Center for Quantum Devices - Most Downloaded Journal Articles

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15.	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)]
15.	Room‐temperature excitons in Ga0.47In0.53As‐InP superlattices grown by low‐pressure metalorganic chemical vapor deposition M. Razeghi; J. Nagle; P. Maurel; F. Omnes; J. P. Pocholle Appl. Phys. Lett. 49, 1110–1111 (1986)-- October 27, 1986 ...[Visit Journal] Very high quality Gao.47 InO. 53 As-InP heterojunctions, quantum wells, and superlattices have been grown by low-pressure metalorganic chemical vapor deposition. Excitation spectroscopy shows evidence of strong and wen-resolved exciton peaks in the luminescence and excitation spectra of GalnAs-lnP quantum wells. Optical absorption spectra show room-temperature excitons in GalnAs· InP superlattices. [reprint (PDF)]
15.	Chemical lift-off and direct wafer bonding of GaN/InGaN P-I-N structures grown on ZnO K. Pantzas, D.J. Rogers, P. Bove, V.E. Sandana, F.H. Teherani, Y. El Gmili, M. Molinari, G. Patriarche, L. Largeau, O. Mauguin, S. Suresh, P.L. Voss, M. Razeghi, A. Ougazzaden Journal of Crystal Growth, Volume 435, Pages 105-109-- November 7, 2015 ...[Visit Journal] p-GaN/i-InGaN/n-GaN (PIN) structures were grown epitaxially on ZnO-buffered c-sapphire substrates by metal organic vapor phase epitaxy using the industry standard ammonia precursor for nitrogen. Scanning electron microscopy revealed continuous layers with a smooth interface between GaN and ZnO and no evidence of ZnO back-etching. Energy Dispersive X-ray Spectroscopy revealed a peak indium content of just under 5at% in the active layers. The PIN structure was lifted off the sapphire by selectively etching away the ZnO buffer in an acid and then direct bonded onto a glass substrate. Detailed high resolution transmission electron microscopy and grazing incidence X-ray diffraction studies revealed that the structural quality of the PIN structures was preserved during the transfer process. [reprint (PDF)]
15.	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)]
15.	Direct growth of thick AlN layers on nanopatterned Si substrates by cantilever epitaxy Ilkay Demir, Yoann Robin, Ryan McClintock, Sezai Elagoz, Konstantinos Zekentes, and Manijeh Razeghi Phys. Status Solidi A, pp. 1–6-- September 30, 2016 ...[Visit Journal] AlN layers have been grown on 200 nm period of nanopatterned Si (111) substrates by cantilever epitaxy and compared with AlN layers grown by maskless lateral epitaxial overgrowth (LEO) on micropatterned Si (111) substrates. The material quality of 5–10 µm thick AlN grown by LEO is comparable to that of much thinner layers (2 µm) grown by cantilever epitaxy on the nanopatterned substrates. Indeed, the latter exhibited root mean square (RMS) roughness of 0.65 nm and X-ray diffraction full width at half-maximum (FWHM) of 710 arcsec along the (0002) reflection and 930 arcsec along the (10̅15) reflection. The corresponding room temperature photoluminescence spectra was dominated by a sharp band edge peak. Back emission ultra violet light emitting diodes (UV LEDs) were fabricated by flip chip bonding to patterned AlN heat sinks followed by complete Si (111) substrate removal demonstrating a peak pulsed power of ∼0.7 mW at 344 nm peak emission wavelength. The demonstrated UV LEDs were fabricated on a cost effective epitaxial structure grown on the nanopatterned Si substrate with a total thickness of 3.3 µm [reprint (PDF)]
15.	Room temperature operation of 8-12 μm InSbBi infrared photodetectors on GaAs substrates J.J. Lee, J.D. Kim, and M. Razeghi Applied Physics Letters 73 (5)-- August 3, 1998 ...[Visit Journal] We report the room temperature operation of 8–12 μm InSbBi long-wavelength infrared photodetectors. The InSbBi/InSb heterostructures were grown on semi-insulating GaAs (001) substrates by low pressure metalorganic chemical vapor deposition. The voltage responsivity at 10.6 μm was about 1.9 mV/W at room temperature and the corresponding Johnson noise limited detectivity was estimated to be about 1.2×10⁶ cm·Hz^½/W. The carrier lifetime derived from the voltage dependent responsivity measurements was about 0.7 ns. [reprint (PDF)]
15.	Positive and negative luminescence in binary Type-II InAs/GaSb superlattice photodiodes D. Hoffman and M. Razeghi SPIE Conference, San Jose, CA, Vol. 6127, pp. 61271H-- January 23, 2006 ...[Visit Journal] In the present work, we show measurements of both positive and negative luminescence of binary Type-II InAs/GaSb superlattice photodiodes in the 3 to 13 μm spectral range. Through a radiometric calibration technique, we demonstrate temperature independent negative luminescence efficiencies of 45 % in the midwavelength (MWIR) sample from 220 K to 320 K without anti-reflective coating and values reaching 35 % in the long wavelength infrared (LWIR) spectrum sample. [reprint (PDF)]
15.	Electrically pumped photonic crystal distributed feedback quantum cascade lasers Y. Bai, P. Sung, S.R. Darvish, W. Zhang, A. Evans, S. Slivken, and M. Razeghi SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 69000A-1-8.-- February 1, 2008 ...[Visit Journal] We demonstrate electrically pumped, room temperature, single mode operation of photonic crystal distributed feedback (PCDFB) quantum cascade lasers emitting at ~ 4.75 µm. Ridge waveguides of 50 µm and 100 µm width were fabricated with both PCDFB and Fabry-Perot feedback mechanisms. The Fabry-Perot device has a broad emitting spectrum and a broad far-field character. The PCDFB devices have primarily a single spectral mode and a diffraction limited far field characteristic with a full angular width at half-maximum of 4.8 degrees and 2.4 degrees for the 50 µm and 100 µm ridge widths, respectively. [reprint (PDF)]
15.	Electron capture processes in optically excited In0.53Ga 0.47As/InP quantum wells U. Cebulla, G. Bacher, A. Forchel, D. Schmitz, H. Jürgensen, M. Razeghi Appl. Phys. Lett. 55, 933–935 (1989)-- September 4, 1989* ...[Visit Journal] We have performed picosecond time-resolved measurements on Ir:.O. 53 GaO. 47 As/lnP quantum wells with varying barrier thicknesses using 10 ps Nd:Y AG excitation. For this excitation, holes and electrons are created in the Ino . 53 GaOA7 As layers. Due to momentum conservation the Nd:YAG excitation accelerates the electrons above the InP barrier where they can diffuse but cannot recombine. By examining the rise time of the quantum well emission, we can show that for samples with thick barriers, the harrier geometry largely controls the dynamic properties of the carriers after Nd:YAG excitation. [reprint (PDF)]
15.	Single-mode, high-power, midinfrared, quantum cascade laser phased arrays Wenjia Zhou , Donghai Wu , Quan-Yong Lu, Steven Slivken & Manijeh Razeghi Scientific Reports 8:14866-- October 5, 2018 ...[Visit Journal] We demonstrate single-mode, 16-channel, optical phased arrays based on quantum cascade laser technology, with emission wavelengths around 4.8 μm. The integrated device consists of a distributed feedback seed section, a highly-efficient tree array multi-mode interferometer power splitter, and a 16-channel amplifier array with a 4° angled facet termination. With a single layer Y₂O₃ coating, the angled facet reflectivity is estimated to be less than 0.1% for suppressing amplifier self-lasing. A peak output power of 30 W is achieved with an emission spectrum narrower than 11 nm and a side mode suppression ratio over 25 dB. Far field distribution measurement result indicates a uniform phase distribution across the array output. Using the same phased array architecture, we also demonstrate single-mode 3.8 μm QCL amplifier arrays with up to 20 W output power. [reprint (PDF)]
15.	Investigation of MgZnO/ZnO heterostructures grown on c-sapphire substrates by pulsed laser deposition D. J. Rogers ; F. Hosseini Teherani ; P. Bove ; A. Lusson ; M. Razeghi Proc. SPIE 8626, Oxide-based Materials and Devices IV, 86261X (March 18, 2013)-- March 18, 2013 ...[Visit Journal] MgZnO thin films were grown on c-sapphire and ZnO-coated c-sapphire substrates by pulsed laser deposition from a ZnMgO target with 4 at% Mg. The MgZnO grown on the ZnO underlayer showed significantly better crystal quality than that grown directly on sapphire. AFM studies revealed a significant deterioration in surface morphology for the MgZnO layers compared with the ZnO underlayer. Optical transmission studies indicated a MgZnO bandgap of 3.61eV (compared with 3.34eV for the ZnO), which corresponds to a Mg content of about 16.1 at%. The MgZnO/ZnO heterojunction showed an anomalously low resistivity, which was more than two orders of magnitude less than the MgZnO layer and an order of magnitude lower than that for the ZnO layer. It was suggested that this may be attributable to the presence of a 2D electron gas at the ZnMgO/ZnO heterointerface. [reprint (PDF)]
15.	High-detectivity quantum-dot infrared photodetectors grown by metal-organic chemical-vapor deposition J. Szafraniec, S. Tsao, W. Zhang, H. Lim, M. Taguchi, A.A. Quivy, B. Movaghar and M. Razeghi Applied Physics Letters 88 (121102)-- March 20, 2006 ...[Visit Journal] A mid-wavelength infrared photodetector based on InGaAs quantum dots buried in an InGaP matrix and deposited on a GaAs substrate was demonstrated. Its photoresponse at T=77 K was measured to be around 4.7 μm with a cutoff at 5.5 μm. Due to the high peak responsivity of 1.2 A/W and low dark-current noise of the device, a specific peak detectivity of 1.1 x 10¹² cm·Hz^½·W⁻¹ was achieved at −0.9 V bias [reprint (PDF)]
15.	Status of III-V semiconductor thin films and their applications to future OEICs Manijeh Razeghi Proc. SPIE 10267, Integrated Optics and Optoelectronics, 102670T -- June 26, 2017 ...[Visit Journal] In the last decade, semiconductor technology has been advanced to a great extent in terms of electronic and photonic discrete devices. One of the main reasons for such a progress, is the result of advancement in the epitaxial growth techniques such as molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD), where device quality films can be grown with great control over composition, uniformity and thickness. MOCVD has proven to be one of the best growth methods for many IH-V semiconductor thin films 1. Its flexibility and potential to yield a broad range of growth rates resulted in the layers featuring the thicknesses from tens of microns down to several nanometers. Planar structures containing quantum wells with atomically flat interfaces, superlattices, strained or graded-index layers were successfully grown by MOCVD. Furthermore, MOCVD proved its efficiency in producing a laser devices by overgrowth and epitaxy on patterned substrates. The importance of MOCVD is strongly enhanced by the possibility of large-scale production by simultaneous growth on several substrates in one process. Several III-V semiconductor films with bandgaps ranging from infrared to ultraviolet (15 to 0.2 μm) have been successfully grown by MOCVD. [reprint (PDF)]
15.	Recent advances in MOCVD growth of InxGa1-xAsyP1-y alloys M. Razeghi, J.P. Duchemin M. Razeghi, J.P. Duchemin, Recent advances in MOCVD growth of InxGa1-xAsyP1-y alloys, Journal of Crystal Growth, Volume 70, Issues 1–2, 1984, Pages 145-149,-- December 1, 1984 ...[Visit Journal] The low pressure metalorganic chemical vapour deposition (LPMOCVD) growth of GaxIn1-xAsyP1-y-InP lattice matched system, with high mobilities, sharp interfaces, low background doping densities, and the formation of a two-dimensional electron gas (2DEG) at the interfaces, has recently made spectacular advances, as in evidenced by the availability of high quality DH lasers, PIN photodiodes, and Gunn diodes. We present here some new results obtained on the above-mentioned material and devices. [reprint (PDF)]
15.	Optical Investigations of GaAs-GaInP Quantum Wells and Superlattices Grown by Metalorganic Chemical Vapor Deposition Omnes F., and Razeghi M. Applied Physics Letters 59 (9), p. 1034-- May 28, 1991 ...[Visit Journal] Recent experimental results on the photoluminescence and photoluminescence excitation of GaAs‐Ga_0.51In_0.49P lattice‐matched quantum wells and superlattices are discussed. The full width at half maximum of a 10‐period GaAs‐GaInP superlattice with Lz=90 Å and LB=100 Å is 4 meV at 4 K. The photoluminescence excitation exhibits very sharp peaks attributed to the electron to light‐hole and electron to heavy‐hole transitions. The GaInP‐GaAs interface suffers from memory effect of In, rather than P or As elements. [reprint (PDF)]
15.	A hybrid green light-emitting diode comprised of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN C. Bayram, F. Hosseini Teherani, D.J. Rogers and M. Razeghi Applied Physics Letters, Vol. 93, No. 8, p. 081111-1-- August 25, 2008 ...[Visit Journal] Hybrid green light-emitting diodes (LEDs) comprised of n-ZnO/(InGaN/GaN) multi-quantum-wells/p-GaN were grown on semi-insulating AlN/sapphire using pulsed laser deposition for the n-ZnO and metal organic chemical vapor deposition for the other layers. X-ray diffraction revealed that high crystallographic quality was preserved after the n-ZnO growth. LEDs showed a turn-on voltage of 2.5 V and a room temperature electroluminescence (EL) centered at 510 nm. A blueshift and narrowing of the EL peak with increasing current was attributed to bandgap renormalization. The results indicate that hybrid LED structures could hold the prospect for the development of green LEDs with superior performance. [reprint (PDF)]
15.	Reliability of Aluminum-Free 808 nm High-Power Laser Diodes with Uncoated Mirrors I. Eliashevich, J. Diaz, H. Yi, L. Wang, and M. Razeghi Applied Physics Letters 66 (23)-- June 5, 1995 ...[Visit Journal] The reliability of uncoated InGaAsP/GaAs high‐power diode lasers emitting at 808 nm wavelength has been studied. 47 W of quasicontinuous wave output power (pulse width 200 μs, frequency 20 Hz) have been obtained from a 1 cm wide laser bar. A single‐stripe diode without mirror coating has been life tested at 40 °C for emitting power of 800 mW continuous wave (cw) and showed no noticeable degradation and no change of the lasing wavelength after 6000 h of operation. [reprint (PDF)]
15.	Monolithic terahertz source Q. Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai and M. Razeghi Nature Photonics \| Research Highlights -- July 31, 2014 ...[Visit Journal] To date, the production of continuous-wave terahertz (THz) sources based on intracavity difference-frequency generation from mid-infrared quantum cascade lasers operating at room temperature has proved elusive. A critical problem is that, to achieve a large nonlinear susceptibility for frequency conversion, the active region of the quantum cascade laser requires high doping, which elevates the lasing threshold current density. Now, Quan-Yong Lu and colleagues from Northwestern University in the USA have overcome this problem and demonstrated a room-temperature continuous-wave THz source based on difference-frequency generation in quantum cascade lasers. They designed quantum-well structures based on In_0.53Ga_0.47As/In_0.52Al_0.48As material system for two mid-infrared wavelengths. The average doping in the active region was about 2.5 × 10¹⁶ cm⁻³. A buried ridge, buried composite distributed-feedback waveguide with the Čerenkov phase-matching scheme was used to reduce the waveguide loss and enhance heat dissipation. As a result, single-mode emission at 3.6 THz was observed at 293 K. The continuous-wave THz power reached 3 μW with a conversion efficiency of 0.44 mW W⁻² from mid-infrared to THz waves. Using a similar device design, a THz peak power of 1.4 mW was achieved in pulse mode. [reprint (PDF)]
15.	Characterization of high quality GaInP/GaAs superlattices grown on GaAs and Si substrates by gas source molecular beam epitaxy C. Jelen, S. Slivken, X.G. He, and M. Razeghi and S. Shastry Journal of Vacuum Science and Technology B 12 (2)-- March 1, 1994 ...[Visit Journal] We report an analysis of the heteroepitaxial interfaces in high quality GaInP–GaAs superlattices grown simultaneously on GaAs and Si substrates by gas source molecular beam epitaxy. These two superlattices have been studied using high resolution x-ray diffraction measurements. Sharp superlattice satellites, with very little broadening, are observed within a 6° range for the sample on GaAs. Photoluminescence peaks with full widths at half-maximums of 5 and 7 meV are obtained at 4 K for samples with 58 Å wells on GaAs and Si, respectively. Room temperature exciton absorption is observed in the photovoltage measurements for a superlattice grown on Si substrate. The thicknesses determined by x-ray analysis are consistent with those obtained by a Kronig–Penny model fitting of the photovoltage spectroscopy. [reprint (PDF)]
15.	Negative and positive luminescence in mid-wavelength infrared InAs/GaSb superlattice photodiodes D. Hoffman, A. Gin, Y. Wei, A. Hood, F. Fuchs, and M. Razeghi IEEE Journal of Quantum Electronics, 41 (12)-- December 1, 2005 ...[Visit Journal] The quantum efficiency of negative and positive luminescence in binary type-II InAs-GaSb superlattice photodiodes has been investigated in the midinfrared spectral range around the 5-μm wavelength. The negative luminescence efficiency is nearly independent on temperature in the entire range from 220 to 325 K. For infrared diodes with a 2-μm absorbing layer, processed without anti-reflection coating, a negative luminescence efficiency of 45% is found, indicating very efficient minority carrier extraction. The temperature dependent measurements of the quantum efficiency of the positive luminescence enables for the determination of the capture cross section of the Shockley-Read-Hall centers involved in the competing nonradiative recombination. [reprint (PDF)]
15.	Solar-blind AlGaN photodiodes with very low cutoff wavelength D. Walker, V. Kumar, K. Mi, P. Sandvik, P. Kung, X.H. Zhang, and M. Razeghi Applied Physics Letters 76 (4)-- January 24, 2000 ...[Visit Journal] We report the fabrication and characterization of AlxGa1–xN photodiodes (x~0.70) grown on sapphire by low-pressure metalorganic chemical vapor deposition. The peak responsivity for –5 V bias is 0.11 A/W at 232 nm, corresponding to an internal quantum efficiency greater than 90%. The device response drops four orders of magnitude by 275 nm and remains at low response for the entire near-ultraviolet and visible spectrum. Improvements were made to the device design including a semitransparent Ni/Au contact layer and a GaN:Mg cap layer, which dramatically increased device response by enhancing the carrier collection efficiency. [reprint (PDF)]
15.	Gallium nitride on silicon for consumer & scalable photonics C. Bayram, K.T. Shiu, Y. Zhu, C.W. Cheng, D.K. Sadana, Z. Vashaei, E. Cicek, R. McClintock and M. Razeghi SPIE Proceedings, Vol. 8631, p. 863112-1, Photonics West, San Francisco, CA-- February 4, 2013 ...[Visit Journal] Gallium Nitride (GaN) is a unique material system that has been heavily exploited for photonic devices thanks to ultraviolet-to-terahertz spectral tunability. However, without a cost effective approach, GaN technology is limited to laboratory demonstrations and niche applications. In this investigation, integration of GaN on Silicon (100) substrates is attempted to enable widespread application of GaN based optoelectronics. Controlled local epitaxy of wurtzite phase GaN on on-axis Si(100) substrates is demonstrated via metal organic chemical vapor deposition (MOCVD). CMOS-compatible fabrication scheme is used to realize [SiO2-Si{111}-Si{100}] groove structures on conventional 200-mm Si(100) substrates. MOCVD growth (surface treatment, nucleation, initiation) conditions are studied to achieve controlled GaN epitaxy on such grooved Si(100) substrates. Scanning electron microscopy and transmission electron microscopy techniques are used to determine uniformity and defectivity of the GaN. Our results show that aforementioned groove structures along with optimized MOCVD growth conditions can be used to achieve controlled local epitaxy of wurtzite phase GaN on on-axis Si(100) substrates. [reprint (PDF)]
15.	Room-temperature continuous wave operation of distributed feedback quantum cascade lasers with watt-level power output Q.Y. Lu, Y. Bai, N. Bandyopadhyay, Sl Slivken, and M. Razeghi Applied Physics Letters, Vol. 97, No. 23, p. 231119-1-- December 6, 2010 ...[Visit Journal] We demonstrate surface-grating distributed feedback quantum cascade lasers (QCLs) with a watt-level power output at 4.75 μm. A device with a 5 mm cavity length exhibits an output power of 1.1 W in room-temperature cw operation. Single-mode operation with a side mode suppression ratio of 30 dB is obtained in the working temperature of 15–105 °C. A double-lobed far field with negligible beam steering is observed. The significance of this demonstration lies in its simplicity and readiness to be applied to standard QCL wafers with the promise of high-power performances. [reprint (PDF)]
15.	High performance quantum dot-quantum well infrared focal plane arrays S. Tsao, A. Myzaferi, and M. Razeghi SPIE Proceedings, San Francisco, CA (January 22-28, 2010), Vol. 7605, p. 76050J-1-- January 27, 2010 ...[Visit Journal] Quantum dot (QD) devices are a promising technology for high operating temperature detectors. We have studied InAs QDs embedded in an InGaAs/InAlAs quantum well structure on InP substrate for middle wavelength infrared detectors and focal plane arrays (FPAs). This combined dot-well structure has weak dot confinement of carriers, and as a result, the device behavior differs significantly from that in more common dot systems with stronger confinement. We report on our studies of the energy levels in the QDWIP devices and on QD-based detectors operating at high temperature with D* over 10¹⁰ cm·Hz^½/W at 150 K operating temperature and high quantum efficiency over 50%. FPAs have been demonstrated operating at up to 200 K. We also studied two methods of adapting the QDWIP device to better accommodate FPA readout circuit limitations. [reprint (PDF)]
15.	Widely tuned room temperature terahertz quantum cascade laser sources Q.Y. Lu, N. Bandyopadhyay, S. Slivken, Y. Bai and M. Razeghi SPIE Proceedings, Vol. 8631, p. 863108-1, Photonics West, San Francisco, CA-- February 3, 2013 ...[Visit Journal] Room temperature THz quantum cascade laser sources with a broad spectral coverage based on intracavity difference frequency generation are demonstrated. Two mid-infrared active cores in the longer mid-IR wavelength range (9-11 micron)based on the single-phonon resonance scheme are designed with a second-order difference frequency nonlinearity specially optimized for the high operating fields that correspond to the highest mid-infrared output powers. A Čerenkov phase-matching scheme along with integrated dual-period distributed feedback gratings are used for efficient THz extraction and spectral purification. Single mode emissions from 1.0 to 4.6 THz with a side-mode suppression ratio and output power up to 40 dB and 32 μW are obtained, respectively. [reprint (PDF)]

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