Center for Quantum Devices - Most Downloaded Journal Articles

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11.	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)]
11.	GaInAsP/InP 1.35 μm Double Heterostructure Laser Grown on Silicon Substrate by Metalorganic Chemical Vapor Deposition K. Mobarhan, C. Jelen, E. Kolev, and M. Razeghi Journal of Applied Physics 74 (1)-- July 1, 1993 ...[Visit Journal] A 1.35 μm GaInAsP/InP double heterostructure laser has been grown on a Si substrate using low‐pressure metalorganic chemical vapor deposition. This was done without the use of a superlattice layer or a very thick InP buffer layer, which are used to prevent the dislocations from spreading into the active layer. Pulsed operation with output power of over 200 mW per facet was achieved at room temperature for broad area lasers with 20 μm width and 170 μm cavity length. The threshold current density of a 350 μm cavity length device was 9.8 kA/cm². The characteristic temperature was 66 K. [reprint (PDF)]
11.	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)]
11.	*High quality AlN and GaN epilayers grown on (001) sapphire, (100) and (111) silicon substrates P. Kung, A. Saxler, X. Zhang, D. Walker, T.C. Wang, I. Ferguson, and M. Razeghi Applied Physics Letters 66 (22)-- May 29, 1995** ...[Visit Journal] The growth of high quality AlN and GaN thin films on basal plane sapphire, (100), and (111) silicon substrates is reported using low pressure metalorganic chemical vapor deposition. X-ray rocking curve linewidths of about 100 and 30 arcsec were obtained for AlN and GaN on sapphire, respectively. Room‐temperature optical transmission and photoluminescence (of GaN) measurements confirmed the high quality of the films. The luminescence at 300 and 77 K of the GaN films grown on basal plane sapphire, (100), and (111) silicon was compared. [reprint (PDF)]
11.	Optical losses of Al-free lasers for λ = 0.808 and 0.98 μm H. Yi, J. Diaz, B. Lane, and M. Razeghi Applied Physics Letters 69 (20)-- November 11, 1996 ...[Visit Journal] In this work, we study the origin of the optical losses in Al‐free InGaAsP/GaAs (λ=0.808 μm) and InGaAs/GaAs/InGaP (λ=0.980 μm) lasers. Theoretical modeling and the experimental results indicate that the scattering of the laser beam by refractive index fluctuation in the alloys is the dominant loss in our lasers, and the loss due to the free‐carrier absorption and scattering by interface roughness are negligible. [reprint (PDF)]
11.	Toward realizing high power semiconductor terahertz laser sources at room temperature Manijeh Razeghi Proc. SPIE 8023, Terahertz Physics, Devices, and Systems V: Advance Applications in Industry and Defense, 802302 (May 25, 2011)-- May 25, 2011 ...[Visit Journal] The terahertz (THz) spectral range offers promising applications in science, industry, and military. THz penetration through nonconductors (fabrics, wood, plastic) enables a more efficient way of performing security checks (for example at airports), as illegal drugs and explosives could be detected. Being a non-ionizing radiation, THz radiation is environment-friendly enabling a safer analysis environment than conventional X-ray based techniques. However, the lack of a compact room temperature THz laser source greatly hinders mass deployment of THz systems in security check points and medical centers. In the past decade, tremendous development has been made in GaAs/AlGaAs based THz Quantum Cascade Laser (QCLs), with maximum operating temperatures close to 200 K (without magnetic field). However, higher temperature operation is severely limited by a small LO-phonon energy (∼ 36 meV) in this material system. With a much larger LO-phonon energy of ∼ 90 meV, III-Nitrides are promising candidates for room temperature THz lasers. However, realizing high quality material for GaN-based intersubband devices presents a significant challenge. Advances with this approach will be presented. Alternatively, recent demonstration of InP based mid-infrared QCLs with extremely high peak power of 120 W at room temperature opens up the possibility of producing high power THz emission with difference frequency generation through two mid-infrared wavelengths. [reprint (PDF)]
11.	Thermal conductivity tensors of the cladding and active layers of antimonide infrared lasers and detectors Chuanle Zhou, I. Vurgaftman, C. L. Canedy, C. S. Kim, M. Kim, W. W. Bewley, C. D. Merritt, J. Abell, J. R. Meyer, A. Hoang, A. Haddadi, M. Razeghi, and M. Grayson Optical Materials Express. 2013;3(10):1632-1640.-- October 1, 2013 ...[Visit Journal] The in-plane and cross-plane thermal conductivities of the cladding layers and active quantum wells of interband cascade lasers and type-II superlattice infrared detector are measured by the 2-wire 3ω method. The layers investigated include InAs/AlSb superlattice cladding layers, InAs/GaInSb/InAs/AlSb W-active quantum wells, an InAs/GaSb superlattice absorber, an InAs/GaSb/AlSb M-structure, and an AlAsSb digital alloy. The in-plane thermal conductivity of the InAs/AlSb superlattice is 4-5 times higher than the cross-plane value. The isotropic thermal conductivity of the AlAsSb digital alloy matches a theoretical expectation, but it is one order of magnitude lower than the only previously-reported experimental value. [reprint (PDF)]
11.	On the performance and surface passivation of type-II InAs/GaSb superlattice photodiodes for the very-long- wavelength infrared A. Hood, M. Razeghi, E. Aifer, G.J. Brown Applied Physics Letters 87 (1)-- October 10, 2005 ...[Visit Journal] We demonstrate very-long-wavelength infrared Type-II InAs/GaSb superlattice photodiodes with a cutoff wavelength (λ_c,50%) of 17 μm. We observed a zero-bias, peak Johnson noise-limited detectivity of 7.63×10⁹ cm·Hz^½/W at 77 K with a 90%-10% cutoff width of 17 meV, and quantum efficiency of 30%. Variable area diode zero-bias resistance-area product (R₀A) measurements indicated that silicon dioxide passivation increased surface resistivity by nearly a factor of 5, over unpassivated photodiodes, and increased overall R₀A uniformity. The bulk R₀A at 77 K was found to be 0.08 Ω·cm², with RA increasing more than twofold at 25 mV reverse bias. [reprint (PDF)]
11.	Reliability of strain-balanced Ga_0.331In_0.669As/Al_0.659In_0.341As/InP quantum-cascade lasers under continuous-wave room-temperature operation A. Evans and M. Razeghi Applied Physics Letters, 88 (26)-- June 26, 2006 ...[Visit Journal] Constant current aging is reported for two randomly selected high-reflectivity-coated QCLs with an output power over 100 mW. QCLs are tested under continuous-wave operation at a heat sink temperature of 298 K(25 °C) corresponding to an internal temperature of 378 K (105 °C). Over 4000 h of continuous testing is reported without any decrease in output power. [reprint (PDF)]
10.	p-Type thin film field effect transistors based on lithium-doped nickel oxide channels grown by pulsed laser deposition V. E. Sandana; D. J. Rogers; F. H. Teherani; P. Bove; R. McClintock; M. Razeghi SPIE Proceedings Volume 10919, Oxide-based Materials and Devices X; 109191H -- March 12, 2019 ...[Visit Journal] Staggered back-gated Field Effect Transistor (FET) structures were made by growing Li-doped NiO on Si₃N₄/SiO₂/Si (111) using room temperature pulsed laser deposition. Optical studies showed over 80% transmission for the NiO:Li channel at wavelengths > 500nm. The MISFET revealed rectifying transfer characteristics, with a V_ON close to zero, a channel mobility of ~ 1 cm²/V·s, a gate leakage current (at +5V) of 0.8 mA and an ION/IOFF ratio (at a Vgs of −15V) of ~ 10³. The transistors showed enhancement-mode output characteristics indicative of a p-type channel with sharp pinchoff, hard saturation, a comparatively high (milliampere range) Id and a relatively low on-resistance of ~11 kΩ. Hence the adoption of Li doping in NiO channels would appear to be a promising approach to obtain p-type TFTs with superior transparency, speed and energy efficiency. [reprint (PDF)]
10.	Radiometric characterization of long-wavelength infrared type II strained layer superlattice focal plane array under low-photon irradiance conditions J. Hubbs, V. Nathan, M. Tidrow, and M. Razeghi Optical Engineering, Vol. 51, No. 6, p. 064002-1-- June 15, 2012 ...[Visit Journal] We present the results of the radiometric characterization of an “M” structure long wavelength infrared Type-II strained layer superlattice(SLS) infrared focal plane array (IRFPA) developed by Northwestern University (NWU). The performance of the M-structure SLS IRFPA was radiometrically characterized as a function of photon irradiance, integration time, operating temperature, and detector bias. Its performance is described using standard figures of merit: responsivity, noise, and noise equivalent irradiance. Assuming background limited performance operation at higher irradiances, the detector quantum efficiency for the SLS detector array is approximately 57%. The detector dark density at 80 K is 142 μA∕cm², which represents a factor of seven reduction from previously measured devices. [reprint (PDF)]
10.	The new oxide paradigm for solid state ultraviolet photodetectors D. J. Rogers, P. Bove, X. Arrateig, V. E. Sandana, F. H. Teherani, M. Razeghi, R. McClintock, E. Frisch, S. Harel, Proceedings Volume 10533, Oxide-based Materials and Devices IX; 105331P-- March 22, 2018 ...[Visit Journal] The bandgap of wurzite ZnO layers grown on 2 inch diameter c-Al₂O₃ substrates by pulsed laser deposition was engineered from 3.7 to 4.8 eV by alloying with Mg. Above this Mg content the layers transformed from single phase hcp to mixed hcp/fcc phase before becoming single phase fcc above a bandgap of about 5.5 eV. Metal-Semiconductor-Metal (MSM) photodetectors based on gold Inter-Digitated-Transducer structures were fabricated from the single phase hcp layers by single step negative photolithography and then packaged in TO5 cans. The devices gave over 6 orders of magnitude of separation between dark and light signal with solar rejection ratios (I270 : I350) of over 3 x 10⁵ and dark signals of 300 pA (at a bias of −5V). Spectral responsivities were engineered to fit the “Deutscher Verein des Gas- und Wasserfaches” industry standard form and gave over two decade higher responsivities (14 A/W, peaked at 270 nm) than commercial SiC based devices. Homogeneous Ga₂O₃ layers were also grown on 2 inch diameter c-Al₂O₃ substrates by PLD. Optical transmission spectra were coherent with a bandgap that increased from 4.9 to 5.4 eV when film thickness was decreased from 825 to 145 nm. X-ray diffraction revealed that the films were of the β-Ga₂O₃ (monoclinic) polytype with strong (−201) orientation. β-Ga₂O₃ MSM photodetectors gave over 4 orders of magnitude of separation between dark and light signal (at −5V bias) with dark currents of 250 pA and spectral responsivities of up to 40 A/W (at -0.75V bias). It was found that the spectral responsivity peak position could be decreased from 250 to 230 nm by reducing film thickness from 825 to 145 nm. This shift in peak responsivity wavelength with film thickness (a) was coherent with the apparent bandgap shift that was observed in transmission spectroscopy for the same layers and (b) conveniently provides a coverage of the spectral region in which MgZnO layers show fcc/hcp phase mixing. [reprint (PDF)]
10.	Suppressing Spectral Crosstalk in Dual-Band LongWavelength Infrared Photodetectors With Monolithically Integrated Air-Gapped Distributed Bragg Reﬂectors Yiyun Zhang, Abbas Haddadi, Arash Dehzangi , Romain Chevallier, Manijeh Razeghi IEEE Journal of Quantum Electronics Volume: 55, Issue:1-- November 22, 2018 ...[Visit Journal] Antimonide-based type-II superlattices (T2SLs) have made possible the development of high-performance infrared cameras for use in a wide variety of thermal imaging applications, many of which could beneﬁt from dual-band imaging. The performance of this material system has not reached its limits. One of the key issues in dual-band infrared photodetection is spectral crosstalk. In this paper, air-gapped distributed Bragg reﬂectors (DBRs) have been monolithically integrated between the two channels in long-/very long-wavelength dualband InAs/InAs_1−xSb_x/AlAs_1−xSb_x-based T2SLs photodetectors to suppress the spectral crosstalk. This air-gapped DBR has achieved a signiﬁcant spectral suppression in the 4.5–7.5-µm photonic stopband while transmitting the optical wavelengths beyond 7.5 µm, which is conﬁrmed by theoretical calculations, numerical simulation, and experimental results. [reprint (PDF)]
10.	Gain and recombination dynamics of quantum-dot infrared photodetecto H. Lim, B. Movaghar, S. Tsao, M. Taguchi, W. Zhang, A.A. Quivy, and M. Razeghi Virtual Journal of Nanoscale Science & Technology-- December 4, 2006 ...[Visit Journal][reprint (PDF)]
10.	Quantum-dot infrared photodetectors and focal plane arrays M. Razeghi, H. Lim, S. Tsao, M. Taguchi, W. Zhang, and A.A. Quivy SPIE Infrared Technology and Applications Conference, April 17-21, 2006, Orlando, FL Proceedings – Infrared Technology and Applications XXXII, Vol. 6206, p. 62060I-1-- April 21, 2006 ...[Visit Journal] We report our recent results about mid-wavelength infrared quantum-dot infrared photodetectors (QDIPs) grown by low-pressure metalorganic chemical vapor deposition. A very high responsivity and a very low dark current were obtained. A high peak detectivity of the order of 3×10¹² Jones was achieved at 77 K. The temperature dependent device performance was also investigated. The improved temperature insensitivity compared to QWIPs was attributed to the properties of quantum dots. The device showed a background limited performance temperature of 220 K with a 45° field of view and 300K background. [reprint (PDF)]
10.	Study on the effects of minority carrier leakage in InAsSb/InPAsSb double heterostructure B. Lane, D. Wu, H.J. Yi, J. Diaz, A. Rybaltowski, S. Kim, M. Erdtmann, H. Jeon and M. Razeghi Applied Physics Letters 70 (11)-- April 17, 1997 ...[Visit Journal] InAs_xSb_1−x/InP_1−x−yAs_xSb_y double heterostructures have been grown on InAs substrates by metal-organic chemical vapor deposition. The minority carrier leakage to the cladding layers was studied with photoluminescence measurements on the InAsSb/InPAsSb double heterostructures. A carrier leakage model is used to extract parameters related to the leakage current (diffusion-coefficient and length) from experimental results. Using the obtained parameters, the temperature dependence of the threshold current density of InAsSb/InPAsSb double heterostructure lasers is predicted and compared with experimental results. [reprint (PDF)]
10.	High quality LEO growth and characterization of GaN films on Al₂O₃ and Si substrates M. Razeghi, P. Kung, D. Walker, M. Hamilton, and J. Diaz SPIE International Conference on Solid State Crystals, Zakopane, Poland; Proceedings 3725-- October 12, 1998 ...[Visit Journal] We report the lateral epitaxial overgrowth (LEO) of GaN films on (00.1) Al₂O₃ and (111) Si substrates by metalorganic chemical vapor deposition. The LEO on Si substrates was possible after achieving quasi monocrystalline GaN template films on (111) Si substrates. X-ray diffraction, photoluminescence, scanning electron microscopy and atomic force microscopy were used to assess the quality of the LEO films. Lateral growth rates more than 5 times as high as vertical growth rates were achieved for both LEO growths of GaN on sapphire and silicon substrates. [reprint (PDF)]
10.	AlN/GaN double-barrier resonant tunneling diodes grown by metal-organic chemical vapor deposition C. Bayram, Z. Vashaei and M. Razeghi Applied Physics Letters, Vol. 96, No. 4, p. 042103-1-- January 25, 2010 ...[Visit Journal] AlN/GaN double-barrier resonant tunneling diodes (RTDs) were grown by metal-organic chemical vapor deposition on sapphire. RTDs were fabricated via standard processing steps. RTDs demonstrate a clear negative differential resistance (NDR) at room temperature (RT). The NDR was observed around 4.7 V with a peak current density of 59 kA/cm² and a peak-to-valley ratio of 1.6 at RT. Dislocation-free material is shown to be the key for the performance of GaN RTDs. [reprint (PDF)]
10.	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)]
10.	Passivation of Type-II InAs/GaSb superlattice photodetectors A. Hood, Y. Wei, A. Gin, M. Razeghi, M. Tidrow, and V. Nathan SPIE Conference, Jose, CA, Vol. 5732, pp. 316-- January 22, 2005 ...[Visit Journal] Leakage currents limit the operation of high performance Type-II InAs/GaSb superlattice photodiode technology. Surface leakage current becomes a dominant limiting factor, especially at the scale of a focal plane array pixel (< 25 µm) and must be addressed. A reduction of the surface state density, unpinning the Fermi level at the surface, and appropriate termination of the semiconductor crystal are all aims of effective passivation. Recent work in the passivation of Type-II InAs\GaSb superlattice photodetectors with aqueous sulfur-based solutions has resulted in increased R₀A products and reduced dark current densities by reducing the surface trap density. Additionally, photoluminescence of similarly passivated Type-II InAs/GaSb superlattice and InAs GaSb bulk material will be discussed. [reprint (PDF)]
10.	Concentration gradient at an InP/GaAs interface determined by Auger analysis on a chemical bevel J. Cazaux; P. Etienne; M. Razeghi J. Cazaux, P. Etienne, M. Razeghi; Concentration gradient at an InP/GaAs interface determined by Auger analysis on a chemical bevel. J. Appl. Phys. 15 May 1986; 59 (10): 3598–3601-- June 15, 1986 ...[Visit Journal] Experimental results of Auger profiles obtained on a chemical bevel of an InP/GaAs structure are reported. A theoretical procedure is established to convert the intensity profile into concentration profiles. It is applied to evaluate the concentration distribution of each species–Ga, In, As, P–independently of each others with a precision of ±5%. It is verified that the composition of the interface is GaxIn1−xAsyP1−y (0≤x, y≤1). Owing to differences between the atomic diffusions of III‐ and V‐type elements, the transition region can be subdivided into three regions having the following compositions: (i) GaAsyP1−y with 0.87≤y≤1; (ii) GaxIn1−xAsyP1−y with 0≤y≤0.87 and 0.24≤x<1; (iii) PGaxIn1−x with x<0.24. The width of each region is also indicated. [reprint (PDF)]
10.	Exciton localization in group-III nitride quantum wells V.I. Litvinov and M. Razeghi Physical Review B 59 (15)-- May 15, 1999 ...[Visit Journal] Exciton density of states broadened by compositional disorder in the group-III nitride quantum well is calculated. The excitonic photoluminescence linewidth is estimated and related to the material parameters of the alloy for two limiting cases of two-dimensional (2D) and three-dimensional excitons in the quantum well. It is shown that the effect of the compositional fluctuations depends on dimensionality of the exciton: the 2D excitons are more sensitive to the inhomogeneities than 3D ones. The broad near-band-gap energy states distribution for quasi-two-dimensional excitons is consistent with the experimental evidence of the spontaneous and stimulated emissions from excitonic states localized on compositional fluctuations. [reprint (PDF)]
10.	Geiger-mode operation of back-illuminated GaN avalanche photodiodes J. L. Pau, R. McClintock, K. Minder, C. Bayram, P. Kung, M. Razeghi, E. Muñoz, and D. Silversmith Applied Physics Letters, Vol. 91, No. 04, p. 041104 -1-- July 23, 2007 ...[Visit Journal] We report the Geiger-mode operation of back-illuminated GaN avalanche photodiodes fabricated on transparent AlN templates specifically for back illumination in order to enhance hole-initiated multiplication. The spectral response in Geiger-mode operation was analyzed under low photon fluxes. Single photon detection capabilities were demonstrated in devices with areas ranging from 225 to 14,063 µm². Single photon detection efficiency of 20% and dark count rate < 10 kHz were achieved in the smallest devices. [reprint (PDF)]
10.	Thin film transistors with wurtzite ZnO channels grown on Si₃N₄/SiO₂/Si (111) substrates by pulsed laser deposition D.J. Rogers; V.E. Sandana; F. Hosseini Teherani; M. Razeghi Proc. SPIE 7603, Oxide-based Materials and Devices, 760318 (March 02, 2010)-- March 7, 2010 ...[Visit Journal] Thin Film Transistors (TFT) were made by growing ZnO on Si₃N₄/SiO₂/Si (111) substrates by pulsed laser deposition. X-ray diffraction and scanning electron microscope studies revealed the ZnO to have a polycrystalline wurtzite structure with a smooth surface, good crystallographic quality and a strong preferential c-axis orientation. Transmission studies in similar ZnO layers on glass substrates showed high transmission over the whole visible spectrum. Electrical measurements of a back gate geometry FET showed an enhancement-mode response with hard saturation, mA range Id and a V_ON ∼ 0V. When scaled down, such TFTs may be of interest for high frequency applications. [reprint (PDF)]
10.	GaN nanostructured p-i-n photodiodes J.L. Pau, C. Bayram, P. Giedraitis, R. McClintock, and M. Razeghi Applied Physics Letters, Vol. 93, No. 22, p. 221104-1-- December 1, 2008 ...[Visit Journal] We report the fabrication of nanostructured p-i-n photodiodes based on GaN. Each device comprises arrays of ~200 nm diameter and 520 nm tall nanopillars on a 1 µm period, fabricated by e-beam lithography. Strong rectifying behavior was obtained with an average reverse current per nanopillar of 5 fA at −5 V. In contrast to conventional GaN diodes, nanostructured devices reproducibly show ideality factors lower than 2. Enhanced tunneling through sidewall surface states is proposed as the responsible mechanism for this behavior. Under backillumination, the quantum efficiency in nanostructured devices is partly limited by the collection efficiency of holes into the nanopillars. [reprint (PDF)]

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