Center for Quantum Devices - Most Downloaded Journal Articles

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14.	Type-II InAs/GaSb/AlSb superlatticebased heterojunction phototransistors: back to the future Abbas Haddadi, Arash Dehzangi, Romain Chevallier, Thomas Yang, Manijeh Razeghi Proc. SPIE 10540, Quantum Sensing and Nano Electronics and Photonics XV- Page-1054004-1-- January 26, 2018 ...[Visit Journal] Most of reported HPTs in literatures are based on InGaAs compounds that cover NIR spectral region. However, InGaAs compounds provide limited cut-off wavelength tunability. In contrast, type-II superlattices (T2SLs) are a developing new material system with intrinsic advantages such as great flexibility in bandgap engineering, low growth and manufacturing cost, high-uniformity, auger recombination suppression, and high carrier effective mass that are becoming an attractive candidate for infrared detection and imaging from short-wavelength infrared to very long wavelength infrared regime. We present the recent advancements in T2SL-based heterojunction phototransistors in e– SWIR, MWIR and LWIR spectral ranges. A mid-wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate has been demonstrated. Then, we present the effect of vertical scaling on the optical and electrical performance of heterojunction phototransistors, where the performance of devices with different base width was compared as the base was scaled from 60 down to 40 nm. [reprint (PDF)]
14.	Engineering Multi-Section Quantum Cascade Lasers for Broadband Tuning Steven Slivken and Manijeh Razeghi Photonics 3, 41-- June 27, 2016 ...[Visit Journal] In an effort to overcome current limitations to electrical tuning of quantum cascade lasers, a strategy is proposed which combines heterogeneous quantum cascade laser gain engineering with sampled grating architectures. This approach seeks to not only widen the accessible spectral range for an individual emitter, but also compensate for functional non-uniformity of reflectivity and gain lineshapes. A trial laser with a dual wavelength core is presented which exhibits electroluminescence over a 750 cm⁻¹ range and discrete single mode laser emission over a 700 cm⁻¹ range. Electrical tuning over 180 cm⁻¹ is demonstrated with a simple sampled grating design. A path forward to even wider tuning is also described using more sophisticated gain and grating design principles. [reprint (PDF)]
14.	Internal Stress Around Micropipes in 6H-SiC Substrates H. Ohsato, T. Kato, T. Okuda and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 ...[Visit Journal] 6H-SiC single crystals are expected to be suitable substrates for thin film growth of the wide bandgap semiconductor (GaN, because it has a small lattice mismatch with GaN. Moreover, SiC single crystals are also expected for high-power and high- temperature electric applications because of its wide band gap, high breakdown voltage, high thermal conductivity and high temperature stability. Single crystals with large size used for electronic devices can be grown on seed crystals only by the modified Lely method based on sublimation deposition. But, single crystals have serious defects so called micropipes. These micropipes penetrate almost along the [001] direction. The internal strain around micropipes was investigated using the polarizing optical microscope for the purpose of clarifying the formation mechanisms and decreasing the amount of micropipes. A special interference figure was found around a micropipe under the crossed polars on the polarizing microscope. In this work, the special interference figure around micropipes due to internal stress was explained, and the magnitude and distribution of the stress was measured by means of photoelasticity and the mapping of Raman spectra. [reprint (PDF)]
14.	ZnO Thin Films & Nanostructures for Emerging Optoelectronic Applications D.J. Rogers, F. Hosseini Teherani, V.E. Sandana, and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7605, p. 76050K-1-- January 27, 2010 ...[Visit Journal] ZnO-based thin films and nanostructures grown by PLD for various emerging optoelectronic applications. AZO thin films are currently displacing ITO for many TCO applications due to recent improvements in attainable AZO conductivity combined with processing, cost and toxicity advantages. Advances in the channel mobilities and Id on/off ratios in ZnO-based TTFTs have opened up the potential for use as a replacement for a-Si in AM-OLED and AM-LCD screens. Angular-dependent specular reflection measurements of self-forming, moth-eye-like, nanostructure arrays grown by PLD were seen to have <0.5% reflectivity over the whole visible spectrum for angles of incidence between 10 and 60 degrees. Such nanostructures may be useful for applications such as AR coatings on solar cells. Compliant ZnO layers on mismatched/amorphous substrates were shown to have potential for MOVPE regrowth of GaN. This approach could be used as a means to facilitate lift-off of GaN-based LEDs from insulating sapphire substrates and could allow the growth of InGaN-based solar cells on cheap substrates. The green gap in InGaN-based LEDs was combated by substituting low Ts PLD n-ZnO for MOCVD n-GaN in inverted hybrid heterojunctions. This approach maintained the integrity of the InGaN MQWs and gave LEDs with green emission at just over 510 nm. Hybrid n-ZnO/p-GaN heterojunctions were also seen to have the potential for UV (375 nm) EL, characteristic of ZnO NBE emission. This suggests that there was significant hole injection into the ZnO and that such LEDs could profit from the relatively high exciton binding energy of ZnO. [reprint (PDF)]
14.	Etching of ZnO Towards the Development of ZnO Homostructure LEDs K. Minder, F.H. Teherani, D. Rogers, C. Bayram, R. McClintock, P. Kung, and M. Razeghi SPIE Conference, January 25-29, 2007, San Jose, CA Proceedings – Zinc Oxide Materials and Devices II, Vol. 6474, p. 64740Q-1-6-- January 29, 2007 ...[Visit Journal] Although ZnO has recently gained much interest as an alternative to the III-Nitride material system, the development of ZnO based optoelectonic devices is still in its infancy. Significant material breakthroughs in p-type doping of ZnO thin films and improvements in crystal growth techniques have recently been achieved, making the development of optoelectonic devices possible. First, a survey of current ZnO processing methods is presented, followed by the results of our processing research. [reprint (PDF)]
14.	Recent Advances in LWIR Type-II InAs/GaSb Superlattice Photodetectors and Focal Plane Arrays at the Center for Quantum Devices M. Razeghi, D. Hoffman, B.M. Nguyen, P.Y. Delaunay, E.K. Huang, M.Z. Tidrow, and V. Nathan IEEE Proceedings, Vol. 97, No. 6, p. 1056-1066-- June 1, 2009 ...[Visit Journal] In recent years, Type-II InAs/GaSb superlattice photo-detectors have experienced significant improvements in material quality, structural designs, and imaging applications. They now appear to be a possible alternative to the state-of-the-art HgCdTe (MCT) technology in the long and very long wavelength infrared regimes. At the Center for Quantum Devices, we have successfully realized very high quantum efficiency, very high dynamic differential resistance R₀A - product LWIR Type – II InAs/GaSb superlattice photodiodes with efficient surface passivation techniques. The demonstration of high quality LWIR Focal Plane Arrays that were 100 % fabricated in - house reaffirms the pioneer position of this university-based laboratory. [reprint (PDF)]
14.	Recent progress of widely tunable, CW THz sources based QCLs at room temperature Manijeh Razeghi Terahertz Science and Technology, Vol.10, No.4, pp. 87-151-- December 7, 2017 ...[Visit Journal] The THz spectral region is of significant interest to the scientific community, but is one of the hardest regions to access with conventional technology. A wide range of compelling new applications are initiating a new revolution in THz technology, especially with regard to the development of compact and versatile devices for THz emission and detection. In this article, recent advances with regard to III-V semiconductor optoelectronics are explored with emphasis on how these advances will lead to the next generation of THz component technology [reprint (PDF)]
14.	EPR Investigations of a Structural Phase Change in Lead Phosphate M. RAZEG M. RAZEGHI: EPR Investigations of a Structural Phase Change, phys. stat. sol. (b) 108, 175 (1981)-- April 10, 2010 ...[Visit Journal] The temperature dependence of the EPR line width of the Mn2+ and Gd3+ in Pb,(PO,), is investigated from -270 to 500 "C. At the first-order ferroelastic transition point (180 "C), an abrupt change in the fine-structure splitting as well as in the resonance line width is observed. Various contributions to fine structure D and E parameters of Mn2+ and Gd3+ are computed, using a point-multipole model. For temperatures near to Tc the correlation time of the fluctuations is estimated to be greater than Die Temperaturabhangigkeit der EPR-Linienbreite von Mn2+,'und Gd3+ in Pb,(PO,), wird zwischen -270 und 500 "C untersucht. Am ferroelastischen vbergangspunkt erster Ordnung (180 "C) wird eine abrupte Anderung der Feinstrukturaufspaltung sowie der Linienbreite der Resonanzlinien beobachtet. Verschiedene Beitrage zu den Feinstrukturparametern D und E von Mn2+ und Gd3+ werden mittels eines Punkt-Multipol-Modells berechnet. Fur Temperaturen in der Nahe von T, wird die Korrelationszeit der Fluktuationen eu groI3er als s. s bestimmt. [reprint (PDF)]
14.	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)]
14.	Sb-based third generation at Center for Quantum Devices Razeghi, Manijeh SPIE Proceedings Volume 11407, Infrared Technology and Applications XLVI; 114070T-- April 23, 2020 ...[Visit Journal] Sb-based III-V semiconductors are a promising alternative to HgCdTe. They can be produced with a similar bandgap to HgCdTe, but take advantage of the strong bonding between group III and group V elements which leads to very stable materials, good radiation hardness, and high uniformity. In this paper, we will discuss the recent progress of our research and present the main contributions of the Center for Quantum Devices to the Sb-based 3th generation imagers. [reprint (PDF)]
14.	Improved performance of IR photodetectors with 3D gap engineering J. Piotrowski and M. Razeghi Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995 ...[Visit Journal] The ultimate signal-to-noise performance of the semiconductor photodetector is limited by the statistical fluctuations of the thermal generation and recombination rates in photodetector material. Cooling is an effective but impractical way of suppression of the thermal processes. The performance of uncooled detectors can be improved by minimizing the thermal generation and recombination rates and reducing the actual volume of photodetector. This can be realized in 3D heterostructure devices. In these devices, the incident radiation is absorbed in small regions of narrow gap semiconductor, buried in wide gap volume and supplied with wide gap electric contacts and radiation concentrators. The practical near room-temperature 1 - 12 μm IR heterostructure photodetectors are reported. The devices are based on variable gap Hg_1-xCd_xTe. The 3D heterostructures have been obtained by Isothermal Vapor Growth Epitaxy in a reusable growth system which enables in situ doping during growth with foreign impurities. Ion milling was extensively used in preparation of the devices. Monolithic optical immersion has been applied for further improvement of performance. The 3D heterostructure devices exhibit performance exceeding that of conventional photodetectors. [reprint (PDF)]
14.	High operating temperature 320 x 256 middle-wavelength infrared focal plane array imaging based on an InAs/InGaAs/InAlAs/InP quantum dot infrared photodetector S. Tsao, H. Lim, W. Zhang, and M. Razeghi Virtual Journal of Nanoscale Science and Technology-- May 28, 2007 ...[Visit Journal][reprint (PDF)]
14.	InAs/InAs_1-xSb_x type-II superlattices for high performance long wavelength infrared detection M. Razeghi, A. Haddadi, A. M. Hoang, R. Chevallier, S. Adhikary, A. Dehzangi Proc. SPIE 9819, Infrared Technology and Applications XLII, 981909-- May 20, 2016 ...[Visit Journal] We report InAs/InAs1-xSbx type-II superlattice base photodetector as high performance long-wavelength infrared nBn device grown on GaSb substrate. The device has 6 μm-thick absorption region, and shows optical performance with a peak responsivity of 4.47 A/W at 7.9 μm, which is corresponding to the quantum efficiency of 54% at a bias voltage of negative 90 mV, where no anti-reflection coating was used for front-side illumination. At 77K, the photodetector’s 50% cut-off wavelength was ~10 μm. The device shows the detectivity of 2.8x10¹¹ cm•Hz^½/W at 77 K, where RxA and dark current density were 119 Ω•cm² and 4.4x10^-4 A/cm² , respectively, under -90 mV applied bias voltage [reprint (PDF)]
14.	Monolithic integrated photoreceiver for 1.3–1.55‐μm wavelengths: Association of a Schottky photodiode and a field‐effect transistor on GaInP‐GaInAs heteroepitaxy A. Hosseini Therani; D. Decoster; J. P. Vilcot; M. Razeghi J. Appl. Phys. 64, 2215–2218 (1988) -- March 24, 1988 ...[Visit Journal] We present a monolithic integrated circuit associating a Schottky photodiode and a field-effect transistor which has been fabricated, for the first time, on G8.0.49 InO.51 P /GaO,47 Ino.53 As strained heteroepitaxiaI material. Static, dynamic, and noise properties of the Schottky photodiode, the field-effect transistor, and the integrated circuit have been investigated and are reported. As an example, dynamic responsivity up to 50 A/W can be achieved at 1.3-pm wavelength for the integrated photoreceiver. The performance of the device is discussed, taking into account the integrated circuit design and the main characteristics of the material. [reprint (PDF)]
14.	Performance characteristics of high-purity mid-wave and long-wave infrared type-II InAs/GaSb superlattice infrared photodiodes A. Hood, M. Razeghi, V. Nathan and M.Z. Tidrow SPIE Conference, San Jose, CA, Vol. 6127, pp. 61270U-- January 23, 2006 ...[Visit Journal] The authors report on recent advances in the development of mid-, long-, and very long-wavelength infrared (MWIR, LWIR, and VLWIR) Type-II InAs/GaSb superlattice infrared photodiodes. The residual carrier background of binary Type-II InAs/GaSb superlattice photodiodes of cut-off wavelengths around 5 µm has been studied in the temperature range between 10 and 200 K. A four-point, capacitance-voltage technique on mid-wavelength and long-wavelength Type-II InAs/GaSb superlattice infrared photodiodes reveal residual background concentrations around 5×10¹⁴ cm^-3. Additionally, recent progress towards LWIR photodiodes for focal plane array imaging applications is presented. [reprint (PDF)]
14.	Very High Average Power at Room Temperature from λ ~ 5.9 μm Quantum Cascade Lasers J.S. Yu, S. Slivken, A. Evans, J. David and M. Razeghi Virtual Journal of Nanoscale Science & Technology 26-- May 26, 2003 ...[Visit Journal][reprint (PDF)]
14.	Quantum Sensing Using Type-II InAs/GaSb Superlattice for Infrared Detection M. Razeghi, A. Gin, Y. Wei, J. Bae, and J. Nah Microelectronics Journal, 34 (5-8)-- May 1, 2003 ...[Visit Journal] Large, regular arrays of bulk GaSb and InAs/GaSb Type-II superlattice pillars have been fabricated by electron beam lithography and dry etching. A 2.5 keV electron beam lithography system and metal evaporation are used to form the Au mask on superlattice and bulk substrates. Dry etching of these materials has been developed with BCl3:Ar, CH4:H2:Ar and cyclic CH₄:H₂:Ar/O₂ plasmas. Etch temperatures were varied from 20 to 150 °C. The diameter of the superlattice pillars was below 50 nm with regular 200 nm spacing. Bulk GaSb pillars were etched with diameters below 20 nm. Areas of dense nanopillars as large as 500 μm×500 μm were fabricated. The best height/diameter aspect ratio was approximately 10:1. To date, these are the smallest diameter III–V superlattice pillar structures reported, and the first nanopillars in the InAs/GaSb material system. The basic theory of these devices and surface passivation with SiO₂ and Si₃N₄ thin films has also been discussed. [reprint (PDF)]
14.	Crystallography of epitaxial growth of wurtzite-type thin films on sapphire substrates P. Kung, C.J. Sun, A. Saxler, H. Ohsato, and M. Razeghi Journal of Applied Physics 75 (9)-- May 1, 1994 ...[Visit Journal] In this article, we present a crystallographic model to describe the epitaxial growth of wurtzite‐type thin films such as gallium nitride (GaN) on different orientations of sapphire (Al2O3) substrates. Through this model, we demonstrate the thin films grown on (00⋅1)Al₂O₃ have a better epilayer‐substrate interface quality than those grown on (01⋅2)Al₂O₃. We also show the epilayer grown on (00⋅1)Al₂O₃ are gallium‐terminated, and both (00⋅1) and (01⋅2) surfaces of sapphire crystals are oxygen‐terminated. [reprint (PDF)]
14.	Amorphous ZnO films grown by room temperature pulsed laser deposition on paper and mylar for transparent electronics applications D.J. Rogers, V.E. Sandana, F. Hosseini Teherani, R. McClintock, M. Razeghi, and H.J. Drouhin SPIE Proceedings, San Francisco, CA (January 22-27, 2011), Vol. 7940, p. 79401K-- January 24, 2011 ...[Visit Journal] Recently, there has been a surge of activity in the development of next-generation transparent thin film transistors for use in applications such as electronic paper and flexible organic light emitting diode panels. Amongst the transparent conducting oxides attracting the most interest at present are Amorphous Oxide Semiconductors (AOS) based on ZnO because they exhibit enhanced electron mobility (μ), superior capacity for processability in air and improved thermodynamic stability compared with conventional covalent amorphous semiconductors and existing AOS. Moreover, they give excellent performance when fabricated at relatively low temperature and can readily be made in large area format. Thus, they are projected to resolve the trade-off between processing temperature and device performance and thereby allow fabrication on inexpensive heatsensitive substrates. For the moment, however, an undesireable post-deposition annealing step at a temperature of about 200ºC is necessary in order to obtain suitable electrical and optical properties. This paper demonstrates the possibility of directly engineering amorphous ZnO with relatively high conductiviy at room temperature on paper and mylar substrates using pulsed laser deposition. [reprint (PDF)]
14.	Dark current reduction in microjunction-based double electron barrier type-II InAs/InAsSb superlattice long-wavelength infrared photodetectors Romain Chevallier, Abbas Haddadi, & Manijeh Razeghi Scientific Reports 7, Article number: 12617-- October 3, 2017 ...[Visit Journal] Microjunction InAs/InAsSb type-II superlattice-based long-wavelength infrared photodetectors with reduced dark current density were demonstrated. A double electron barrier design was employed to reduce both bulk and surface dark currents. The photodetectors exhibited low surface leakage after passivation with SiO2, allowing the use of very small size features without degradation of the dark current. Fabricating microjunction photodetectors (25 × 25 µm² diodes with 10 × 10 µm² microjunctions) in combination with the double electron barrier design results in a dark current density of 6.3 × 10⁻⁶ A/cm² at 77 K. The device has an 8 µm cut-off wavelength at 77 K and exhibits a quantum efficiency of 31% for a 2 µm-thick absorption region, which results in a specific detectivity value of 1.2 × 10¹² cm·Hz^½/W. [reprint (PDF)]
14.	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)]
14.	MOCVD challenge for III-V semiconductor materials for photonic and electronic devices on alternative substrates M. Razeghi, M. Defour , F. Omnes, P. Maurel , E. Bigan , O. Acher, J. Nagle, F. Brillouet , J.C. Portal M. Razeghi, M. Defour, F. Omnes, P. Maurel, E. Bigan, O. Acher, J. Nagle, F. Brillouet, J.C. Portal, MOCVD challenge for III-V semiconductor materials for photonic and electronic devices on alternative substrates, Journal of Crystal Growth, Volume 93, Issues 1–4, 1988, Pages 776-781,-- January 1, 1988 ...[Visit Journal] High quality II[-V semiconductor heterojunctions, quantum wells and superlauices have been grown on lattice matched and alternative substrates such as silicon for photonic and electronic devices, using low pressure metalorganic chemical vapor deposition growth technique. [reprint (PDF)]
14.	Surface leakage current reduction in long wavelength infrared type-II InAs/GaSb superlattice photodiodes S. Bogdanov, B.M. Nguyen, A.M. Hoang, and M. Razeghi Applied Physics Letters, Vol. 98, No. 18, p. 183501-1-- May 2, 2011 ...[Visit Journal] Dielectric passivation of long wavelength infrared Type-II InAs/GaSb superlattice photodetectors with different active region doping profiles has been studied. SiO₂ passivation was shown to be efficient as long as it was not put in direct contact with the highly doped superlattice. A hybrid graded doping profile combined with the shallow etch technique reduced the surface leakage current in SiO₂ passivated devices by up to two orders of magnitude compared to the usual design. As a result, at 77 K the SiO(2) passivated devices with 10.5 μm cutoff wavelength exhibit an R₀A of 120 Ω·cm², R_maxA of 6000 Ω·cm², and a dark current level of 3.5×10⁻⁵ A·cm⁻² at −50 mV bias. [reprint (PDF)]
14.	Effects of substrate quality and orientation on the characteristics of III-nitride resonant tunneling diodes Z. Vashaei, C. Bayram, R. McClintock and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-27, 2011), Vol 7945, p. 79451A-- January 23, 2011 ...[Visit Journal] Al(Ga)N/GaN resonant tunneling diodes (RTDs) are grown by metal-organic chemical vapor deposition. The effects of material quality on room temperature negative differential resistance (NDR) behaviour of RTDs are investigated by growing the RTD structure on AlN, GaN, and lateral epitaxial overgrowth GaN templates. This reveals that NDR characteristics of RTDs are very sensitive to material quality (such as surface roughness and dislocations density). The effects of the aluminum content of AlGaN double barriers (DB) and polarization fields on NDR characteristic of AlGaN/GaN RTDs were also investigated by employing low dislocation density c-plane (polar) and m-plane (nonpolar) freestanding GaN substrates. Lower aluminum content in the DB RTD active layer and minimization of dislocations and polarization fields enabled a more reliable and reproducible NDR behaviour at room temperature. [reprint (PDF)]
14.	High power, electrically tunable quantum cascade lasers Steven Slivken; Manijeh Razeghi Proc. SPIE 9755, Quantum Sensing and Nano Electronics and Photonics-- February 13, 2016 ...[Visit Journal] Mid-infrared laser sources (3-14 μm wavelengths) which have wide spectral coverage and high output power are attractive for many applications. This spectral range contains unique absorption fingerprints of most molecules, including toxins, explosives, and nerve agents. Infrared spectroscopy can also be used to detect important biomarkers, which can be used for medical diagnostics by means of breath analysis. The challenge is to produce a broadband midinfrared source which is small, lightweight, robust, and inexpensive. We are currently investigating monolithic solutions using quantum cascade lasers. A wide gain bandwidth is not sufficient to make an ideal spectroscopy source. Single mode output with rapid tuning is desirable. For dynamic wavelength selection, our group is developing multi-section laser geometries with wide electrical tuning (hundreds of cm-1). These devices are roughly the same size as a traditional quantum cascade lasers, but tuning is accomplished without any external optical components. When combined with suitable amplifiers, these lasers are capable of multi-Watt single mode output powers. This manuscript will describe our current research efforts and the potential for high performance, broadband electrical tuning with the quantum cascade laser. [reprint (PDF)]

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