniques, the mismatch between the superlattices and the GaSb (001) substrate has been reduced to <0.1%. There is no evidence of dislocations using the best examination tools of x-ray, atomic force microscopy, and transmission electron microscopy. The full width half maximum of the photoluminescence peak at 11 K was ~4.5 meV using an Ar+ ion laser (514 nm) at fluent power of 140 mW. The integrated photoluminescence intensity was linearly dependent on the fluent laser power from 2.2 to 140 mW at 11 K. The temperature-dependent photoluminescence measurement revealed a characteristic temperature of one T1 = 245 K at sample temperatures below 160 K with fluent power of 70 mW, and T1 = 203 K for sample temperatures above 180 K with fluent power of 70 and 420 mW. [reprint (PDF)]
1.	Room temperature quantum cascade lasers with 27% wall plug efficiency Y. Bai, N. Bandyopadhyay, S. Tsao, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 98, No. 18, p. 181102-1-- May 3, 2011 ...[Visit Journal] Using the recently proposed shallow-well design, we demonstrate InP based quantum cascade lasers (QCLs) emitting around 4.9 μm with 27% and 21% wall plug efficiencies in room temperature (298 K) pulsed and continuous wave (CW) operations, respectively. The laser core consists of 40 QCL-stages. The highest cw efficiency is obtained from a buried-ridge device with a ridge width of 8 μm and a cavity length of 5 mm. The front and back facets are antireflection and high-reflection coated, respectively. The maximum single facet cw power at room temperature amounts to 5.1 W. [reprint (PDF)]
1.	Recent advances in antimonide-based gap-engineered Type-II superlattices material system for 2 and 3 colors infrared imagers Manijeh. Razeghi, Abbas Haddadi, Arash Dehzangi, Romain Chevallier, and Thomas Yang Proceedings of SPIE 10177, Infrared Technology and Applications XLIII, 1017705-- May 9, 2017 ...[Visit Journal] InAs/InAs_1-xSb_x/AlAs_1-xSb_x type-II superlattices (T2SLs) is a system of multi-interacting quantum wells. Since its introduction, this material system has drawn a lot of attention especially for infrared detection. In recent years, InAs/InAs_1- xSb_x/AlAs_1-xSb_x T2SL material system has experienced incredible improvements in material quality, device structure designs and device fabrication process which elevated the performances of T2SL-based photodetectors to a comparable level to the state-of-the-art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). In this paper, we will present the current status of InAs/InAs_1-xSb_x/AlAs_1-xSb_x T2SL-based photodetectors for detection in different infrared regions, from short-wavelength (SWIR) to long-wavelength (LWIR) infrared, and the future outlook of this material system. [reprint (PDF)]
1.	Recent advances in IR semiconductor laser diodes and future trends M. Razeghi; Y. Bai; N. Bandyopadhyay; B. Gokden; Q.Y. Lu; S. Slivken Photonics Society Summer Topical Meeting Series, IEEE [6000041], pp. 55-56 (2011)-- July 18, 2011 ...[Visit Journal] The wall plug efficiency of the mid-infrared quantum cascade laser in room temperature continuous wave (cw) operation is brought to 21%, with a maximum output power of 5.1 W. Using a surface grating distributed feedback (DFB) approach, we demonstrated 2.4 W single mode output in room temperature cw operation. With a photonic crystal distributed feedback (PCDFB) design, we achieved single mode spectrum and close to diffraction limited far field with a room temperature high peak power of 34 W. [reprint (PDF)]
1.	Cubic Phase GaN on Nano-grooved Si (100) via Maskless Selective Area Epitaxy Bayram, C., Ott, J. A., Shiu, K.-T., Cheng, C.-W., Zhu, Y., Kim, J., Razeghi, M. and Sadana, D. K. Adv. Funct. Mater. 2014-- April 1, 2014 ...[Visit Journal] A method of forming cubic phase (zinc blende) GaN (referred as c-GaN) on a CMOS-compatible on-axis Si (100) substrate is reported. Conventional GaN materials are hexagonal phase (wurtzite) (referred as h-GaN) and possess very high polarization fields (∼MV/cm) along the common growth direction of <0001>. Such large polarization fields lead to undesired shifts (e.g., wavelength and current) in the performance of photonic and vertical transport electronic devices. The cubic phase of GaN materials is polarization-free along the common growth direction of <001>, however, this phase is thermodynamically unstable, requiring low-temperature deposition conditions and unconventional substrates (e.g., GaAs). Here, novel nano-groove patterning and maskless selective area epitaxy processes are employed to integrate thermodynamically stable, stress-free, and low-defectivity c-GaN on CMOS-compatible on-axis Si. These results suggest that epitaxial growth conditions and nano-groove pattern parameters are critical to obtain such high quality c-GaN. InGaN/GaN multi-quantum-well structures grown on c-GaN/Si (100) show strong room temperature luminescence in the visible spectrum, promising visible emitter applications for this technology. [reprint (PDF)]
1.	Highly temperature insensitive quantum cascade lasers Y. Bai, N. Bandyopadhyay, S. Tsao, E. Selcuk, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 97, No. 25-- December 20, 2010 ...[Visit Journal] An InP based quantum cascade laser (QCL) heterostructure emitting around 5 μm is grown with gas-source molecular beam epitaxy. The QCL core design takes a shallow-well approach to maximize the characteristic temperatures, T(0) and T(1), for operations above room temperature. A T(0) value of 383 K and a T(1) value of 645 K are obtained within a temperature range of 298–373 K. In room temperature continuous wave operation, this design gives a single facet output power of 3 W and a wall plug efficiency of 16% from a device with a cavity length of 5 mm and a ridge width of 8 μm. [reprint (PDF)]
1.	Bias-selectable dual-band mid-/long-wavelength infrared photodetectors based on InAs/InAs_1−xSb_x type-II superlattices A. Haddadi, R. Chevallier, G. Chen, A. M. Hoang, and M. Razeghi Applied Physics Letters 106 , 011104-- January 8, 2015 ...[Visit Journal] A high performance bias-selectable mid-/long-wavelength infrared photodetector based on InAs/InAs_1−xSb_x type-II superlattices on GaSb substrate has been demonstrated. The mid- and long-wavelength channels' 50% cut-off wavelengths were ∼5.1 and ∼9.5 μm at 77 K. The mid-wavelength channel exhibited a quantum efficiency of 45% at 100 mV bias voltage under front-side illumination and without any anti-reflection coating. With a dark current density of 1 × 10⁻⁷ A/cm² under 100 mV applied bias, the mid-wavelength channel exhibited a specific detectivity of 8.2 × 10¹² cm·Hz^½·W^-1 at 77 K. The long-wavelength channel exhibited a quantum efficiency of 40%, a dark current density of 5.7 × 10⁻⁴ A/cm² under −150 mV applied bias at 77 K, providing a specific detectivity value of 1.64 × 10¹¹ cm·Hz^½·W^-1. [reprint (PDF)]
1.	Widely Tunable, Single-Mode, High-Power Quantum Cascade Lasers M. Razeghi, B. Gokden, S. Tsao, A. Haddadi, N. Bandyopadhyay, and S. Slivken SPIE Proceedings, Intergreated Photonics: Materials, Devices and Applications, SPIE Microtechnologies Symposium, Prague, Czech Republic, April 18-20, 2011, Vol. 8069, p. 806905-1-- May 31, 2011 ...[Visit Journal] We demonstrate widely tunable high power distributed feedback quantum cascade laser array chips that span 190 nm and 200 nm from 4.4 um to 4.59 um and 4.5 um to 4.7 um respectively. The lasers emit single mode with a very narrow linewidth and side mode suppression ratio of 25 dB. Under pulsed operation power outputs up to 1.85 W was obtained from arrays with 3 mm cavity length and up to 0.95 W from arrays with 2 mm cavity length at room temperature. Continuous wave operation was also observed from both chips with 2 mm and 3 mm long cavity arrays up to 150 mW. The cleaved size of the array chip with 3 mm long cavities was around 4 mm x 5 mm and does not require sensitive external optical components to achieve wide tunability. With their small size and high portability, monolithically integrated DFB QCL Arrays are prominent candidates of widely tunable, compact, efficient and high power sources of mid-infrared radiation for gas sensing. [reprint (PDF)]
1.	Evaluating the size-dependent quantum efficiency loss in a SiO₂-Y₂O₃hybrid gated type-II InAs/GaSb long-infrared photodetector array G. Chen , A. M. Hoang , and M. Razeghi Applied Physics Letters 104 , 103509 (2014)-- March 14, 2014 ...[Visit Journal] Growing Y₂O₃ on 20 nm SiO₂ to passivate a 11 μm 50% cut-off wavelength long-wavelength infrared type-II superlattice gated photodetector array reduces its saturated gate bias (VG_sat ) to −7 V. Size-dependent quantum efficiency (QE) losses are evaluated from 400 μm to 57 μm size gated photodiode. Evolution of QE of the 57 μm gated photodiode with gate bias and diode operation bias reveals different surface recombination mechanisms. At 77 K and VG,sat , the 57 μm gated photodiode exhibits QE enhancement from 53% to 63%, and it has 1.2 × 10⁻⁵ A/cm² dark current density at −200 mV, and a specific detectivity of 2.3 × 10¹² Jones. [reprint (PDF)]
1.	Demonstration of shortwavelength infrared photodiodes based on type-II InAs/GaSb/AlSb superlattices A.M. Hoang, G. Chen, A. Haddadi, S. Abdollahi Pour, and M. Razeghi Applied Physics Letters, Vol. 100, No. 21, p. 211101-1-- May 21, 2012 ...[Visit Journal] We demonstrate the feasibility of the InAs/GaSb/AlSb type-II superlattice photodiodes operating at the short wavelength infrared regime below 3 μm. An n-i-p type-II InAs/GaSb/AlSb photodiode was grown with a designed cut-off wavelength of 2 μm on a GaSb substrate. At 150 K, the photodiode exhibited a dark current density of 5.6 × 10⁻⁸ A/cm² and a front-side-illuminated quantum efficiency of 40.3%, providing an associated shot noise detectivity of 1.0 × 10¹³ Jones. The uncooled photodiode showed a dark current density of 2.2 × 10⁻³ A/cm² and a quantum efficiency of 41.5%, resulting in a detectivity of 1.7 × 10¹⁰ Jones [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)]

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