Center for Quantum Devices - Most Downloaded Journal Articles

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20.	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)]
20.	High power operation of λ ∼ 5.2–11 μm strain balanced quantum cascade lasers based on the same material composition N. Bandyopadhyay, Y. Bai, S. Slivken, and M. Razeghi Appl. Phys. Lett. 105, 071106 (2014)-- August 20, 2014 ...[Visit Journal] A technique based on composite quantum wells for design and growth of strain balanced Al_0.63In_0.37As/Ga_0.35In_0.65As/Ga_0.47In_0.53As quantum cascade lasers (QCLs) by molecular beam epitaxy (MBE), emitting in 5.2–11 μm wavelength range, is reported. The strained Al_0.63In_0.37As provides good electron confinement at all wavelengths, and strain balancing can be achieved through composite wells of Ga_0.35In_0.65As/Ga_0.47In_0.53As for different wavelength. The use of these fixed composition materials can avoid the need for frequent calibration of a MBE reactor to grow active regions with different strain levels for different wavelengths. Experimental results for QCLs emitting at 5.2, 6.7, 8.2, 9.1, and 11 μm exhibit good wall plug efficiencies and power across the whole wavelength range. It is shown that the emission wavelength can be predictably changed using the same design template. These lasers are also compatible with a heterogeneous broadband active region, consisting of multiple QCL cores, which can be produced in a single growth run. [reprint (PDF)]
20.	Al_xGa_1-xN Materials and Device Technology for Solar Blind Ultraviolet Photodetector Applications R. McClintock, P. Sandvik, K. Mi, F. Shahedipour, A. Yasan, C. Jelen, P. Kung, and M. Razeghi SPIE Conference, San Jose, CA, Vol. 4288, pp. 219-- January 22, 2001 ...[Visit Journal] There has been a growing interest for the development of solar blind ultraviolet (UV) photodetectors for use in a variety of applications, including early missile threat warning, flame monitoring, UV radiation monitoring and chemical/biological reagent detection. The Al_xGa_1-xN material system has emerged as the most promising approach for such devices. However, the control of the material quality and the device technology are still rather immature. We report here the metalorganic chemical vapor deposition, the n-type and the p-type doping of high quality Al_xGa_1-xN thin films on sapphire substrates over a wide range of Al concentration. [reprint (PDF)]
20.	The effect of doping the M-barrier in very long-wave type-II InAs/GaSb heterodiodes D. Hoffman, B.M. Nguyen, E.K. Huang, P.Y. Delaunay, M. Razeghi, M.Z. Tidrow and J. Pellegrino Applied Physics Letters, Vol. 93, No. 3, p. 031107-1-- July 21, 2008 ...[Visit Journal] A variation on the standard homo-diode Type-II superlattice with an M-barrier between the pi-region and the n-region is shown to suppress the dark currents. By determining the optimal doping level of the M-superlattice, dark current densities of 4.95 mA·cm^-2 and quantum efficiencies in excess of 20% have been demonstrated at the moderate reverse bias of 50 mV; allowing for near background-limited performance with a Johnson-noise detectivity of 3.11×10¹⁰ Jones at 77 K for a 14.58 µm cutoff wavelength for large area diodes without passivation. This is comparable to values for the state-of-the-art HgCdTe photodiodes. [reprint (PDF)]
20.	High power 1D and 2D photonic crystal distributed feedback quantum cascade lasers B. Gokden, Y. Bai, S. Tsao, N. Bandyopadhyay, S. Slivken and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-27, 2011), Vol. 7945, p. 79450C-- January 23, 2011 ...[Visit Journal] For many practical applications that need bright sources of mid-infrared radiation, single mode operation and good beam quality are also required. Quantum cascade lasers are prominent candidates as compact sources of mid-infrared radiation capable of delivering very high power both CW and under pulsed operation. While 1D photonic crystal distributed feedback structures can be used to get single mode operation from quantum cascade lasers with narrow ridge widths, novel 2D photonic crystal cavity designs can be used to improve spectral and spatial purity of broad area quantum cascade lasers. In this paper, we demonstrate high power, spatially and spectrally pure operation at room temperature from narrow ridge and broad area quantum cascade lasers with buried 1D and 2D photonic crystal structures. Single mode continuous wave emission at λ = 4.8 μm up to 700 mW in epi-up configuration at room temperature was observed from a 11 μm wide 5 mm long distributed feedback quantum cascade laser with buried 1D gratings. High peak powers up to 34 W was obtained from a 3mm long 400 μm wide 2D photonic crystal distributed feedback laser at room temperature under pulsed operation. The far field profile had a single peak normal to the laser facet and the M2 figure of merit was as low as 2.5. Emission spectrum had a dominating single mode at λ = 4.36 μm. [reprint (PDF)]
20.	Reliable High-Power Uncoated Al-free InGaAsP/GaAs Lasers for Cost-Sensitive Optical Communication and Processing Applications M. Razeghi SPIE Conference, Dallas, TX, -- November 4, 1997 ...[Visit Journal] Unlike InP-based systems for long-distance communication applications, GaAs-based optoelectronic systems mostly for local-area network, optical interconnection or optical computing are very cost-sensitive because often these optoelectronic devices constitute most of the cost for these applications and fewer users share the cost. Thus besides technical issues, the processing cost should be addressed in the selection of materials and fabrication methods. We discuss a number of major advantages of Al-free InGaAsP/GaAs lasers for these applications, such as not coating- requirement, low cost, high long-term reliability, high performance. We discuss recent preliminary results of Al- free lasers as a first step toward these optoelectronic applications. [reprint (PDF)]
20.	Fabrication of nanostructured heterojunction LEDs using self-forming Moth-Eye Arrays of n-ZnO Nanocones Grown on p-Si (111) by PLD D.J. Rogers; V.E. Sandana; F. Hosseini Teherani; M. Razeghi; H.-J. Drouhin Proc. SPIE 7217, Zinc Oxide Materials and Devices IV, 721708 (February 17, 2009)-- February 17, 2009 ...[Visit Journal] ZnO nanostructures were grown on Si (111) substrates using Pulsed Laser Deposition. The impact of growth temperature (T_s) and Ar pressure (P_Ar) on the morphology, crystal structure and photoluminescence was investigated. Various types of ZnO nanostructures were obtained. Self-forming arrays of vertically-aligned nanorods and nanocones with strong c-axis crystallographic orientation and good optical response were obtained at higher T_s. The nanocone, or "moth-eye" type structures were selected for LED development because of their graded effective refractive index, which could facilitate improved light extraction at the LED/air interface. Such moth-eye arrays were grown on p-type Si (111) substrates to form heteroj unction LEDs with the n-type ZnO nanocones acting as an active component of the device. These nanostructured LEDs gave rectifying I/V characteristics with a threshold voltage of about 6V and a blueish-white electroluminescence, which was clearly visible to the naked eye. [reprint (PDF)]
20.	8-13 μm InAsSb heterojunction photodiode operating at near room temperature J.D. Kim, S. Kim, D. Wu, J. Wojkowski, J. Xu, J. Piotrowski, E. Bigan, and M. Razeghi Applied Physics Letters 67 (18)-- October 30, 1995 ...[Visit Journal] p⁺-InSb/π-InAs_1−xSb_x/n⁺-InSb heterojunction photodiodes operating at near room temperature in the 8–13 μm region of infrared (IR) spectrum are reported. A room‐temperature photovoltaic response of up to 13 μm has been observed at 300 K with an x≊0.85 sample. The voltage responsivity‐area product of 3×10⁻⁵ V· cm²/W has been obtained at 300 K for the λ=10.6 μm optimized device. This was close to the theoretical limit set by the Auger mechanism, with a detectivity at room temperature of ≊1.5×10⁸ cm ·Hz^½/W. [reprint (PDF)]
20.	High Performance Solar-Blind Ultraviolet Focal Plane Arrays Based on AlGaN Erdem Cicek, Ryan McClintock, Abbas Haddadi, William A. Gaviria Rojas, and Manijeh Razeghi IEEE Journal of Quantum Electronics, Vol. 50, Issue 8, p 591-595-- August 1, 2014 ...[Visit Journal] We report on solar-blind ultraviolet, AlxGa1-x N- based,p-i-n,focal plane array (FPA) with 92% operability. At the peak detection wavelength of 278 nm, 320×256-FP A-pixel showed unbiased peak external quantum efficiency (EQE) and responsivity of 49% and 109 mA/W, respectively, increasing to 66% under 5 volts of reverse bias. Electrical measurements yielded a low-dark current density: <7×10^-9A/cm², at FPA operating voltage of 2 volts of reverse bias. [reprint (PDF)]
20.	InAsSbP/InAsSb/InAs Laser Diodes λ = 3.2 μm) Grown by Low-Pressure Metalorganic Chemical Vapor Deposition J. Diaz, G. Lukas, D. Wu, S. Kim, M. Erdtmann, E. Kaas, and M. Razeghi Applied Physics Letters 70 (1)-- January 6, 1997 ...[Visit Journal] We report metal–organic chemical-vapor deposition-grown double heterostructure InAsSbP/InAsSb/InAs diode lasers emitting at 3.2 μm operating at temperatures up to 220 K with threshold current density of 40 A/cm² at 77 K and characteristic temperature up to 42 K. Output powers as high as 260 mW in pulse mode and 60 mW in continuous wave operation have been obtained from an uncoated 100 μm stripe-width broad-area laser at 77 K. Comparison with theory shows that there is no significant nonradiative recombination mechanism for these lasers at 77 K. [reprint (PDF)]
20.	Two-dimensional magnetophonon resonance. I. GaInAs-InP superlattices J C Portal, J Cisowski, R J Nicholas, M A Brummell, M Razeghi and M A Poisson J C Portal et al 1983 J. Phys. C: Solid State Phys. 16 L573-- April 5, 1983 ...[Visit Journal] Magnetophonon resonance results are reported for two-dimensional electron gases confined in the GaInAs layers of GaInAs-InP superlattices. Two series of oscillations are observed: one due to scattering by the 'GaAs-like' LO phonon mode of GaInAs, and the second due to interaction with InP LO phonons. The strength of the latter series increases relative to the former as the GaInAs layer thickness is reduced. This is evidence for a long-range phonon interaction, with the InP phonon field extending into the GaInAs to couple significantly with the electrons bound in the quantum wells. No evidence of interface phonons is seen. [reprint (PDF)]
20.	Wafer-scale epitaxial lift-off of optoelectronic grade GaN from a GaN substrate using a sacrificial ZnO interlayer Akhil Rajan, David J Rogers, Cuong Ton-That, Liangchen Zhu, Matthew R Phillips, Suresh Sundaram, Simon Gautier, Tarik Moudakir, Youssef El-Gmili, Abdallah Ougazzaden, Vinod E Sandana, Ferechteh H Teherani, Philippe Bove, Kevin A Prior, Zakaria Djebbour, Ryan McClintock and Manijeh Razeghi Journal of Physics D: Applied Physics, Volume 49, Number 31 -- July 15, 2016 ...[Visit Journal] Full 2 inch GaN epilayers were lifted off GaN and c-sapphire substrates by preferential chemical dissolution of sacrificial ZnO underlayers. Modification of the standard epitaxial lift-off (ELO) process by supporting the wax host with a glass substrate proved key in enabling full wafer scale-up. Scanning electron microscopy and x-ray diffraction confirmed that intact epitaxial GaN had been transferred to the glass host. Depth-resolved cathodoluminescence (CL) analysis of the bottom surface of the lifted-off GaN layer revealed strong near-band-edge (3.33 eV) emission indicating a superior optical quality for the GaN which was lifted off the GaN substrate. This modified ELO approach demonstrates that previous theories proposing that wax host curling was necessary to keep the ELO etch channel open do not apply to the GaN/ZnO system. The unprecedented full wafer transfer of epitaxial GaN to an alternative support by ELO offers the perspective of accelerating industrial adoption of the expensive GaN substrate through cost-reducing recycling. [reprint (PDF)]
20.	Quantum Dot Infrared Photodetectors: Comparison Experiment and Theory H. Lim, W. Zhang, S. Tsao, T. Sills, J. Szafraniec, K. Mi, B. Movaghar, and M. Razeghi Physical Review B, 72-- August 17, 2005 ...[Visit Journal] We present data and calculations and examine the factors that determine the detectivities in self-assembled InAs and InGaAs based quantum dot infrared photodetectors (QDIPs). We investigate a class of devices that combine good wavelength selectivity with “high detectivity.” We study the factors that limit the temperature performance of quantum dot detectors. For this we develop a formalism to evaluate the optical absorption and the electron transport properties. We examine the performance limiting factors and compare theory with experimental data. We find that the notion of a phonon bottleneck does not apply to large-diameter lenslike quantum dots, which have many closely spaced energy levels. The observed strong decrease of responsivity with temperature is ultimately due to a rapid thermal cascade back into the ground states. High temperature performance is improved by engineering the excited state to be near the continuum. The good low temperature (77 K) performance in strongly bound QDIPs is shown to be due to the high gain and the low noise achievable in these micron size devices. [reprint (PDF)]
20.	Gas-Source Molecular Beam Epitaxy Growth of 8.5 μm Quantum Cascade Laser S. Slivken, C. Jelen, A. Rybaltowski, J. Diaz and M. Razeghi Applied Physics Letters 71 (18)-- November 1, 1997 ...[Visit Journal] We demonstrate preliminary results for an 8.5 μm laser emission from quantum cascade lasers grown in a single step by gas-source molecular beam epitaxy. 70 mW peak power per two facets is recorded for all devices tested at 79 K with 1 μs pulses at 200 Hz. For a 3 mm cavity length, lasing persists up to 270 K with a T0 of 180 K. [reprint (PDF)]
20.	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)]
20.	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)]
20.	On the interface properties of ZnO/Si electroluminescent diodes J.L. Pau, J. Piqueras, D.J. Rogers, F. Hosseini Teherani, K. Minder, R. McClintock, and M. Razeghi Journal of Applied Physics, Vol. 107, No. 3, p. 033719-1-- February 1, 2010 ...[Visit Journal] ZnO layers grown on n⁻–Si(100), n⁺–Si(100), and n^––Si(111) substrates by pulsed-laser deposition were found to give electroluminescence. Light emission was observed in the form of discrete spots for currents over 1 mA with a white appearance to the naked eye. The intensity of these spots showed an erratic behavior over time, appearing and disappearing at random, while showing an associated random telegraph noise in the current signal. Regardless the substrate used, the electroluminescence spectra had a main broadband emission centered at about 600 nm and a relatively small peak at around 380 nm which corresponds to the energy of ZnO near band edge emission. Furthermore, the devices exhibited rectifying characteristics, whose current blocking direction depended on the substrate orientation. Optimization of ZnO conductivity and performing sample growth in N₂ ambient were found to be critical to enhance the emission intensity. Rutherford backscattering characterization revealed the existence of an intermixed region at the interface between ZnO and Si. To study the electronic properties at the interface, frequency dependent capacitance measurements were carried out. The junction capacitance became frequency dependent at the bias voltages at which light emission occurs due to the relatively slow trapping and generation processes at deep centers. These centers are believed to play an important role in the mechanism of light emission. [reprint (PDF)]
20.	High-brightness LWIR quantum cascade lasers F. Wang, S. Slivken, and M. Razeghi F. Wang, S. Slivken, and M. Razeghi, High-brightness LWIR quantum cascade lasers, Optics Letters, vol. 46, No. 20, 5193 ...[Visit Journal] Long-wave infrared (LWIR, lambda~8-12 um) quantum cascade lasers (QCLs) are drawing increasing interest, as they provide the possibility of long-distance transmission of light through the atmosphere owing to the reduced water absorption. However, their development has been lagging behind the shorter wavelength QCLs due to much bigger technological challenges. In this Letter, through band structure engineering based on a highly localized diagonal laser transition strategy and out-coupler design using an electrically isolated taper structure, we demonstrate high beam quality single-mode LWIR QCLs with high-brightness (2.0 MW cm^-2 sr^-1 for lambda~10 um, 2.2 MW cm^-2 sr^-1 for lambda~9 um, 5.0 MW cm^-2 sr^-1 for lambda~8 um) light extraction from a single facet in continuous-wave operation at 15 ^oC. These results mark an important milestone in exploring the lighting capability of inter-sub-band semiconductor lasers in the LWIR spectral range. [reprint (PDF)]
20.	Growth of AlGaN on silicon substrates: a novel way to make back-illuminated ultraviolet photodetectors Ryan McClintock ; Manijeh Razeghi Proc. SPIE 9555, Optical Sensing, Imaging, and Photon Counting: Nanostructured Devices and Applications, 95550U-- August 28, 2015 ...[Visit Journal] AlGaN, with its tunable wide-bandgap is a good choice for the realization of ultraviolet photodetectors. AlGaN films tend to be grown on foreign substrates such as sapphire, which is the most common choice for back-illuminated devices. However, even ultraviolet opaque substrates like silicon holds promise because, silicon can be removed by chemical treatment to allow back-illumination,1 and it is a very low-cost substrate which is available in large diameters up to 300 mm. However, Implementation of silicon as the solar-blind PD substrates requires overcoming the lattice-mismatch (17%) with the AlxGa1-xN that leads to high density of dislocation and crack-initiating stress. In this talk, we report the growth of thick crack-free AlGaN films on (111) silicon substrates through the use of a substrate patterning and mask-less selective area regrowth. This technique is critical as it decouples the epilayers and the substrate and allows for crack-free growth; however, the masking also helps to reduce the dislocation density by inclining the growth direction and encouraging dislocations to annihilate. A back-illuminated p-i-n PD structure is subsequently grown on this high quality template layer. After processing and hybridizing the device we use a chemical process to selectively remove the silicon substrate. This removal has minimal effect on the device, but it removes the UV-opaque silicon and allows back-illumination of the photodetector. We report our latest results of back-illuminated solar-blind photodetectors growth on silicon. [reprint (PDF)]
20.	Antimonite-based gap-engineered type-II superlattice materials grown by MBE and MOCVD for the third generation of infrared imagers Manijeh Razeghi, Arash Dehzangi, Donghai Wu, Ryan McClintock, Yiyun Zhang, Quentin Durlin, Jiakai Li, Fanfei Meng Proc. SPIE Defense + Commercial Sensing,Infrared Technology and Applications XLV, 110020G -- May 7, 2019 ...[Visit Journal] Third generation of infrared imagers demand performances for higher detectivity, higher operating temperature, higher resolution, and multi-color detection all accomplished with better yield and lower manufacturing costs. Antimonidebased gap-engineered Type-II superlattices (T2SLs) material system is considered as a potential alternative for MercuryCadmium-Telluride (HgCdTe) technology in all different infrared detection regimes from short to very long wavelengths for the third generation of infrared imagers. This is due to the incredible growth in the understanding of its material properties and improvement of device processing which leads to design and fabrication of better devices. We will present the most recent research results on Antimonide-based gap-engineered Type-II superlattices, such as highperformance dual-band SWIR/MWIR photo-detectors and focal plane arrays for different infrared regimes, toward the third generation of infrared imaging systems at the Center for Zuantum Devices. Comparing metal-organic chemical vapor deposition (MOCVD), vs molecular beam epitaxy (MBE). [reprint (PDF)]
20.	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)]
20.	Al_xGa_1-xN p-i-n Photodiodes on Sapphire Substrates D. Walker, P. Kung, P. Sandvik, J. Wu, M. Hamilton, I.H. Lee, J. Diaz, and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 ...[Visit Journal] We report the fabrication and characterization of Al_xGa1-xN p-i-n photodiodes (0.05 ≤ to X ≤ 0.30) grown on sapphire by low-pressure metalorganic chemical vapor deposition. The devices present a visible-rejection of about four orders of magnitude with a cutoff wavelength that shifts from 350 nm to 291 nm. They also exhibit a constant responsivity for five decades (30 mW/m² to 1 kW/m²) of optical power density. Using capacitance measurements, the values for the acceptor concentration in the p-Al_xGa_1-xN region and the unintentional donor concentration in the intrinsic region are found. Photocurrent decays are exponential for high load resistances, with a time constant that corresponds to the RC product of the system. For low load resistances the transient response becomes non-exponential, with a decay time longer than the RC constant. [reprint (PDF)]
20.	AlGaN-based deep-ultraviolet 320 x 256 focal plane array E. Cicek, Z. Vashaei, E.K. Huang, R. McClintock and M. Razeghi OSA Optics Letters, Vol. 37, No. 5, p. 896-898-- March 1, 2012 ...[Visit Journal] We report the synthesis, fabrication, and testing of a 320 × 256 focal plane array (FPA) of back-illuminated, solarblind, p-i-n, Al_xGa_1−xN–based detectors, fully realized within our research laboratory. We implemented a pulse atomic layer deposition technique for the metalorganic chemical vapor deposition growth of thick, high-quality, crack-free, high Al composition Al_xGa_1−xN layers. The FPA is hybridized to a matching ISC 9809 readout integrated circuit and operated in a SE-IR camera system. Solar-blind operation is observed throughout the array with peak detection occurring at wavelengths of 256 nm and lower, and falling off three orders of magnitude by ∼285 nm. By developing an opaque masking technology, the visible response of the ROIC is significantly reduced; thus the need for external filtering to achieve solar- and visible-blind operation is eliminated. This allows the FPA to achieve high external quantum efficiency (EQE); at 254 nm, average pixels showed unbiased peak responsivity of 75 mA∕W, which corresponds to an EQE of ∼37%. Finally, the uniformity of the FPA and imaging properties are investigated. [reprint (PDF)]
20.	Fabrication and characterization of novel hybrid green light emitting didoes based on substituting n-type ZnO for n-type GaN in an inverted p-n junction C. Bayram, D. Rogers, F. H. Teherani, and M. Razeghi Journal of Vacuum Science and Technology B, Vol. 27, No. 3, May/June, p. 1784-1788-- May 29, 2009 ...[Visit Journal] Details of the fabrication and characterization of hybrid green light emitting diodes, composed of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN on AlN/sapphire, are reported. Scanning electron microscope, atomic force microscopy, high resolution x-ray diffraction, and photoluminescence were used to study the hybrid device. The effects of solvents, annealing, and etching on n-ZnO are discussed. Successful hybridization of ZnO and (In)GaN into a green light emitting diode was realized. [reprint (PDF)]
20.	Lateral epitaxial overgrowth of GaN films on sapphire and silicon substrates P. Kung, D. Walker, M. Hamilton, J. Diaz, and M. Razeghi Applied Physics Letters 74 (4)-- January 25, 1999 ...[Visit Journal] We report the lateral epitaxial overgrowth of GaN films on (00.1) Al₂O₃ and (111) Si substrates by metalorganic chemical vapor deposition. The lateral epitaxial overgrowth 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 lateral epitaxial overgrown films. Lateral growth rates more than five times as high as vertical growth rates were achieved for both lateral epitaxial overgrowths of GaN on sapphire and silicon substrates. [reprint (PDF)]

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