Center for Quantum Devices - Most Downloaded Journal Articles

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6.	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)]
6.	Solar-Blind Deep UV Avalanche Photodetectors Using Reduced Area Epitaxy Lakshay Gautam , Junhee Lee, Michael Richards, and Manijeh Razeghi , Lakshay Gautam, Manijeh Razeghi, IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 59, NO. 6, 10.1109/JQE.2023.3325254 ...[Visit Journal] We report high gain avalanche photodetectors operating in the deep UV wavelength regime. The high gain was leveraged through reduced area epitaxy by patterning AlN on Sapphire substrate. This helps in a substantial reduction of crack formation due to overgrowth on individually isolated AlN mesas. Reproducible gain on the order of 105 was reported for multiple diodes in different areas of 320 × 256 focal plane array. [reprint (PDF)]
6.	Theoretical investigation of minority carrier leakage of high-power 0.8 μm InGaAsP/InGaP/GaAs laser diodes J. Diaz, I. Eliashevich, H.J. Yi, M. Stanton, and M. Razeghi Applied Physics Letters 65 (18)-- October 31, 1994 ...[Visit Journal] We report a theoretical model that accurately describes the effects of minority carrier leakage from the InGaAsP waveguide into InGaP cladding layers in high‐power aluminum-free 0.8 μm InGaAsP/InGaP/GaAs separate confinement heterostructure lasers. Current leakage due to the relatively low band‐gap discontinuity between the active region and the InGaP barrier can be eliminated by employing laser diodes with cavity length longer than 500 μm. Experimental results for lasers grown by low-pressure metalorganic chemical vapor deposition are in excellent agreement with the theoretical model. [reprint (PDF)]
5.	Stable single mode terahertz semiconductor sources at room temperature M. Razeghi 2011 International Semiconductor Device Research Symposium, ISDRS [6135180] (2011).-- December 7, 2011 ...[Visit Journal] Terahertz (THz) range is an area of the electromagnetic spectra which has lots of applications but it suffers from the lack of simple working devices which can emit THz radiation, such as the high performance mid-infrared (mid-IR) quantum cascade lasers (QCLs) based on InP technology. The applications for the THz can be found in astronomy and space research, biology imaging, security, industrial inspection, etc. Unlike THz QCLs based on the fundamental oscillators, which are limited to cryogenic operations, semiconductor THz sources based on nonlinear effects of mid-IR QCLs do not suffer from operating temperature limitations, because mid-IR QCLs can operate well above room temperature. THz sources based on difference frequency generation (DFG) utilize nonlinear properties of asymmetric quantum structures, such as QCL structures. [reprint (PDF)]
5.	EPR investigation of Gd3+ and Eu2+ in the α- and β-phases of lead phosphate M. RAZEGHI, J. P. BUISSON, and B. HOULIE M. RAZEGHI et al.: EPR Investigation of Gd3+ and Eu2+ in Lead Phosphate phys. stat. sol. (b) 96, 283 (1979-- September 1, 1979 ...[Visit Journal] The X-band EPR spectra of Gd3+and Eu2+diluted in Pb3(P04)2crystals are studied. Lead phos-phate exhibits a ferroelastic phase transition a t 180 “C and the EPR spectra obtained in eachphase differ from each other. The spectra are very complex because the zero field splitting hasthe same order of magnitude as the Zeeman term. The spin Hamiltonian parameters and theenergy levels are computed. “Forbidden” or “missing” transitions and line intensities can beexplained. [reprint (PDF)]
5.	Room temperature continuous wave operation of quantum cascade lasers with 12.5% wall plug efficiency Y. Bai, S. Slivken, S.R. Darvish, and M. Razeghi Applied Physics Letters, Vol. 93, No. 2, p. 021103-1-- July 14, 2008 ...[Visit Journal] An InP based quantum cascade laser heterostructure emitting at 4.6 µm was grown with gas-source molecular beam epitaxy. The wafer was processed into a conventional double-channel ridge waveguide geometry with ridge widths of 19.7 and 10.6 µm without semi-insulating InP regrowth. An uncoated, narrow ridge device with a 4.8 mm cavity length was epilayer down bonded to a diamond submount and exhibits 2.5 W maximum output power with a wall plug efficiency of 12.5% at room temperature in continuous wave operation. [reprint (PDF)]
5.	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)]
5.	Very Long Wavelength GaAs/GaInP Quantum Well Infrared Photodetectors C. Jelen, S. Slivken, G.J. Brown, and M. Razeghi SPIE Conference, San Jose, CA, -- February 12, 1997 ...[Visit Journal] We demonstrate long wavelength quantum well infrared photodetectors with GaAs quantum wells and GaInP barriers grown using gas-source molecular beam epitaxy. Wafers were grown with varying well widths. The optimum well width was 75 angstrom, which resulted in a detection peak at 13 μm and a cutoff wavelength of 15 μm. Dark current measurements of the samples with 15 μm cutoff wavelength show low dark current densities. The dark current characteristics have been investigated as a function of temperature and electron density in the well and compared to a model which takes into account thermionic emission and thermally assisted tunneling. The model is used to extract a saturation velocity of 1.5 x 10⁵ cm/s for electrons. The photoelectron lifetime before recapture has been deduced from this carrier velocity and photoconductive gain measurements. The lifetime is found to be approximately 5 ps. Preliminary focal plane array imaging is demonstrated. [reprint (PDF)]
5.	High-Power (~9 μm) Quantum Cascade Lasers S. Slivken, Z. Huang, A. Evans, and M. Razeghi Virtual Journal of Nanoscale Science and Technology 5 (22)-- June 3, 2002 ...[Visit Journal][reprint (PDF)]
5.	High power, low divergent, substrate emitting quantum cascade ring laser in continuous wave operation D. H. Wu and M. Razeghi APL Materials 5, 035505-- March 21, 2017 ...[Visit Journal] We demonstrate a surface grating coupled substrate emitting quantum cascade ring laser with high power room temperature continuous wave operation at 4.64 μm μm . A second order surface metal/semiconductor distributed-feedback grating is used for in-plane feedback and vertical out-coupling. A device with 400 μm μm radius ring cavity exhibits an output power of 202 mW in room temperature continuous wave operation. Single mode operation with a side mode suppression ratio of 25 dB is obtained along with a good linear tuning with temperature. The far field measurement exhibits a low divergent concentric ring beam pattern with a lobe separation of ∼0.34°, which indicates that the device operates in fundamental mode (n = 1). [reprint (PDF)]
5.	Development of Quantum Cascade Lasers for High Peak Output Power and Low Threshold Current Density S. Slivken and M. Razeghi Solid State Electronics 46-- January 1, 2002 ...[Visit Journal] Design and material optimization are used to both decrease the threshold current density and increase the output power for quantum cascade lasers. Waveguides are designed to try and minimize free-carrier and surface-plasmon absorption. Excellent material characterization is also presented, showing excellent control over layer thickness, interface quality, and doping level. Experiments are done to both optimize the injector doping level and to maximize the output power from a single aperture. At 300 K, a threshold current density as low as 1.8 kA/cm² is reported, along with peak powers of approximately 2.5 W. Strain-balanced lasers are also demonstrated at λnot, vert, similar5 μm, exhibiting threshold current densities<300 A/cm² at 80 K. These values represent the state-of-the-art for mid-infrared lasers with λ>4 μm [reprint (PDF)]
5.	Quantum Hall liquid-to-insulator transition in In_1-xGa_xAs/InP heterostructures W. Pan, D. Shahar, D.C. Tsui, H.P. Wei, and M. Razeghi Physical Review B 55 (23)-- June 15, 1997 ...[Visit Journal] We report a temperature- and current-scaling study of the quantum Hall liquid-to-insulator transition in an In_1-xGa_xAs/InP heterostructure. When the magnetic field is at the critical field B_c, ρ_xx=0.86h/e². Furthermore, the transport near B_c scales as \|B- Bc\|T^-κ with κ=0.45±0.05, and as \|B- Bc\|I^-b with b=0.23±0.05. The latter can be due to phonon emission in a dirty piezoelectric medium, or can be the consequence of critical behavior near B_c, within which z=1.0±0.1 and ν=2.1±0.3 are obtained from our data. [reprint (PDF)]
5.	Toward realization of small-size dual-band long-wavelength infrared photodetectors based on InAs/GaSb/AlSb type-II superlattices Romain Chevallier, Abbas Haddadi, Manijeh Razeghi Solid-State Electronics 136, pp. 51-54-- June 20, 2017 ...[Visit Journal] In this study, we demonstrate 12 × 12 µm² high-performance, dual-band, long-wavelength infrared (LWIR) photodetectors based on InAs/GaSb/AlSb type-II superlattices. The structure consists of two back-to-back heterojunction photodiodes with 2 µm-thick p-doped absorption regions. High quality dry etching combined with SiO₂ passivation results in a surface resistivity value of 7.9 × 10⁵ Ω·cm for the longer (red) channel and little degradation of the electrical performance. The device reaches dark current density values of 4.5 × 10⁻⁴ A/cm² for the longer (red) and 1.3 × 10⁻⁴ A/cm² for the shorter (blue) LWIR channels at quantum efficiency saturation. It has 50% cut-off wavelengths of 8.3 and 11.2 µm for the blue and red channel, respectively, at 77 K in back-side illumination configuration and exhibits quantum efficiencies of 37% and 29%, respectively. This results in specific detectivity values of 2.5 × 10¹¹ cm·Hz^½/W and 1.3 × 10¹¹ cm·Hz^½/W at 77 K. [reprint (PDF)]
5.	Mid-wavelength infrared heterojunction phototransistors based on type-II InAs/AlSb/GaSb superlattices A. Haddadi, S. Adhikary, A. Dehzangi, and M. Razeghi Applied Physics Letters 109, 021107-- July 12, 2016 ...[Visit Journal] A mid-wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate has been demonstrated. Near a wavelength of 4 μm saturated optical gains of 668 and 639 at 77 and 150 K, respectively, are demonstrated over a wide dynamic range. At 150 K, the unity optical gain collector dark current density and DC current gain are 1 × 10⁻³ A/cm² and 3710, respectively. This demonstrates the potential for use in high-speed applications. In addition, the phototransistor exhibits a specific detectivity value that is four times higher compared with a state-of-the-art type-II superlattice-based photodiode with a similar cut-off wavelength at 150 K. [reprint (PDF)]
5.	Room Temperature Terahertz and Frequency Combs Based on Intersubband Quantum Cascade Laser Diodes: History and Future e Manijeh Razeghi , and Quanyong Lu Manijeh Razeghi, and Quanyong Lu Room Temperature Terahertz and Frequency Combs Based on Intersubband Quantum Cascade Laser Diodes: History and Futur Photonics 2025, 12(1), 79; ...[Visit Journal] : The year 2024 marks the 30-year anniversary of the quantum cascade laser (QCL), which is becoming the leading laser source in the mid-infrared (mid-IR) range. Since the first demonstration, QCL has undergone tremendous development in terms of the output power, wall plug efficiency, spectral coverage, wavelength tunability, and beam quality. Owing to its unique intersubband transition and fast gain features, QCL possesses strong nonlinearities that makes it an ideal platform for nonlinear photonics like terahertz (THz) difference frequency generation and direct frequency comb generation via fourwave mixing when group velocity dispersion is engineered. The feature of broadband, high-power, and low-phase noise of QCL combs is revolutionizing mid-IR spectroscopy and sensing by offering a new tool measuring multi-channel molecules simultaneously in the µs time scale. While THz QCL difference frequency generation is becoming the only semiconductor light source covering 1–5 THz at room temperature. In this paper, we will introduce the latest research from the Center for Quantum Devices at Northwestern University and briefly discuss the history of QCL, recent progress, and future perspective of QCL research, especially for QCL frequency combs, room temperature THz QCL difference frequency generation, and major challenges facing QCL in the future. [reprint (PDF)]
5.	Demonstration of long wavelength infrared Type-II InAs/InAs_1-xSb_x superlattices photodiodes on GaSb substrate grown by metalorganic chemical vapor deposition D. H. Wu, A. Dehzangi, Y. Y. Zhang, M. Razeghi Applied Physics Letters 112, 241103-- June 12, 2018 ...[Visit Journal] We report the growth and characterization of long wavelength infrared type-II InAs/InAs_1−xSb_x superlattices photodiodes with a 50% cut-off wavelength at 8.0 μm on GaSb substrate grown by metalorganic chemical vapor deposition. At 77 K, the photodiodes exhibited a differential resistance at zero bias (R₀A) 8.0 Ω·cm², peak responsivity of 1.26 A/W corresponding to a quantum efficiency of 21%. A specific detectivity of 5.4×10¹⁰ cm·Hz^1/2/W was achieved at 7.5 μm. [reprint (PDF)]
5.	Back-illuminated solar-blind photodetectors for imaging applications R. McClintock, A. Yasan, K. Mayes, P. Kung, and M. Razeghi SPIE Conference, Jose, CA, Vol. 5732, pp.175-- January 22, 2005 ...[Visit Journal] Back-illuminated solar-blind ultraviolet p-i-n photodetectors and focal plane arrays are investigated. We initially study single-pixel devices and then discuss the hybridization to a read-out integrated circuit to form focal plane arrays for solar-blind UV imaging. [reprint (PDF)]
5.	Combined resonant tunneling and rate equation modeling of terahertz quantum cascade lasers Zhichao Chen , Andong Liu, Dong Chang , Sukhdeep Dhillon , Manijeh Razeghi , Feihu Wang Journal of Applied Physics, 135, 115703 ...[Visit Journal] Terahertz (THz) quantum cascade lasers (QCLs) are technologically important laser sources for the THz range but are complex to model. An efficient extended rate equation model is developed here by incorporating the resonant tunneling mechanism from the density matrix formalism, which permits to simulate THz QCLs with thick carrier injection barriers within the semi-classical formalism. A self-consistent solution is obtained by iteratively solving the Schrödinger-Poisson equation with this transport model. Carrier-light coupling is also included to simulate the current behavior arising from stimulated emission. As a quasi-ab initio model, intermediate parameters such as pure dephasing time and optical linewidth are dynamically calculated in the convergence process, and the only fitting parameters are the interface roughness correlation length and height. Good agreement has been achieved by comparing the simulation results of various designs with experiments, and other models such as density matrix Monte Carlo and non-equilibrium Green’s function method that, unlike here, require important computational resources. The accuracy, compatibility, and computational efficiency of our model enables many application scenarios, such as design optimization and quantitative insights into THz QCLs. Finally, the source code of the model is also provided in the supplementary material of this article for readers to repeat the results presented here, investigate and optimize new designs. [reprint (PDF)]
5.	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)]
5.	The importance of band alignment in VLWIR type-II InAs/GaSb heterodiodes containing the M-structure barrier D. Hoffman, B.M. Nguyen, E.K. Huang, P.Y. Delaunay, S. Bogdanov, P. Manukar, M. Razeghi, and V. Nathan SPIE Proceedings, San Jose, CA Volume 7222-15-- January 26, 2009 ...[Visit Journal] The Type-II InAs/GaSb superlattice photon detector is an attractive alternative to HgCdTe photodiodes and QWIPS. The use of p+ - pi - M - N+ heterodiode allows for greater flexibility in enhancing the device performance. The utilization of the Empirical Tight Binding method gives the band structure of the InAs/GaSb superlattice and the new M- structure (InAs/GaSb/AlSb/GaSb) superlattice allowing for the band alignment between the binary superlattice and the M- superlattice to be determined and see how it affects the optical performance. Then by modifying the doping level of the M- superlattice an optimal level can be determined to achieve high detectivity, by simultaneously improving both photo-response and reducing dark current for devices with cutoffs greater than 14.5 µm. [reprint (PDF)]
4.	Impact of scaling base thickness on the performance of heterojunction phototransistors Arash Dehzangi, Abbas Haddadi, Sourav Adhikary, and Manijeh Razeghi Nanotechnology 28, 10LT01-- February 2, 2017 ...[Visit Journal] In this letter we report the effect of vertical scaling on the optical and electrical performance of mid-wavelength infrared heterojunction phototransistors based on type-II InAs/GaSb/AlSb superlattices. The performance of devices with different base thickness was compared as the base was scaled from 60 down to 40 nm. The overall optical performance shows enhancement in responsively, optical gain, and specific detectivity upon scaling the base width. The saturated responsivity for devices with 40 nm bases reaches 8,845 and 9,528 A/W at 77 and 150 K, respectively, which is almost five times greater than devices with 60 nm bases. The saturated optical gain for devices with 40 nm bases is measured as 2,760 at 77 K and 3,081 at 150 K. The devices with 40 nm bases also exhibit remarkable enhancement in saturated current gain, with 17,690 at 77 K, and 19,050 at 150 K. [reprint (PDF)]
4.	Defects in Organometallic Vapor-Phase Epitaxy-Grown GaInP Layers Feng S.L., Bourgoin J.C., Omnes F., and Razeghi M. Applied Physics Letters 59 (8), p. 941-- May 28, 1991 ...[Visit Journal] Non-intentionally doped metalorganic vapor‐phase epitaxy Ga_1−x InxP layers, having an alloy composition (x = 0.49) corresponding to a lattice matched to GaAs, grown by metalorganic chemical vapor deposition, have been studied by capacitance‐voltage and deep-level transient spectroscopy techniques. They are found to exhibit a free‐carrier concentration at room temperature of the order of 10¹⁵ cm⁻³. Two electron traps have been detected. The first one, at 75 meV below the conduction band, is in small concentration (∼10¹³ cm⁻³) while the other, at about 0.9 eV and emitting electrons above room temperature, has a concentration in the range 10¹⁴–10¹⁵ cm⁻³. [reprint (PDF)]
4.	Optical Absorption and Photoresponse in fully Quaternary p-type Quantum Well Detectors J. Hoff, C. Jelen, S. Slivken, G.J. Brown, and M. Razeghi SPIE Photonics West '96 Photodetectors: Materials and Devices; Proceedings 2685-- January 27, 1996 ...[Visit Journal] Acceptor doped, non-strained aluminum-free Quantum Well Intersubband Photodetectors lattice matched to GaAs with Ga_0.79In_0.21As_0.59P_0.41 wells and Ga_0.62In_0.38As_0.22P_0.78 barriers have been demonstrated on semi-insulating GaAs substrates. These devices which operate at normal incidence demonstrate a unique spectral response which extends from approximately 2 μm up to 10 μm. To explain such a broad spectral shape, a detailed theoretical analysis based on the 8 x 8 Kane Hamiltonian was necessary to probe all aspect of optical absorption. The results of this analysis revealed that spectral shape results from the influence of the Spin Split-off band on the band structure and the optical matrix. [reprint (PDF)]
4.	High-Average-Power, High-Duty-Cycle (~6 μm) Quantum Cascade Lasers S. Slivken, A. Evans, J. David, and M. Razeghi Virtual Journal of Nanoscience & Technology 9-- December 9, 2002 ...[Visit Journal][reprint (PDF)]
4.	Quantum Dot Intersubband Photodetectors C. Jelen, M. Erdtmann, S. Kim, and M. Razeghi SPIE Conference, San Jose, CA, -- January 22, 2001 ...[Visit Journal] Quantum dots are recognized as very promising candidates for the fabrication of intersubband photodetectors in the infrared spectral range. At present, material quality is making rapid progress and some devices have been demonstrated. Examples of mid-infrared quantum dot intersubband photodetectors are presented along with device design and data analysis. Nonetheless, the performance of these devices remains less than comparable quantum well intersubband photodetectors due to difficulties in controlling the quantum dot size and distribution during epitaxy. [reprint (PDF)]

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