Center for Quantum Devices - Most Downloaded Journal Articles

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1.	High performance photodiodes based on InAs/InAsSb type-II superlattices for very long wavelength infrared detection A. M. Hoang, G. Chen, R. Chevallier, A. Haddadi, and M. Razeghi Appl. Phys. Lett. 104, 251105 (2014)-- June 23, 2014 ...[Visit Journal] Very long wavelength infrared photodetectors based on InAs/InAsSb Type-II superlattices are demonstrated on GaSb substrate. A heterostructure photodiode was grown with 50% cut-off wavelength of 14.6 μm. At 77 K, the photodiode exhibited a peak responsivity of 4.8 A/W, corresponding to a quantum efficiency of 46% at −300 mV bias voltage from front side illumination without antireflective coating. With the dark current density of 0.7 A/cm², it provided a specific detectivity of 1.4 × 10¹⁰ Jones. The device performance was investigated as a function of operating temperature, revealing a very stable optical response and a background limited performance below 50 K. [reprint (PDF)]
1.	Planar nBn type-II superlattice mid-wavelength infrared photodetectors using zinc ion-implantation Arash Dehzangi, Donghai Wu, Ryan McClintock, Jiakai Li, and Manijeh Razeghi Appl. Phys. Lett. 116, 221103 https://doi.org/10.1063/5.0010273-- June 2, 2020 ...[Visit Journal] In this Letter, we report the demonstration of zinc ion-implantation to realize planar mid-wavelength infrared photodetectors based on type-II InAs/InAs1−xSbx superlattices. At 77 K, the photodetectors exhibit a peak responsivity of 0.68 A/W at 3.35 μm, corresponding to a quantum efficiency of 23.5% under Vb = −80 mV, without anti-reflection coating; these photodetectors have a 100% cutoff wavelength of 4.28 μm. With an R0 × A value of 1.53 × 104 Ω cm2 and a dark current density of 1.23 × 10−6 A/cm2 under an applied bias of −80 mV at 77 K, the photodetectors exhibit a specific detectivity of 9.12 × 1011 cm·Hz1/2/W. [reprint (PDF)]
1.	Monolithic terahertz source Q. Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai and M. Razeghi Nature Photonics \| Research Highlights -- July 31, 2014 ...[Visit Journal] To date, the production of continuous-wave terahertz (THz) sources based on intracavity difference-frequency generation from mid-infrared quantum cascade lasers operating at room temperature has proved elusive. A critical problem is that, to achieve a large nonlinear susceptibility for frequency conversion, the active region of the quantum cascade laser requires high doping, which elevates the lasing threshold current density. Now, Quan-Yong Lu and colleagues from Northwestern University in the USA have overcome this problem and demonstrated a room-temperature continuous-wave THz source based on difference-frequency generation in quantum cascade lasers. They designed quantum-well structures based on In_0.53Ga_0.47As/In_0.52Al_0.48As material system for two mid-infrared wavelengths. The average doping in the active region was about 2.5 × 10¹⁶ cm⁻³. A buried ridge, buried composite distributed-feedback waveguide with the Čerenkov phase-matching scheme was used to reduce the waveguide loss and enhance heat dissipation. As a result, single-mode emission at 3.6 THz was observed at 293 K. The continuous-wave THz power reached 3 μW with a conversion efficiency of 0.44 mW W⁻² from mid-infrared to THz waves. Using a similar device design, a THz peak power of 1.4 mW was achieved in pulse mode. [reprint (PDF)]
1.	Investigation of Enhanced Heteroepitaxy and Electrical Properties in k-Ga2O3 due to Interfacing with β-Ga2O3 Template Layers Junhee Lee, Lakshay Gautam, Ferechteh H. Teherani, Eric V. Sandana, P. Bove, David J. Rogers and Manijeh Razeghi J. Lee, M. Razeghi, Physica Status Solidi A 2023,220, 2200559, https://doi.org/10.1002/pssa.202200559 ...[Visit Journal] Heteroepitaxial k-Ga2O3 films grown by metal-organic chemical vapor deposition (MOCVD) were found to have superior materials and electrical properties thanks to the interfacing with a b-Ga2O3 template layer. k-Ga2O3grown on sapphire has not been able to demonstrate its full potential due to materials imperfections created by strain induced by the lattice mismatch at the interface between the epilayer and the substrate. By adopting a b-Ga2O3 template on a c-sapphire substrate, higher quality k-Ga2O3thin films were obtained, as evidenced by a smoother surface morphology, narrower XRD peaks, and superior electrical performance. The implications of this phenomenon, caused by b-Ga2O3 buffer layer, are already very encouraging for both boosting current device performance and opening up the perspective of novel applications for Ga2O3. [reprint (PDF)]
1.	InAs/InAs_1-xSb_x type-II superlattices for high performance long wavelength infrared detection A. Haddadi , G. Chen , R. Chevallier , A. M. Hoang , and M. Razeghi Appl. Phys. Lett. 105, 121104 (2014)-- September 22, 2014 ...[Visit Journal] High performance long-wavelength infrared nBn photodetectors based on InAs/InAs_1−xSb_x type-II superlattices on GaSb substrate have been demonstrated. The photodetector's 50% cut-off wavelength was ∼10 μm at 77 K. The photodetector with a 6 μm-thick absorption region exhibited a peak responsivity of 4.47 A/W at 7.9 μm, corresponding to a quantum efficiency of 54% at −90 mV bias voltage under front-side illumination and without any anti-reflection coating. With an R × A of 119 Ω·cm² and a dark current density of 4.4 × 10⁻⁴ A/cm² under −90 mV applied bias at 77 K, the photodetector exhibited a specific detectivity of 2.8 × 10¹¹ cm·Hz^1/2·W^-1. [reprint (PDF)]
1.	Growth and Characterization of Very Long Wavelength Type-II Infrared Detectors H. Mohseni, A. Tahraoui, J. Wojkowski, M. Razeghi, W. Mitchel, and A. Saxler SPIE Conference, San Jose, CA, -- January 26, 2000 ...[Visit Journal] We report on the growth and characterization of type-II IR detectors with a InAs/GaSb superlattice active layer in the 15-19 μm wavelength range. The material was grown by molecular beam epitaxy on semi-insulating GaAs substrates. The material was processed into photoconductive detectors using standard photolithography, dry etching, and metalization. The 50 percent cut-off wavelength of the detectors is about 15.5 μm with a responsivity of 90 mA/W at 80 K. The 90 percent-10 percent cut-off energy width of the responsivity is only 17 meV which is an indication of the uniformity of the superlattices. These are the best reported values for type-II superlattices grown on GaAs substrates. [reprint (PDF)]
1.	Room temperature compact THz sources based on quantum cascade laser technology M. Razeghi; Q.Y. Lu; N. Bandyopadhyay; S. Slivken; Y. Bai Proc. SPIE 8846, Terahertz Emitters, Receivers, and Applications IV, 884602 (September 24, 2013)-- November 24, 2013 ...[Visit Journal] We present the high performance THz sources based on intracavity difference-frequency generation from mid-infrared quantum cascade lasers. Room temperature single-mode operation in a wide THz spectral range of 1-4.6 THz is demonstrated from our Čerenkov phase-matched THz sources with dual-period DFB gratings. High THz power up to 215 μW at 3.5 THz is demonstrated via epi-down mounting of our THz device. The rapid development renders this type of THz sources promising local oscillators for many astronomical and medical applications. [reprint (PDF)]
1.	Type-II superlattice-based extended short-wavelength infrared focal plane array with an AlAsSb/GaSb superlattice etch-stop layer to allow near-visible light detection Romain Chevallier, Arash Dehzangi, Abbas Haddadi, and Manijeh Razeghi Optics Letters Vol. 42, Iss. 21, pp. 4299-4302-- October 17, 2017 ...[Visit Journal] A versatile infrared imager capable of imaging the near-visible to the extended short-wavelength infrared (e-SWIR) is demonstrated using e-SWIR InAs/GaSb/AlSb type-II superlattice-based photodiodes. A bi-layer etch-stop scheme consisting of bulk InAs_0.91Sb_0.09 and AlAs_0.1Sb_0.9/GaSb superlattice layers is introduced for substrate removal from the hybridized back-side illuminated photodetectors. The implementation of this new technique on an e-SWIR focal plane array results in a significant enhancement in the external quantum efficiency (QE) in the 1.8–0.8μm spectral region, while maintaining a high QE at wavelengths longer than 1.8μm. Test pixels exhibit 100% cutoff wavelengths of ∼2.1 and ∼2.25μm at 150 and 300K, respectively. They achieve saturated QE values of 56% and 68% at 150 and 300K, respectively, under back-side illumination and without any anti-reflection coating. At 150K, the photodetectors (27μm×27μm area) exhibit a dark current density of 4.7×10⁻⁷ A/cm² under a −50 mV applied bias providing a specific detectivity of 1.77×10¹² cm·Hz^1/2/W. At 300K, the dark current density reaches 6.6×10⁻² A/cm² under −50 mV bias, providing a specific detectivity of 5.17×10⁹ cm·Hz^1/2/W. [reprint (PDF)]
1.	Room temperature quantum cascade laser with ∼ 31% wall-plug efficiency F. Wang, S. Slivken, D. H. Wu, and M. Razeghi AIP Advances 10, 075012-- July 14, 2020 ...[Visit Journal] In this article, we report the demonstration of a quantum cascade laser emitting at λ ≈ 4.9 μm with a wall-plug efficiency of ∼31% and an output power of ∼23 W in pulsed operation at room temperature with 50 cascade stages (Ns). With proper fabrication and packaging, this buried ridge quantum cascade laser with a cavity length of 5 mm delivers more than ∼15 W output power, and its wall-plug efficiency exceeds ∼20% at 100 °C. The experimental results of the lasers are well in agreement with the numerical predictions. [reprint (PDF)]
1.	Sb-based infrared materials and photodetectors for the near room temperature applications J.D. Kim, E. Michel, H. Mohseni, J. Wojkowski, J.J. Lee and M. Razeghi SPIE Conference, San Jose, CA, Vol. 2999, pp. 55-- February 12, 1997 ...[Visit Journal] We report on the growth of InSb, InAsSb, and InTlSb alloys for infrared photodetector applications. The fabrication and characterization of photodetectors based on these materials are also reported. Both photoconductive and photovoltaic devices are investigated. The materials and detector structures were grown on (100) and (111)B semi-insulating GaAs and GaAs coated Si substrates by low pressure metalorganic chemical vapor deposition and solid source molecular beam epitaxy. Photoconductive detectors fabricated from InAsSb and InTlSb have been operated in the temperature range from 77 K to 300 K. The material parameters for photovoltaic device structures have been optimized through theoretical calculations based on fundamental mechanisms. InSb p-i-n photodiodes with 77 K peak responsivities approximately 103 V/W were grown on Si and (111) GaAs substrates. An InAsSb photovoltaic detector with a composition of x equals 0.85 showed photoresponse up to 13 micrometers at 300 K with a peak responsivity of 9.13 X 10-2 V/W at 8 micrometers . The RoA product of InAsSb detectors has been theoretically and experimentally analyzed. [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.	Al_xGa_1−xN-based solar-blind ultraviolet photodetector based on lateral epitaxial overgrowth of AlN on Si substrate E. Cicek, R. McClintock, C. Y. Cho, B. Rahnema, and M. Razeghi Appl. Phys. Lett. 103, 181113 (2013)-- October 30, 2013 ...[Visit Journal] We report on Al_xGa_1−xN-based solar-blind ultraviolet (UV) photodetector (PD) grown on Si(111) substrate. First, Si(111) substrate is patterned, and then metalorganic chemical vapor deposition is implemented for a fully-coalesced ∼8.5 μm AlN template layer via a pulsed atomic layer epitaxial growth technique. A back-illuminated p-i-n PD structure is subsequently grown on the high quality AlN template layer. After processing and implementation of Si(111) substrate removal, the optical and electrical characteristic of PDs are studied. Solar-blind operation is observed throughout the array; at the peak detection wavelength of 290 nm, 625 μm² area PD showed unbiased peak external quantum efficiency and responsivity of ∼7% and 18.3 mA/W, respectively, with a UV and visible rejection ratio of more than three orders of magnitude. Electrical measurements yielded a low-dark current density below 1.6 × 10⁻⁸ A/cm² at 10 V reverse bias. [reprint (PDF)]
1.	Continuous operation of a monolithic semiconductor terahertz source at room temperature Q. Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai, and M. Razeghi Appl. Phys. Lett. 104, 221105 (2014)-- June 3, 2014 ...[Visit Journal] We demonstrate room temperature continuous wave THz sources based on intracavity difference-frequency generation from mid-infrared quantum cascade lasers. Buried ridge, buried composite distributed-feedback waveguide with Čerenkov phase-matching scheme is used to reduce the waveguide loss and enhance the heat dissipation for continuous wave operation. Continuous emission at 3.6 THz with a side-mode suppression ratio of 20 dB and output power up to 3 μW are achieved, respectively. THz peak power is further scaled up to 1.4 mW in pulsed mode by increasing the mid-infrared power through increasing the active region doping and device area. [reprint (PDF)]
1.	High Power Mid-Infrared Quantum Cascade Lasers Grown on GaAs Steven Slivken and Manijeh Razeghi Photonics 2022, 9(4), 231 (COVER ARTICLE) ...[Visit Journal] The motivation behind this work is to show that InP-based intersubband lasers with high power can be realized on substrates with significant lattice mismatch. This is a primary concern for the integration of mid-infrared active optoelectronic devices on low-cost photonic platforms, such as Si. As evidence, an InP-based mid-infrared quantum cascade laser structure was grown on a GaAs substrate, which has a large (4%) lattice mismatch with respect to InP. Prior to laser core growth, a metamorphic buffer layer of InP was grown directly on a GaAs substrate to adjust the lattice constant. Wafer characterization data are given to establish general material characteristics. A simple fabrication procedure leads to lasers with high peak power (>14 W) at room temperature. These results are extremely promising for direct quantum cascade laser growth on Si substrates. [reprint (PDF)]
1.	Development of high power, InP-based quantum cascade lasers on alternative epitaxial platforms Steven Slivken, Nirajman Shrestha, Manijeh Razeghi Proc. of SPIE Vol. 12895, Quantum Sensing and Nano Electronics and Photonics XX, 1289503 (28 January - 1 February 2024, San Francisco) doi: 10.1117/12.3009335 ...[Visit Journal] In this talk, challenges and solutions associated with the monolithic, epitaxial integration of mid- and longwave- infrared, InP-based quantum cascade lasers on GaAs and Si wafers will be discussed. Initial results, including room temperature, high power, and continuous wave operation, will be described. [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)]

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