Center for Quantum Devices - Most Downloaded Journal Articles

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1.	Optical Absorption and Photoresponse in fully Quaternary p-type Quantum Well Detectors J. Hoff, C. Jelen, S. Slivken, G.J. Brown, and M. Razeghi SPIE Photonics West '96 Photodetectors: Materials and Devices; Proceedings 2685-- January 27, 1996 ...[Visit Journal] Acceptor doped, non-strained aluminum-free Quantum Well Intersubband Photodetectors lattice matched to GaAs with Ga_0.79In_0.21As_0.59P_0.41 wells and Ga_0.62In_0.38As_0.22P_0.78 barriers have been demonstrated on semi-insulating GaAs substrates. These devices which operate at normal incidence demonstrate a unique spectral response which extends from approximately 2 μm up to 10 μm. To explain such a broad spectral shape, a detailed theoretical analysis based on the 8 x 8 Kane Hamiltonian was necessary to probe all aspect of optical absorption. The results of this analysis revealed that spectral shape results from the influence of the Spin Split-off band on the band structure and the optical matrix. [reprint (PDF)]
1.	Highly Conductive Co-Doped Ga2O3Si-In Grown by MOCVD Junhee Lee, Honghyuk Kim, Lakshay Gautam and Manijeh Razeghi Coatings 2021, 11(3), 287; https://doi.org/10.3390/coatings11030287 ...[Visit Journal] We report a highly conductive gallium oxide doped with both silicon and indium grown on c-plane sapphire substrate by MOCVD. From a superlattice structure of indium oxide and gallium oxide doped with silicon, we obtained a highly conductive material with an electron hall mobility up to 150 cm2/V·s with the carrier concentration near 2 × 1017 cm−3. However, if not doped with silicon, both Ga2O3:In and Ga2O3 are highly resistive. Optical and structural characterization techniques such as X-ray, transmission electron microscope, and photoluminescence, reveal no significant incorporation of indium into the superlattice materials, which suggests the indium plays a role of a surfactant passivating electron trapping defect levels. [reprint (PDF)]
1.	Quantum cascade lasers that emit more light than heat Y. Bai, S. Slivken, S. Kuboya, S.R. Darvish and M. Razeghi Nature Photonics, February 2010, Vol. 4, p. 99-102-- February 1, 2010 ...[Visit Journal] For any semiconductor lasers, the wall plug efficiency, that is, the portion of the injected electrical energy that can be converted into output optical energy, is one of the most important figures of merit. A device with a higher wall plug efficiency has a lower power demand and prolonged device lifetime due to its reduced self-heating. Since its invention, the power performance of the quantum cascade laser has improved tremendously. However, although the internal quantum efficiency can be engineered to be greater than 80% at low temperatures, the wall plug efficiency of a quantum cascade laser has never been demonstrated above 50% at any temperature. The best wall plug efficiency reported to date is 36% at 120 K. Here, we overcome the limiting factors using a single-well injector design and demonstrate 53% wall plug efficiency at 40 K with an emitting wavelength of 5 µm. In other words, we demonstrate a quantum cascade laser that produces more light than heat. [reprint (PDF)]
1.	High Power Quantum Cascade Lasers (QCLs) Grown by GasMBE M. Razeghi and S. Slivken SPIE Proceedings, International Conference on Solid State Crystals (ICSSC), Zakopane, Poland, -- October 14, 2002 ...[Visit Journal] This paper is a brief summary of the technological development and state-of-the-art performance of quantum cascade lasers produced at the Centre for Quantum Devices. Laser design will be discussed, as well as experimental details of device fabrication. Recent work has focused on the development of high peak and average power QCLs emitting at room temperature and above. Scaling of the output is demonstrated by increasing the number of emitting regions in the waveguide core. At λ = 9 µm, over 7 W of peak power has been demonstrated at room temperature for a single diode, with an average power of 300 mW at 6% duty cycle. At shorter wavelengths, laser development includes the use of highly strain-balanced heterostructures in order to maintain a high conduction band offset and minimize leakage current. At λ = 6 µm, utilizing a high reflective coating and epilayer-down mounting of the laser, we have demonstrated 225 mW of average power from a single facet at room temperature. Lastly, these results are put in perspective of other reported results and possible future directions are discussed. [reprint (PDF)]
1.	Background limited performance of long wavelength infrared focal plane arrays fabricated from M-structure InAs-GaSb superlattices P.Y. Delaunay, B.M. Nguyen, D. Hoffman, E.K. Huang, and M. Razeghi IEEE Journal of Quantum Electronics, Vol. 45, No. 2, p. 157-162.-- February 1, 2009 ...[Visit Journal] The recent introduction of a M-structure design improved both the dark current and R₀A performances of Type-II InAs-GaSb photodiodes. A focal plane array fabricated with this design was characterized at 81 K. The dark current of individual pixels was measured between 1.1 and 1.6 nA, 7 times lower than previous superlattice FPAs. This led to a higher dynamic range and longer integration times. The quantum efficiency of detectors without antireflective coating was 74%. The noise equivalent temperature difference reached 23 mK, limited only by the performance of the testing system and the read out integrated circuit. Background limited performances were demonstrated at 81 K for a 300 K background. [reprint (PDF)]
1.	The Molecular Beam Epitaxial Growth of InSb on (111) GaAs E. Michel, J. Kim, J. Xu, S. Javadpour, I. Ferguson, and M. Razeghi Applied Physics Letters 69 (2)-- July 8, 1996 ...[Visit Journal] The molecular beam epitaxial growth of InSb on (111)B GaAs has been investigated. It was found that for a given Sb/In ratio, a higher growth temperature was required for the growth of InSb on (111)B GaAs compared to that on (001) GaAs. This difference has been attributed to the bonding characteristics of the (111)B and (001) surface. Once growth had been optimized, it was found that the material characteristics of (111)B InSb were almost identical to that of (001) InSb, i.e., independent of orientation. For example, the x-ray full width at half-maximum and 300 K mobility had the same absolute values for (111) InSb and (001)InSb and followed the same dependence with the sample thickness. Te was found to be a well-behaved n-type dopant for (111)B InSb. [reprint (PDF)]
1.	Aluminum nitride films on different orientations of sapphire and silicon K. Dovidenko, S. Oktyabrsky, J. Narayan, and M. Razeghi Journal of Applied Physics79 (5)-- March 1, 1996 ...[Visit Journal] The details of epitaxial growth and microstrictural characteristics of AlN films grown on sapphire (0001), (1012) and Si (100), (111) substrates were investigated using plan‐view and cross‐sectional high‐resolution transmission electron microscopy and x‐ray diffraction techniques. The films were grown by metalorganic chemical vapor deposition using TMA1+NH3+N2 gas mixtures. Different degrees of epitaxy were observed for the films grown on α‐Al₂O₃ and Si substrates in different orientations. The epitaxial relationship for (0001) sapphire was found to be (0001)AlN∥(0001)sap with in‐plane orientation relationship of [0110]AlN∥[1210]sap. This is equivalent to a 30° rotation in the basal (0001) plane. For (1012) sapphire substrates, the epitaxial relationship was determined to be (1120)AlN∥(1012)sap with the in‐plane alignment of [0001]AlN∥[1011]sap. The AlN films on (0001) α‐Al₂O₃ were found to contain inverted domain boundaries and a/3〈1120〉 threading dislocations with the estimated density of 10¹⁰ cm⁻². The density of planar defects (stacking faults) found in AlN films was considerably higher in the case of (1012) compared to (0001) substrates. Films on Si substrates were found to be highly textured c axis oriented when grown on (111) Si, and c axis textured with random in‐plane orientation on (100) Si. The role of thin‐film defects and interfaces on device fabrication is discussed. [reprint (PDF)]
1.	Room Temperature Operation of InTlSb Infrared Photodetectors on GaAs J.D. Kim, E. Michel, S. Park, J. Xu, S. Javadpour and M. Razeghi Applied Physics Letters 69 (3)-- August 15, 1996 ...[Visit Journal] Long-wavelength InTlSb photodetectors operating at room temperature are reported. The photo- detectors were grown on (100) semi-insulating GaAs substrates by low-pressure metalorganic chemical vapor deposition. Photoresponse of InTlSb photodetectors is observed up to 11 µm at room temperature. The maximum responsivity of an In_0.96Tl_0.04Sb photodetector is about 6.64 V/W at 77 K, corresponding to a detectivity of about 7.64 × 10⁸ cm·Hz^½/W. The carrier lifetime in InTlSb photodetectors derived from the stationary photoconductivity is 10–50 ns at 77 K. [reprint (PDF)]
1.	High Temperature Continuous Wave Operation of ~8 μm Quantum Cascade Lasers S. Slivken, A. Matlis, C. Jelen, A. Rybaltowski, J. Diaz, and M. Razeghi Applied Physics Letters 74 (2)-- January 11, 1999 ...[Visit Journal] We report single-mode continuous-wave operation of a λ∼8 μm quantum cascade laser at 140 K. The threshold current density is 4.2 kA/cm² at 300 K in pulsed mode and 2.5 kA/cm² at 140 K in continuous wave for 2 mm long index-guided laser cavities of 20 μm width. Wide stripe (W ∼ 100 μm), index-guided lasers from the same wafer in pulsed operation demonstrate an average T₀ of 210 K with other wafers demonstrating a T₀ as high as 290 K for temperatures from 80 to 300 K. This improvement in high-temperature performance is a direct result of three factors: excellent material quality, a low-loss waveguide design, and a low-leakage index-guided laser geometry. [reprint (PDF)]
1.	Monolithic, steerable, mid-infrared laser realized with no moving parts Slivken S, Wu D, Razeghi M Scientific Reports 7, 8472 -- May 24, 2018 ...[Visit Journal] The mid-infrared (2.5 < λ < 25 μm) spectral region is utilized for many purposes, such as chemical/biological sensing, free space communications, and illuminators/countermeasures. Compared to near-infrared optical systems, however, mid-infrared component technology is still rather crude, with isolated components exhibiting limited functionality. In this manuscript, we make a significant leap forward in mid-infrared technology by developing a platform which can combine functions of multiple mid-infrared optical elements, including an integrated light source. In a single device, we demonstrate wide wavelength tuning (240 nm) and beam steering (17.9 degrees) in the mid-infrared with a significantly reduced beam divergence (down to 0.5 degrees). The architecture is also set up to be manufacturable and testable on a wafer scale, requiring no cleaved facets or special mirror coating to function. [reprint (PDF)]
1.	Intermixing of GaInP/GaAs Multiple Quantum Wells C. Francis, M.A. Bradley, P. Boucaud, F.H. Julien and M. Razeghi Applied Physics Letters 62 (2)-- January 11, 1993 ...[Visit Journal] The intermixing of GaInP‐GaAs superlattices induced by a heat treatment is investigated as a function of the annealing temperature and duration. Photoluminescence experiments reveal a large red shift of the effective band gap of the annealed quantum wells thus indicating a dominant self‐diffusion of the group III atoms which is confirmed by secondary ion mass spectroscopic measurements. For long enough annealing durations, the red shift saturates and even decreases due to the competing slower self‐diffusion of the group V atoms. Experiments are well understood based on a simple diffusion model. [reprint (PDF)]
1.	First cw operation of a Ga0.25In0.75As0.5P0.5‐InP laser on a silicon substrate M. Razeghi; M. Defour; R. Blondeau; F. Omnes; P. Maurel; O. Acher; F. Brillouet; J. C. C‐Fan; J. Salerno Appl. Phys. Lett. 53, 2389–2390 (1988) -- December 12, 1988 ...[Visit Journal] We report the first successful room-temperature cw operations of a GaO. 25 1110.75 ASo. 5 po. s -InP buried ridge structure laser emitting at 1.3 f-tm grown by two-step low-pressure metalorganic chemical vapor deposition on a silicon substrate. An output power of 20 m W with an external quantum efficiency of 16% at room temperature has been obtained. A threshold current as low as 45 rnA under cw operation at room temperature has been measured. The first cw aging test at room temperature, at 2 mW during 5 h, shows a very low degradation (Ill 11,;;5%). [reprint (PDF)]
1.	Tl incorporation in InSb and lattice contraction of In_1-xTl_xSb J.J. Lee and M. Razeghi Applied Physics Letters 76 (3)-- January 17, 2000 ...[Visit Journal] Ternary In_1−xTl_xSb thin films are grown by low pressure metalorganic chemical vapor deposition in the high In composition region. Infrared photoresponse spectra of the In_1−xTl_xSb epilayers show a clear shift toward a longer wavelength compared to that of InSb. Tl incorporation is confirmed by Auger electron spectroscopy. In contrast to the theoretical expectation, high resolution x-ray diffraction study reveals that the lattice of the In_1−xTl_xSb epilayers is contracted by the incorporation of Tl. As more Tl is incorporated, the lattice contraction is observed to increase gradually in the experimental range. A possible origin of this phenomenon is discussed. Our experimental results suggest that the Tl incorporation behavior in In_1−xTl_xSb differs from that of other group III impurities in III antimonides. [reprint (PDF)]
1.	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)]
1.	High performance Zn-diffused planar mid-wavelength infrared type-II InAs/InAs_1-xSb_x superlattice photodetector by MOCVD Donghai Wu, Arash Dehzangi, Jiakai Li, and Manijeh Razeghi Appl. Phys. Lett. 116, 161108-- April 21, 2020 ...[Visit Journal] We report a Zn-diffused planar mid-wavelength infrared photodetector based on type-II InAs/InAs_1-xSb_x superlattices. Both the superlattice growth and Zn diffusion were performed in a metal-organic chemical vapor deposition system. At 77K, the photodetector exhibits a peak responsivity of 0.70A/W at 3.65λ, corresponding to a quantum efﬁciency of 24% at zero bias without anti-reﬂection coating, with a 50% cutoff wavelength of 4.28λ. With an R₀A value of 3.2x10⁵ Ω·cm² and a dark current density of 9.6x10^-8 A/cm² bias of -20mV at 77K, the photodetector exhibits a speciﬁc detectivity of 2.9x10¹²cm·Hz^½/W. At 150K, the photodetector exhibits a dark current density of 9.1x10^-6 A/cm² and a quantum efﬁciency of 25%, resulting in a detectivity of 3.4x10¹¹cm·Hz/W. [reprint (PDF)]
1.	Investigation of Enhanced Heteroepitaxy and Electrical Properties in k-Ga2O3 due to Interfacing with β-Ga2O3 Template Layers Junhee Lee, Lakshay Gautam, Ferechteh H. Teherani, Eric V. Sandana, P. Bove, David J. Rogers and Manijeh Razeghi J. Lee, M. Razeghi, Physica Status Solidi A 2023,220, 2200559, https://doi.org/10.1002/pssa.202200559 ...[Visit Journal] Heteroepitaxial k-Ga2O3 films grown by metal-organic chemical vapor deposition (MOCVD) were found to have superior materials and electrical properties thanks to the interfacing with a b-Ga2O3 template layer. k-Ga2O3grown on sapphire has not been able to demonstrate its full potential due to materials imperfections created by strain induced by the lattice mismatch at the interface between the epilayer and the substrate. By adopting a b-Ga2O3 template on a c-sapphire substrate, higher quality k-Ga2O3thin films were obtained, as evidenced by a smoother surface morphology, narrower XRD peaks, and superior electrical performance. The implications of this phenomenon, caused by b-Ga2O3 buffer layer, are already very encouraging for both boosting current device performance and opening up the perspective of novel applications for Ga2O3. [reprint (PDF)]

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