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Sample records for grown bulk ingaas

  1. Multilayers of InGaAs Nanostructures Grown on GaAs(210) Substrates

    PubMed Central

    2010-01-01

    Multilayers of InGaAs nanostructures are grown on GaAs(210) by molecular beam epitaxy. With reducing the thickness of GaAs interlayer spacer, a transition from InGaAs quantum dashes to arrow-like nanostructures is observed by atomic force microscopy. Photoluminescence measurements reveal all the samples of different spacers with good optical properties. By adjusting the InGaAs coverage, both one-dimensional and two-dimensional lateral ordering of InGaAs/GaAs(210) nanostructures are achieved. PMID:20676193

  2. Characterization of Si volume- and delta-doped InGaAs grown by molecular beam epitaxy

    SciTech Connect

    Fedoryshyn, Y.; Kaspar, P.; Jaeckel, H.; Beck, M.

    2010-05-15

    Bulk InGaAs layers were grown at 400 deg. C lattice-matched to InP semi-insulating substrates by molecular beam epitaxy. Si doping of the layers was performed by applying volume- and delta-doping techniques. The samples were characterized by capacitance-voltage, van der Pauw-Hall, secondary ion mass spectroscopy and photoluminescence measurements. Good agreement in terms of dependence of mobility and Burstein-Moss shift shift on doping concentration in samples doped by the two different techniques was obtained. Amphoteric behavior of Si was observed at doping concentrations higher than {approx}2.9x10{sup 19} cm{sup -3} in both delta- and volume-doped samples. Degradation of InGaAs crystalline quality occurred in samples with Si concentrations higher than {approx}4x10{sup 19} cm{sup -3}.

  3. Lattice mismatched InGaAs on silicon photodetectors grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Papanicolaou, N. A.; Anderson, G. W.; Iliadis, A. A.; Christou, A.

    1993-02-01

    In0.5Ga0.5As on silicon photodetectors, including three types of interdigitated-finger devices as well as linear photoconductors, were fabricated and measured. The InGaAs/Si structure was grown by molecular beam epitaxy and utilized a 100 Å GaAs intervening nucleation layer between the silicon substrate and the InGaAs layers, step-graded InxGa1-xAs layers, and an in-situ grown 40 Å thick GaAs surface layer, which substantially enhanced the metal-semiconductor barrier height (Φb = 0.67 V) for the InGaAs. Schottky diodes fabricated independently of the photodetectors had nearly ideal characteristics with an ideality factor (n) of 1.02 and a reverse breakdown voltage of 40 V. The interdigitated Schottky photodetectors showed dark currents between <3nA and 54 μA at a 3 V bias and initial photoresponse rise times in the range of 600 to 725 ps, comparable to similar InGaAs metal-semiconductor-metal photodetectors grown lattice matched on InP. The photoconductors fabricated in the same material had rise times in the range of 575 to 1300 ps, thus being slightly slower, and had dark currents of 7 to 80 mA. The responsivity of the photoconductors was typically greater than that of the diodes by a factor of five to fifteen. The results show potential for monolithic integration of InGaAs photodetectors on silicon substrates.

  4. Spatially correlated structural and optical characterization of a single InGaAs quantum well fin selectively grown on Si by microscopy and cathodoluminescence techniques

    NASA Astrophysics Data System (ADS)

    David, S.; Roque, J.; Rochat, N.; Bernier, N.; Piot, L.; Alcotte, R.; Cerba, T.; Martin, M.; Moeyaert, J.; Bogumilowizc, Y.; Arnaud, S.; Bertin, F.; Bassani, F.; Baron, T.

    2016-05-01

    Structural and optical properties of InGaAs quantum well fins (QWFs) selectively grown on Si using the aspect ratio trapping (ART) method in 200 nm deep SiO2 trenches are studied. A new method combining cathodoluminescence, transmission electron microscopy, and precession electron diffraction techniques is developed to spatially correlate the presence of defects and/or strain with the light emission properties of a single InGaAs QWF. Luminescence losses and energy shifts observed at the nanoscale along InGaAs QWF are correlated with structural defects. We show that strain distortions measured around threading dislocations delimit both high and low luminescent areas. We also show that trapped dislocations on SiO2 sidewalls can also result in additional distortions. Both behaviors affect optical properties of QWF at the nanoscale. Our study highlights the need to improve the ART growth method to allow integration of new efficient III-V optoelectronic components on Si.

  5. Generation of continuous wave terahertz frequency radiation from metal-organic chemical vapour deposition grown Fe-doped InGaAs and InGaAsP

    NASA Astrophysics Data System (ADS)

    Mohandas, Reshma A.; Freeman, Joshua R.; Rosamond, Mark C.; Hatem, Osama; Chowdhury, Siddhant; Ponnampalam, Lalitha; Fice, Martyn; Seeds, Alwyn J.; Cannard, Paul J.; Robertson, Michael J.; Moodie, David G.; Cunningham, John E.; Davies, A. Giles; Linfield, Edmund H.; Dean, Paul

    2016-04-01

    We demonstrate the generation of continuous wave terahertz (THz) frequency radiation from photomixers fabricated on both Fe-doped InGaAs and Fe-doped InGaAsP, grown by metal-organic chemical vapor deposition. The photomixers were excited using a pair of distributed Bragg reflector lasers with emission around 1550 nm, and THz radiation was emitted over a bandwidth of greater than 2.4 THz. Two InGaAs and four InGaAsP wafers with different Fe doping concentrations were investigated, with the InGaAs material found to outperform the InGaAsP in terms of emitted THz power. The dependencies of the emitted power on the photomixer applied bias, incident laser power, and material doping level were also studied.

  6. Control of asymmetric strain relaxation in InGaAs grown by molecular-beam epitaxy

    SciTech Connect

    France, R.; Ptak, A. J.; Jiang, C.-S.; Ahrenkiel, S. P.

    2010-05-15

    InGaAs strain relaxation is studied by an in situ multibeam optical stress sensor (MOSS). Strain relaxation during growth of InGaAs on GaAs occurs at different thicknesses and rates along the directions perpendicular to its misfit dislocations, [110] and [110]. We show the asymmetry of relaxation between these directions in real time by aligning the MOSS laser array along [110] and [110]. This asymmetric relaxation data from the MOSS correlates with both x-ray diffraction relaxation analysis and an estimation of the misfit dislocation density from transmission electron microscopy images. Lowering the V/III ratio or raising the growth temperature lowers the thickness of the onset of dislocation formation, changes the relaxation rate, lowers the final relaxation during 2 {mu}m of growth, and shifts the initial direction of relaxation from [110] to [110]. We identify two phases of relaxation that occur at different growth thicknesses. Lowering the V/III ratio changes the relative contribution of each of these phases to the total relaxation of the epilayer.

  7. Periodic Two-Dimensional GaAs and InGaAs Quantum Rings Grown on GaAs (001) by Droplet Epitaxy.

    PubMed

    Tung, Kar Hoo Patrick; Huang, Jian; Danner, Aaron

    2016-06-01

    Growth of ordered GaAs and InGaAs quantum rings (QRs) in a patterned SiO2 nanohole template by molecular beam epitaxy (MBE) using droplet epitaxy (DE) process is demonstrated. DE is an MBE growth technique used to fabricate quantum nanostructures of high crystal quality by supplying group III and group V elements in separate phases. In this work, ordered QRs grown on an ordered nanohole template are compared to self-assembled QRs grown with the same DE technique without the nanohole template. This study allows us to understand and compare the surface kinetics of Ga and InGa droplets when a template is present. It is found that template-grown GaAs QRs form clustered rings which can be attributed to low mobility of Ga droplets resulting in multiple nucleation sites for QR formation when As is supplied. However, the case of template-grown InGaAs QRs only one ring is formed per nanohole; no clustering is observed. The outer QR diameter is a close match to the nanohole template diameter. This can be attributed to more mobile InGa droplets, which coalesce from an Ostwald ripening to form a single large droplet before As is supplied. Thus, well-patterned InGaAs QRs are demonstrated and the kinetics of their growth are better understood which could potentially lead to improvements in the future devices that require the unique properties of patterned QRs. PMID:27427737

  8. InGaAs Quantum Well Grown on High-Index Surfaces for Superluminescent Diode Applications

    PubMed Central

    2010-01-01

    The morphological and optical properties of In0.2Ga0.8As/GaAs quantum wells grown on various substrates are investigated for possible application to superluminescent diodes. The In0.2Ga0.8As/GaAs quantum wells are grown by molecular beam epitaxy on GaAs (100), (210), (311), and (731) substrates. A broad photoluminescence emission peak (~950 nm) with a full width at half maximum (FWHM) of 48 nm is obtained from the sample grown on (210) substrate at room temperature, which is over four times wider than the quantum well simultaneously grown on (100) substrate. On the other hand, a very narrow photoluminescence spectrum is observed from the sample grown on (311) with FWHM = 7.8 nm. The results presented in this article demonstrate the potential of high-index GaAs substrates for superluminescent diode applications. PMID:20672090

  9. Widely tunable alloy composition and crystal structure in catalyst-free InGaAs nanowire arrays grown by selective area molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Treu, J.; Speckbacher, M.; Saller, K.; Morkötter, S.; Döblinger, M.; Xu, X.; Riedl, H.; Abstreiter, G.; Finley, J. J.; Koblmüller, G.

    2016-02-01

    We delineate the optimized growth parameter space for high-uniformity catalyst-free InGaAs nanowire (NW) arrays on Si over nearly the entire alloy compositional range using selective area molecular beam epitaxy. Under the required high group-V fluxes and V/III ratios, the respective growth windows shift to higher growth temperatures as the Ga-content x(Ga) is tuned from In-rich to Ga-rich InGaAs NWs. Using correlated x-ray diffraction, transmission electron microscopy, and micro-photoluminescence spectroscopy, we identify structural defects to govern luminescence linewidths in In-rich (x(Ga) < 0.4) and Ga-rich (x(Ga) > 0.6) NWs, whereas limitations at intermediate Ga-content (0.4 < x(Ga) < 0.6) are mainly due to compositional inhomogeneities. Most remarkably, the catalyst-free InGaAs NWs exhibit a characteristic transition in crystal structure from wurtzite to zincblende (ZB) dominated phase near x(Ga) ˜ 0.4 that is further reflected in a cross-over from blue-shifted to red-shifted photoluminescence emission relative to the band edge emission of the bulk ZB InGaAs phase.

  10. Effects of using As2 and As4 on the optical properties of InGaAs quantum rods grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Li, L. H.; Patriarche, G.; Linfield, E. H.; Khanna, S. P.; Davies, A. G.

    2010-11-01

    We investigate the effect of the arsenic source (As2 and As4) on the optical properties of InGaAs quantum rods (QRs) grown by molecular beam epitaxy. Owing to differences in the In and Ga diffusion lengths under As2 and As4 fluxes, photoluminescence (PL) peak energies of the QR samples depend strongly on the As source when similar growth conditions are used. A marked improvement in the PL intensities from QR samples grown using As4 is achieved. However, for both As2 and As4, an increase of the As overpressure results in a PL intensity degradation, probably due to the formation of nonradiative recombination centers.

  11. Comparative optical study of epitaxial InGaAs quantum rods grown with As{sub 2} and As{sub 4} sources

    SciTech Connect

    Nedzinskas, Ramūnas; Čechavičius, Bronislovas; Kavaliauskas, Julius; Karpus, Vytautas; Valušis, Gintaras; Li, Lianhe; Khanna, Suraj P.; Linfield, Edmund H.

    2013-12-04

    Photoreflectance and photoluminescence (PL) spectroscopies are used to examine the optical properties and electronic structure of InGaAs quantum rods (QRs), embedded within InGaAs quantum well (QW). The nanostructures studied were grown by molecular beam epitaxy using As{sub 2} or As{sub 4} sources. The impact of As source on spectral features associated with interband optical transitions in the QRs and the surrounding QW are demonstrated. A red shift of the QR- and a blue shift of the QW-related optical transitions, along with a significant increase in PL intensity, have been observed if an As{sub 4} source is used. The changes in optical properties are attributed mainly to carrier confinement effects caused by variation of In content contrast between the QR material and the surrounding well.

  12. Carbon nanotubes grown on bulk materials and methods for fabrication

    DOEpatents

    Menchhofer, Paul A.; Montgomery, Frederick C.; Baker, Frederick S.

    2011-11-08

    Disclosed are structures formed as bulk support media having carbon nanotubes formed therewith. The bulk support media may comprise fibers or particles and the fibers or particles may be formed from such materials as quartz, carbon, or activated carbon. Metal catalyst species are formed adjacent the surfaces of the bulk support material, and carbon nanotubes are grown adjacent the surfaces of the metal catalyst species. Methods employ metal salt solutions that may comprise iron salts such as iron chloride, aluminum salts such as aluminum chloride, or nickel salts such as nickel chloride. Carbon nanotubes may be separated from the carbon-based bulk support media and the metal catalyst species by using concentrated acids to oxidize the carbon-based bulk support media and the metal catalyst species.

  13. Optical properties of InGaAs linear graded buffer layers on GaAs grown by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lee, B.; Baek, J. H.; Lee, J. H.; Choi, S. W.; Jung, S. D.; Han, W. S.; Lee, E. H.

    1996-05-01

    We report optical characteristics of linear graded InxGa1-xAs (XIn=0-0.58) buffer layers grown on GaAs by low-pressure metalorganic chemical vapor deposition. Two types of wirelike surface structures were observed from the layers grown at two different temperatures. Low-temperature photoluminescence (PL) and double-crystal x-ray diffractometric measurements indicate that the PL energy and the relaxation of the graded layers were strongly dependent on the top surface structure. InGaAs cap layers were grown on top of the graded buffer layers with a variation of indium composition. A strong PL signal was observed from the top region of the graded layer grown with a lattice-matched cap layer. It suggests that the top region of the grade, similar to a graded well structure, is compressively strained but is of high structural quality without dislocations.

  14. Effect of InGaAs interlayer on the properties of GaAs grown on Si (111) substrate by molecular beam epitaxy

    SciTech Connect

    Wen, Lei; Gao, Fangliang; Li, Jingling; Guan, Yunfang; Wang, Wenliang; Zhou, Shizhong; Lin, Zhiting; Zhang, Xiaona; Zhang, Shuguang E-mail: mssgzhang@scut.edu.cn; Li, Guoqiang E-mail: mssgzhang@scut.edu.cn

    2014-11-21

    High-quality GaAs films have been epitaxially grown on Si (111) substrates by inserting an In{sub x}Ga{sub 1−x}As interlayer with proper In composition by molecular beam epitaxy (MBE). The effect of In{sub x}Ga{sub 1−x}As (0 < x < 0.2) interlayers on the properties of GaAs films grown on Si (111) substrates by MBE has been studied in detailed. Due to the high compressive strain between InGaAs and Si, InGaAs undergoes partial strain relaxation. Unstrained InGaAs has a larger lattice constant than GaAs. Therefore, a thin InGaAs layer with proper In composition may adopt a close lattice constant with that of GaAs, which is beneficial to the growth of high-quality GaAs epilayer on top. It is found that the proper In composition in In{sub x}Ga{sub 1−x}As interlayer of 10% is beneficial to obtaining high-quality GaAs films, which, on the one hand, greatly compensates the misfit stress between GaAs film and Si substrate, and on the other hand, suppresses the formation of multiple twin during the heteroepitaxial growth of GaAs film. However, when the In composition does not reach the proper value (∼10%), the In{sub x}Ga{sub 1−x}As adopts a lower strain relaxation and undergoes a lattice constant smaller than unstrained GaAs, and therefore introduces compressive stress to GaAs grown on top. When In composition exceeds the proper value, the In{sub x}Ga{sub 1−x}As will adopt a higher strain relaxation and undergoes a lattice constant larger than unstrained GaAs, and therefore introduces tensile stress to GaAs grown on top. As a result, In{sub x}Ga{sub 1−x}As interlayers with improper In composition introduces enlarged misfit stress to GaAs epilayers grown on top, and deteriorates the quality of GaAs epilayers. This work demonstrates a simple but effective method to grow high-quality GaAs epilayers and brings up a broad prospect for the application of GaAs-based optoelectronic devices on Si substrates.

  15. Low defect InGaAs quantum well selectively grown by metal organic chemical vapor deposition on Si(100) 300 mm wafers for next generation non planar devices

    NASA Astrophysics Data System (ADS)

    Cipro, R.; Baron, T.; Martin, M.; Moeyaert, J.; David, S.; Gorbenko, V.; Bassani, F.; Bogumilowicz, Y.; Barnes, J. P.; Rochat, N.; Loup, V.; Vizioz, C.; Allouti, N.; Chauvin, N.; Bao, X. Y.; Ye, Z.; Pin, J. B.; Sanchez, E.

    2014-06-01

    Metal organic chemical vapor deposition of GaAs, InGaAs, and AlGaAs on nominal 300 mm Si(100) at temperatures below 550 °C was studied using the selective aspect ratio trapping method. We clearly show that growing directly GaAs on a flat Si surface in a SiO2 cavity with an aspect ratio as low as 1.3 is efficient to completely annihilate the anti-phase boundary domains. InGaAs quantum wells were grown on a GaAs buffer and exhibit room temperature micro-photoluminescence. Cathodoluminescence reveals the presence of dark spots which could be associated with the presence of emerging dislocation in a direction parallel to the cavity. The InGaAs layers obtained with no antiphase boundaries are perfect candidates for being integrated as channels in n-type metal oxide semiconductor field effect transistor (MOSFET), while the low temperatures used allow the co-integration of p-type MOSFET.

  16. Low-temperature-grown InGaAs quantum wells for optical device applications

    NASA Astrophysics Data System (ADS)

    Juodawlkis, Paul William

    1999-11-01

    The large optical absorption and carrier-induced nonlinearities of semiconductor materials are useful for optical signal processing applications. For absorptive devices operating at ultrafast data rates (>100 Gb/s) or high optical intensities, it is necessary to reduce the intrinsic photo-excited carrier removal time. One method of achieving this reduction is to increase the nonradiative recombination rate through the controlled introduction of defects. In this thesis, we explore the use of low-temperature molecular-beam epitaxy (MBE) to introduce nonradiative recombination centers into InGaAs-based quantum-wells (QWs). The objectives of the thesis are: (i)to improve the understanding of the optoelectronic properties of low-temperature-grown (LTG) InGaAs/InAlAs QWs, and (ii)to assess the feasibility of using these materials for optical device applications in the 1.5-μm wavelength region. Time-resolved differential transmission measurements reveal that the nonlinear absorption recovery time in InGaAs/InAlAs QWs can be reduced from >100 ps to 0.6 ps through the combination of low-temperature growth (~250°C) and beryllium (Be) doping. The bandedge absorption slope and the nonlinear absorption cross- section are only diminished by factors of 2 to 3 relative to QWs grown at standard temperature (~500°C). The Be doping dependence of the recovery time and the residual electron density in the LTG-QWs can be mainly attributed to impurity-related compensation. Be doping also maintains the ultrafast recovery following thermal anneal. The recovery response results from fast electron- trapping followed by slow (>100 ps) trapped- electron/free-hole recombination. Detailed simulations of the nonlinear absorption saturation and recovery processes agree quantitatively with measured data and substantiate the importance of the photo-excitation wavelength on the observed recovery response. The absorption saturation model includes the competition between band-filling and band

  17. Optical properties of as-grown and annealed InAs quantum dots on InGaAs cross-hatch patterns

    PubMed Central

    2011-01-01

    InAs quantum dots (QDs) grown on InGaAs cross-hatch pattern (CHP) by molecular beam epitaxy are characterized by photoluminescence (PL) at 20 K. In contrast to QDs grown on flat GaAs substrates, those grown on CHPs exhibit rich optical features which comprise as many as five ground-state emissions from [1-10]- and [110]-aligned QDs, two wetting layers (WLs), and the CHP. When subject to in situ annealing at 700°C, the PL signals rapidly degrades due to the deterioration of the CHP which sets the upper limit of overgrowth temperature. Ex situ hydrogen annealing at a much lower temperature of 350°C, however, results in an overall PL intensity increase with a significant narrowing and a small blueshift of the high-energy WL emission due to hydrogen bonding which neutralizes defects and relieves associated strains. PMID:21849063

  18. Characterization of graphene grown on bulk and thin film nickel.

    PubMed

    Lu, Chun-Chieh; Jin, Chuanhong; Lin, Yung-Chang; Huang, Chi-Ruei; Suenaga, Kazu; Chiu, Po-Wen

    2011-11-15

    We report on graphene films grown by atmospheric pressure chemical vapor deposition on bulk and thin film nickel. Carbon precipitation on the polycrystalline grains is controlled by the methane concentration and substrate cooling rate. It is found that graphene grows over multiple grains, with edges terminating along the grain boundaries and with dimensions directly correlated to the size of the underlying grains. This greatly restricts the resulting graphene size (<10 μm) in the thin film growth, whereas monolayer graphene with linear dimensions of hundreds of micrometers takes up the great majority of the surface overlayers on the bulk nickel (>50%). In addition, the number of layers can be better controlled in the bulk growth. Characterizations of the graphene sheets using transmission electron microscopy, Raman spectroscopy, and transport measurements in the field-effect configuration are also discussed. PMID:21967558

  19. Terahertz radiation using log-spiral-based low-temperature-grown InGaAs photoconductive antenna pumped by mode-locked Yb-doped fiber laser.

    PubMed

    Kong, Moon Sik; Kim, Ji Su; Han, Sang Pil; Kim, Namje; Moon, Kiwon; Park, Kyung Hyun; Jeon, Min Yong

    2016-04-01

    We demonstrate a terahertz (THz) radiation using log-spiral-based low-temperature-grown (LTG) InGaAs photoconductive antenna (PCA) modules and a passively mode-locked 1030 nm Yb-doped fiber laser. The passively mode-locked Yb-doped fiber laser is easily implemented with nonlinear polarization rotation in the normal dispersion using a 10-nm spectral filter. The laser generates over 250 mW of the average output power with positively chirped 1.58 ps pulses, which are dechirped to 127 fs pulses using a pulse compressor outside the laser cavity. In order to obtain THz radiation, a home-made emitter and receiver constructed from log-spiral-based LTG InGaAs PCA modules were used to generate and detect THz signals, respectively. We successfully achieved absorption lines over 1.5 THz for water vapor in free space. Therefore, we confirm that a mode-locked Yb-doped fiber laser has the potential to be used as an optical source to generate THZ waves. PMID:27136997

  20. Comparison of luminescent efficiency of InGaAs quantum well structures grown on Si, GaAs, Ge, and SiGe virtual substrate

    NASA Astrophysics Data System (ADS)

    Yang, V. K.; Ting, S. M.; Groenert, M. E.; Bulsara, M. T.; Currie, M. T.; Leitz, C. W.; Fitzgerald, E. A.

    2003-05-01

    In order to study the luminescent efficiency of InGaAs quantum wells on Si via SiGe interlayers, identical In0.2Ga0.8As quantum well structures with GaAs and Al0.25Ga0.75As cladding layers were grown on several substrates by an atmospheric metalorganic vapor deposition system. The substrates used include GaAs, Si, Ge, and SiGe virtual substrates. The SiGe virtual substrates were graded from Si substrates to 100% Ge content. Because of the small lattice mismatch between GaAs and Ge (0.07%), high-quality GaAs-based thin films with threading dislocation densities <3×106 cm-2 were realized on these SiGe substrates. Quantitative cathodoluminescence was used to compare the luminescent efficiency of the quantum well structure on the different substrates and cross-sectional transmission electron microscopy was used to characterize dislocation densities. Our results show that the InGaAs quantum wells grown on the GaAs substrates have the highest luminescent efficiencies due to the lowest dislocation densities. Interestingly, InGaAs quantum wells grown on the SiGe virtual substrates outperform those on Ge substrates, both in terms of luminescent efficiency and dislocation density. This difference is attributed to the variation in thermal expansion coefficient (α) and its impact on defect structure during the process cycle. The SiGe virtual substrate has a smaller α compared to a Ge substrate because of the smaller α of the Si substrate, which helps minimize compressive strain in the quantum well layer during the temperature decrease from the growth temperature. Consequently, fewer misfit dislocations are created between the quantum well and cladding interfaces. These misfits can greatly affect the luminescent efficiency since they can act as recombination sites. In general, the efficiencies of the quantum wells on the SiGe and Ge substrates were affected only by higher misfit dislocation densities, whereas the quantum wells on the Si substrate had low efficiency due to

  1. Electron beam evaporated carbon doping of InGaAs layers grown by gas source molecular beam epitaxy

    SciTech Connect

    Salokatve, A.; Toivonen, M.; Asonen, H.; Pessa, M.; Likonen, J.

    1996-12-31

    The authors have studied carbon doping of GaInAs grown by gas-source molecular beam epitaxy. Graphite was used as a source material for carbon evaporation. GaInAs was studied due to its importance as a base layer in InP-based heterojunction bipolar transistors. They show that useful p-type acceptor concentrations can be achieved by evaporation from graphite source for GaInAs grown by gas-source molecular beam epitaxy. Secondary ion mass spectroscopy and Van der Pauw Hall measurements were used to characterize the carbon and net acceptor concentrations of their GaInAs layers. The effect of rapid thermal annealing on acceptor concentrations and Hall mobilities was also studied.

  2. Defect studies in 4H- Silicon Carbide PVT grown bulk crystals, CVD grown epilayers and devices

    NASA Astrophysics Data System (ADS)

    Byrappa, Shayan M.

    Silicon Carbide [SiC] which exists as more than 200 different polytypes is known for superior high temperature and high power applications in comparison to conventional semiconductor materials like Silicon and Germanium. The material finds plethora of applications in a diverse fields due to its unique properties like large energy bandgap, high thermal conductivity and high electric breakdown field. Though inundated with superior properties the potential of this material has not been utilized fully due to impeding factors such as defects especially the crystalline ones which limit their performance greatly. Lots of research has been going on for decades to reduce these defects and there has been subsequent improvement in the quality as the diameter of SiC commercial wafers has reached 150mm from 25mm since its inception. The main focus of this thesis has been to study yield limiting defect structures in conjunction with several leading companies and national labs using advanced characterization tools especially the Synchrotron source. The in depth analysis of SiC has led to development of strategies to reduce or eliminate the density of defects by studying how the defects nucleate, replicate and interact in the material. The strategies discussed to reduce defects were proposed after careful deliberation and analysis of PVT grown bulk crystals and CVD grown epilayers. Following are some of the results of the study: [1] Macrostep overgrowth mechanism in SiC was used to study the deflection of threading defects onto the basal plane resulting in stacking faults. Four types of stacking faults associated with deflection of c/c+a threading defects have been observed to be present in 76mm, 100mm and 150mm diameter wafers. The PVT grown bulk crystals and CVD grown epilayers in study were subjected to contrast studies using synchrotron white beam X-ray topography [SWBXT]. The SWBXT image contrast studies of these stacking faults with comparison of calculated phase shifts for

  3. Low defect InGaAs quantum well selectively grown by metal organic chemical vapor deposition on Si(100) 300 mm wafers for next generation non planar devices

    SciTech Connect

    Cipro, R.; Gorbenko, V.; Baron, T. Martin, M.; Moeyaert, J.; David, S.; Bassani, F.; Bogumilowicz, Y.; Barnes, J. P.; Rochat, N.; Loup, V.; Vizioz, C.; Allouti, N.; Chauvin, N.; Bao, X. Y.; Ye, Z.; Pin, J. B.; Sanchez, E.

    2014-06-30

    Metal organic chemical vapor deposition of GaAs, InGaAs, and AlGaAs on nominal 300 mm Si(100) at temperatures below 550 °C was studied using the selective aspect ratio trapping method. We clearly show that growing directly GaAs on a flat Si surface in a SiO{sub 2} cavity with an aspect ratio as low as 1.3 is efficient to completely annihilate the anti-phase boundary domains. InGaAs quantum wells were grown on a GaAs buffer and exhibit room temperature micro-photoluminescence. Cathodoluminescence reveals the presence of dark spots which could be associated with the presence of emerging dislocation in a direction parallel to the cavity. The InGaAs layers obtained with no antiphase boundaries are perfect candidates for being integrated as channels in n-type metal oxide semiconductor field effect transistor (MOSFET), while the low temperatures used allow the co-integration of p-type MOSFET.

  4. Carrier dynamics in bulk 1eV InGaAsNSb materials and epitaxial lift off GaAs-InAlGaP layers grown by MOVPE for multi-junction solar cells

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; LaLumondiere, Stephen; Lotshaw, William; Moss, Steven C.; Kim, Tae Wan; Forghani, Kamran; Mawst, Luke J.; Kuech, Thomas F.; Tatavarti, Rao; Wibowo, Andree; Pan, Noren

    2013-03-01

    III-V multi-junction solar cells are based on a triple-junction design that consists of an InGaP top junction, a GaAs middle junction, and a bottom junction that employs either a 1eV material grown on the GaAs substrate or InGaAs grown on the Ge substrate. The most promising 1 eV material that is currently under extensive investigation is bulk dilute nitride such as InGaAsN(Sb) lattice matched to GaAs substrates. Both approaches utilizing dilute nitrides and lattice-mismatched InGaAs layers have a potential to achieve high performance triple-junction solar cells. In addition, it will be beneficial for both commercial and space applications if III-V triple-junction solar cells can significantly reduce weight and can be manufactured cost effectively while maintaining high efficiency. The most attractive approach to achieve these goals is to employ full-wafer epitaxial lift off (ELO) technology, which can eliminate the substrate weight and also enable multiple substrate re-usages. For the present study, we employed time-resolved photoluminescence (TR-PL) techniques to study carrier dynamics in MOVPE-grown bulk dilute nitride layers lattice matched to GaAs substrates, where carrier lifetime measurements are crucial in optimizing MOVPE materials growth. We studied carrier dynamics in InGaAsN(Sb) layers with different amounts of N incorporated. Carrier lifetimes were also measured from InGaAsN(Sb) layers at different stages of post-growth thermal annealing steps. Post-growth annealing yielded significant improvements in carrier lifetimes of InGaAsNSb double hetero-structure (DH) samples compared to InGaAsN DH samples possibly due to the surfactant effect of Sb. In addition, we studied carrier dynamics in MOVPE-grown GaAs-InAl(Ga)P layers grown on GaAs substrates. The structures were grown on top of a thin AlAs release layer, which allowed epitaxial layers grown on top of the AlAs layer to be removed from the substrate. The GaAs layers had various doping densities and

  5. Surface studies of gallium nitride quantum dots grown using droplet epitaxy on bulk, native substrates

    NASA Astrophysics Data System (ADS)

    Jones, Christina; Jeon, Sunyeol; Goldman, Rachel; Yacoby, Yizhak; Clarke, Roy

    Gallium nitride (GaN) and its applications in light-emitting diodes play an integral part in efficient, solid-state lighting, as evidenced by its recognition in the 2014 Nobel prize in physics. In order to push this technology towards higher efficiency and reliability and lower cost, we must understand device growth on bulk GaN substrates, which have lower defect densities and strain than template GaN substrates grown on sapphire. In this work, we present our findings on the surface properties of GaN quantum dots (QDs) grown on commercial bulk GaN. QDs are grown using the droplet epitaxy method and analyzed using a surface X-ray diffraction technique called Coherent Bragg Rod Analysis (COBRA), which uses phase retrieval to reconstruct atomic positions near the substrate surface. While several QD growth conditions in our study produce dense QDs, COBRA reveals that only low nitridation temperatures result in GaN QDs that are coherent with the bulk GaN substrate. Results are supported with atomic force microscopy and high-resolution transmission electron microscopy.

  6. A comparative study of AlN and Al2O3 based gate stacks grown by atomic layer deposition on InGaAs

    NASA Astrophysics Data System (ADS)

    Krylov, Igor; Pokroy, Boaz; Ritter, Dan; Eizenberg, Moshe

    2016-02-01

    Thermal activated atomic layer deposited (t) (ALD) and plasma enhanced (p) ALD (PEALD) AlN films were investigated for gate applications of InGaAs based metal-insulator-semiconductor devices and compared to the well-known Al2O3 based system. The roles of post-metallization annealing (PMA) and the pre-deposition treatment (PDT) by either trimethylaluminium (TMA) or NH3 were studied. In contrast to the case of Al2O3, in the case of AlN, the annealing temperature reduced interface states density. In addition, improvement of the AlN film stoichiometry and a related border traps density reduction were observed following PMA. The lowest interface states density (among the investigated gate stacks) was found for PEALD AlN/InGaAs stacks after TMA PDT. At the same time, higher values of the dispersion in accumulation were observed for AlN/InGaAs gate stacks compared to those with Al2O3 dielectric. No indium out-diffusion and the related leakage current degradation due to annealing were observed at the AlN/InGaAs stack. In light of these findings, we conclude that AlN is a promising material for InGaAs based gate stack applications.

  7. Near-infrared electroluminescence and photo detection in InGaAs p-i-n microdisks grown by selective area growth on silicon

    NASA Astrophysics Data System (ADS)

    Kjellman, Jon Øyvind; Sugiyama, Masakazu; Nakano, Yoshiaki

    2014-06-01

    Microselective-area growth of p-i-n InGaAs disks on (111) silicon by metalorganic chemical vapor deposition is a promising technology for III/V-on-Si integration. As a proof-of-concept, room-temperature electroluminescence is reported from ensembles of p-i-n InGaAs-on-Si micro-disks. The observed spectrum shows peak luminescence at 1.78 μm with a local maxima at 1.65 μm. The disks are also shown to generate a measurable photo current when illuminated by infrared light with less energy than the silicon bandgap energy. This makes these InGaAs-on-Si disks a promising technology for monolithic integration of light sources and detectors with silicon photonics and complementary metal-oxide-semiconductor electronics for optical communication, sensing, and imaging.

  8. Electrical and structural characterization of as-grown and annealed hydrothermal bulk ZnO

    SciTech Connect

    Kassier, G. H.; Hayes, M.; Auret, F. D.; Mamor, M.; Bouziane, K.

    2007-07-01

    Hall effect measurements in the range 20-370 K on as-grown and annealed hydrothermal bulk ZnO have been performed. The bulk conductivity in the highly resistive as-grown sample was found to decrease and then increase after annealing at 550 deg. C and 930 deg. C, respectively. The conduction in the as-grown material is attributed to a deep donor which is replaced by a much shallower donor after annealing at 930 deg. C. Annealing at both temperatures also produced strong surface conduction effects. Nondegenerate low-mobility surface conduction dominated the electrical properties of the sample annealed at 550 deg. C, while a degenerate surface channel was formed after annealing at 930 deg. C. In addition, Rutherford backscattering and channeling spectrometry (RBS/C) was used to assess the effect of annealing on the crystalline quality of the samples. RBS/C measurements reveal that annealing at 930 deg. C leads to significant improvement of the crystalline quality of the material, while annealing at 550 deg. C results in the segregation of a nonchanneling impurity at the surface.

  9. Photoluminescence Studies of ZnSe Starting Materials and Vapor Grown Bulk Crystals

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, S.; Wang, Ling Jun; Lehoczky, S. L.

    2001-01-01

    Low-temperature photoluminescence (PL) spectra were measured on ZnSe starting materials provided by various vendors and on bulk crystals grown from these starting materials by physical vapor transport (PVT) to study the effects of purification and contamination during PVT process. The impurity levels in one set of starting material/grown crystal were also measured by glow discharge mass spectroscopy (GDMS). The purification effect of pre-growth heat treatments and the PVT process is evidenced from the GDMS results which showed orders of magnitude reduction in the Li and Na concentration and a factor of 3 reduction in the O content after growth. The PL spectra showed that the strong emissions associated with Li (or Na) in one of the starting materials disappeared after growth. The GDMS results also showed increases in the At and Si contents by orders of magnitude after growth. To evaluate the contamination of the crystal during the high temperature growth process, three growth runs were processed using similar growth parameters but different furnace environments. The PL spectra suggest that the At contamination originated from the fused silica ampoule and that the Inconel cartridge might have been the cause of the broad Cu green and Cu red bands observed in one of the grown crystals.

  10. Bottom-up and top-down fabrication of nanowire-based electronic devices: In situ doping of vapor liquid solid grown silicon nanowires and etch-dependent leakage current in InGaAs tunnel junctions

    NASA Astrophysics Data System (ADS)

    Kuo, Meng-Wei

    Semiconductor nanowires are important components in future nanoelectronic and optoelectronic device applications. These nanowires can be fabricated using either bottom-up or top-down methods. While bottom-up techniques can achieve higher aspect ratio at reduced dimension without having surface and sub-surface damage, uniform doping distributions with abrupt junction profiles are less challenging for top-down methods. In this dissertation, nanowires fabricated by both methods were systematically investigated to understand: (1) the in situ incorporation of boron (B) dopants in Si nanowires grown by the bottom-up vapor-liquid-solid (VLS) technique, and (2) the impact of plasma-induced etch damage on InGaAs p +-i-n+ nanowire junctions for tunnel field-effect transistors (TFETs) applications. In Chapter 2 and 3, the in situ incorporation of B in Si nanowires grown using silane (SiH4) or silicon tetrachloride (SiCl4) as the Si precursor and trimethylboron (TMB) as the p-type dopant source is investigated by I-V measurements of individual nanowires. The results from measurements using a global-back-gated test structure reveal nonuniform B doping profiles on nanowires grown from SiH4, which is due to simultaneous incorporation of B from nanowire surface and the catalyst during VLS growth. In contrast, a uniform B doping profile in both the axial and radial directions is achieved for TMBdoped Si nanowires grown using SiCl4 at high substrate temperatures. In Chapter 4, the I-V characteristics of wet- and dry-etched InGaAs p+-i-n+ junctions with different mesa geometries, orientations, and perimeter-to-area ratios are compared to evaluate the impact of the dry etch process on the junction leakage current properties. Different post-dry etch treatments, including wet etching and thermal annealing, are performed and the effectiveness of each is assessed by temperaturedependent I-V measurements. As compared to wet-etched control devices, dry-etched junctions have a significantly

  11. Photoluminescence Studies of ZnSe Starting Materials and Vapor Grown Bulk Crystals

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, Shari; Wang, Ling Jun; Lehoczky, Sandor L.

    1999-01-01

    Low-temperature photoluminescence (PL) spectra and glow discharge mass spectroscopy (GDMS) were measured on ZnSe starting materials provided by various vendors and on bulk crystals grown from these starting materials by physical vapor transport (PVT) to study the effects of purification and contamination during crystal growth process. The purification effect of pre-growth heat treatments and the PVT process is evidenced from the GDMS results which showed orders of magnitude reduction in the Li and Na concentration and a factor of 3 reduction in the 0 content after growth. The PL spectra showed that the strong emissions associated with Li (or Na) in one of the starting materials disappeared after growth. To evaluate the contamination of the crystal during the high temperature growth process three growth runs were processed using similar growth parameters but with different furnace environments. The GDMS results showed orders of magnitude increase in the Al and Si contents after growth. The PL spectra suggest that the Al contamination was originated from the fused silica ampoule and the Inconel cartridge might have been the cause for the broad Cu green and Cu red bands observed in one of the grown crystal.

  12. Lattice constant and hardness of InSb:Bi bulk crystals grown by vertical directional solidification

    NASA Astrophysics Data System (ADS)

    Maske, Dilip; Deshpande, Manisha; Choudhary, Rashmi; Gadkari, Dattatray

    2016-05-01

    Ingots of the Bi doped InSb (InSb1-xBix) bulk semiconductor crystals were grown by specially designed Vertical Directional Solidification (VDS) technique. Substrates of seven crystals grown with various composition values of x (0 ≤ x < 0.1) were used to analyze the effect of Bi incorporation on the crystal lattice, bonding energy and physical strength of the material. Lattice constant of each substrate was calculated using 2ɵ angles of the peak positions in the powder XRD. FTIR was used in its transmission mode to find the band edge and calculate the energy band gap. Reduction in the energy band was found up to 0.105 eV. The substrates were tested for their toughness using Vickers micro-hardness test. Comparison of these measurements with the corresponding values of undoped InSb indicate that, due to Bi incorporation in InSb lattice there is increase in the lattice constant (°A) and decrease in the energy band gap (eV) in the ratio 2:1, and decrease in the micro-hardness up to ˜20% for the Bi composition x > 0.05.

  13. Carrier dynamics in QW and bulk bismide and epitaxial lift off GaAs-In(Al)GaP double heterostructures grown by MOVPE for multi-junction solar cells

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Peterson, Mark; Lingley, Zachary; LaLumondiere, Stephen; Moss, Steven C.; Kim, Honghyuk; Forghani, Kamran; Guan, Yingxin; Kim, Kangho; Lee, Jaejin; Mawst, Luke J.; Kuech, Thomas F.; Tatavarti, Rao

    2016-03-01

    III-V multi-junction solar cells are based on a triple-junction design that consists of an InGaP top junction, a GaAs middle junction, and a bottom junction that employs either a 1eV material grown on the GaAs substrate or InGaAs grown on the Ge substrate. The most promising 1 eV materials under extensive investigation are the bulk dilute nitride such as InGaAsN(Sb) lattice-matched to GaAs substrate and the dilute-bismide quantum well materials, such as GaAsBi, strain-compensated with GaAsP barriers. Both approaches have the potential to achieve high performance triple-junction solar cells. In addition, space satellite applications utilizing III-V triple-junction solar cells can have significantly reduced weight and high efficiency. An attractive approach to achieve these goals is to employ full-wafer epitaxial lift off (ELO) technology, which can eliminate the substrate weight and also enable multiple substrate re-usages. For the present study, we employed time-resolved photoluminescence (TR-PL) techniques to study carrier dynamics in MOVPE-grown bulk dilute bismide double heterostructures (DH). Carrier lifetime measurements are crucial to optimizing MOVPE materials growth. We have studied carrier dynamics in GaAsBi QW structures with GaAsP barriers. Carrier lifetimes were measured from GaAsBi DH samples at different stages of post-growth thermal annealing steps. Post-growth annealing yielded significant improvements in carrier lifetimes. Based on this study, single junction solar cells (SJSC) were grown and annealed under a variety of conditions and characterized. The SJSC annealed at 600 - 650 °C exhibited improved response in EQE spectra. In addition, we studied carrier dynamics in MOVPE-grown GaAs-In(Al)GaP DH samples grown on GaAs substrates. The structures were grown on top of a thin AlAs release layer, which allowed epitaxial layers grown on top of the AlAs layer to be removed from the substrate. The GaAs active layers had various doping densities and

  14. Measurement of the extent of strain relief in InGaAs layers grown under tensile strain on InP(100) substrates

    NASA Astrophysics Data System (ADS)

    Maigné, P.; Gendry, M.; Venet, T.; Tahri, Y.; Hollinger, G.

    1996-07-01

    High resolution x-ray diffraction has been used to investigate the structural properties of InxGa1-xAs epitaxial layers grown under tension on InP(100) substrates. The nominal indium composition (x=0.42) corresponds to a small lattice mismatch and a two dimensional growth mode. We have also included for comparison two samples grown under compression covering the mostly strained and the mostly relaxed regimes. Our results show that the residual strain and the asymmetry in strain relaxation along <011> directions are always larger for layers under tension. This can be explained by the difference in dislocation glide velocity induced by a different indium content, by the dissociation of perfect dislocations and partially by the difference in thermal expansion coefficients between substrate and epilayer. The larger asymmetry in strain relaxation for tensile strain layers is interpreted by the existence of microcracks aligned in the [011] direction.

  15. Tilted bulk heterojunction organic photovoltaic cells grown by oblique angle deposition

    NASA Astrophysics Data System (ADS)

    Li, Ning; Forrest, Stephen R.

    2009-09-01

    We demonstrate small molecule bulk heterojunction organic photovoltaic cells using oblique angle vacuum deposition. Obliquely deposited donor chloroaluminum phthalocyanine (ClAlPc) films on indium tin oxide have surface feature sizes of ˜30 nm, resulting in ClAlPc/C60 donor-acceptor heterojunctions (HJs) with approximately twice the interface area of HJs grown at normal incidence. This results in nearly twice the external quantum efficiency in the ClAlPc absorption band compared with analogous, planar HJs. The efficiency increase is attributed to the increased surface area presented by the donor-acceptor junction to the incident illumination by ClAlPc protrusions lying obliquely to the substrate plane formed during deposition. The power conversion efficiency improves from (2.0±0.1)% to (2.8±0.1)% under 1 sun, AM 1.5G simulated solar illumination. Similarly, the power efficiency of copper phthalocyanine/C60 organic photovoltaic cells is increased from (1.3±0.1)% to (1.7±0.1)%.

  16. InGaAs Photodetectors Cut-off at 1.9 μm Grown by Gas-Source Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-Gang; Hao, Guo-Qiang; Gu, Yi; Zhu, Cheng; Li, Ai-Zhen; Liu, Tian-Dong

    2005-01-01

    Using a linear graded InxGa1-xAs as the buffer layer, positive-intrinsic-negative wavelength-extended In0.6Ga0.4 As photodetectors with 50% cut-off wavelength of 1.9 μm at room temperature were grown by using gas-source molecular beam epitaxy, and their performance over a wide temperature range has been extensively investigated. The detectors show typical dark current at bias voltage 50 mV and the resistance-area product R0A of 7 nA/765 Ωcm2 and 31 pA/404 kΩcm2 at 290 K and 210 K, respectively. The thermal activation energy of the dark current in the temperature range 250-350 K is 0.488 eV.

  17. Two-dimensional ordering of (In,Ga)As quantum dots in vertical multilayers grown on GaAs(100) and (n11)

    SciTech Connect

    Lytvyn, P. M.; Strelchuk, V. V.; Kolomys, O. F.; Prokopenko, I. V.; Valakh, M. Ya.; Mazur, Yu. I.; Wang, Zh. M.; Salamo, G. J.; Hanke, M.

    2007-10-22

    We have investigated lateral self-assembling in In{sub 0.4}Ga{sub 0.6}As/GaAs quantum dot (QD) multilayers, which were grown by molecular beam epitaxy on GaAs(100) and (n11)B substrates with n=9,8,7,5,4,3. The lateral self-assembling and the QD size distribution have been studied by atomic force microscopy depending on substrate orientation and the number of periods within the multilayers. The observed two-dimensional ordering can be described by a centered rectangular surface unit cell. Derived autocorrelation functions exhibit the most pronounced lateral QD assembling along the elastically soft directions [1n0]. This can be attributed to elastic interaction, the particular elastic anisotropy of the high index substrates, and the minimization of the strain energy.

  18. Initial stages of chain formation in a single layer of (In,Ga)As quantum dots grown on GaAs (100)

    SciTech Connect

    Schmidbauer, M.; Wang, Zh. M.; Mazur, Yu. I.; Lytvyn, P. M.; Salamo, G. J.; Grigoriev, D.; Schaefer, P.; Koehler, R.; Hanke, M.

    2007-08-27

    The self-organized formation of In{sub 0.40}Ga{sub 0.60}As quantum dot chains was investigated using x-ray scattering. Two samples were compared grown on GaAs(100) by molecular beam epitaxy. The first sample with a single layer of In{sub 0.40}Ga{sub 0.60}As dots shows weak quantum dot alignment and a corresponding elongated shape along [011], while the top layer of a multilayered In{sub 0.40}Ga{sub 0.60}As/GaAs sample exhibits extended and highly regular quantum dot chains oriented along [011]. Numerical calculations of the three-dimensional strain fields are used to explain the initial stages of chain formation by anisotropic strain relaxation induced by the elongated dot shape.

  19. Optical and mechanical studies on unidirectional grown tri-nitrophenol methyl p-hydroxybenzoate bulk single crystal

    NASA Astrophysics Data System (ADS)

    Uthrakumar, R.; Vesta, C.; Robert, R.; Mangalam, G.; Jerome Das, S.

    2010-10-01

    The bulk single crystal of tri-nitrophenol methyl p-hydroxybenzoate (TNMPHB) of length 90 mm and diameter 12 mm was obtained by employing unidirectional growth technique. Single crystal X-ray diffraction studies and powder XRD analysis have been carried out to confirm the identity of the crystal. The optical band gap of the grown crystal was calculated to be 4.91 eV from UV transmission spectrum. The mechanical strength of the grown crystal has been studied using Vicker's microhardness tester. Low dielectric loss shows that the grown crystal contains lesser defects authenticating the suitability of the crystal towards device applications. The surface morphology studies have been carried out on the grown crystal.

  20. Optical properties of InGaN grown by MOCVD on sapphire and on bulk GaN

    NASA Astrophysics Data System (ADS)

    Osinski, Marek; Eliseev, Petr G.; Lee, Jinhyun; Smagley, Vladimir A.; Sugahara, Tamoya; Sakai, Shiro

    1999-11-01

    Experimental data on photoluminescence of various bulk and quantum-well epitaxial InGaN/GaN structures grown by MOCVD are interpreted in terms of a band-tail model of inhomogeneously broadened radiative recombination. The anomalous temperature-induced blue spectral is shown to result from band-tail recombination under non-degenerate conditions. Significant differences are observed between epilayers grown on sapphire substrates and on GaN substrates prepared by the sublimination method, with no apparent evidence of band tails in homoepitaxial structures, indicating their higher crystalline quality.

  1. Influence of Mg and In on defect formation in GaN; bulk and MOCVD grown samples

    SciTech Connect

    Liliental-Weber, Z.; Benamara, M.; Jasinski, J.; Swider, W.; Washburn, J.; Grzegory, I.; Porowski, S.; Bak-Misiuk, J.; Domagala, J.; Bedair, S.; Eiting, C.J.; Dupuis, R.D.

    2000-11-22

    Transmission electron microscopy studies were applied to study GaN crystals doped with Mg. Both: bulk GaN:Mg crystals grown by a high pressure and high temperature process and those grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering (formation of polytypoids) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects with base on the basal planes and with walls inclined about 45O to these planes, empty inside (pinholes) were observed. A high concentration of these pyramidal defects was also observed in the MOCVD grown crystals. For samples grown with Mg delta doping planar defects were also observed especially at the early stages of growth followed by formation of pyramidal defects. TEM and x-ray studies of InxGa{sub 1{minus}x}N crystals for the range of 28-45% nominal In concentration shows formation of two sub-layers: strained and relaxed, with a much lower In concentration in the strained layer. Layers with the highest In concentration were fully relaxed.

  2. Time-resolved PL and TEM studies of MOVPE-grown bulk dilute nitride and bismide quantum well heterostructure

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Lingley, Zachary; Peterson, Mark; Brodie, Miles; Moss, Steven C.; Kim, Tae Wan; Kim, Honghyuk; Guan, Yingxin; Forghani, K.; Mawst, Luke J.; Kuech, Thomas F.

    2015-03-01

    Among several approaches proposed to achieve high-efficiency III-V multi-junction solar cells, the most promising approach is to incorporate a bottom junction consisting of a 1 - 1.25 eV material. In particular, several research groups have studied MBE- and MOVPE-grown 1 - 1.25 eV bulk (In)GaAsN(Sb) dilute nitride lattice matched to GaAs substrates, but it is a challenge to grow dilute nitrides without introducing a number of localized states or defects. Localized states originating from random distributions of nitrogen sites in dilute nitrides behave as highly efficient traps, leading to short minority carrier lifetimes. As our group previously reported, carrier dynamics studies are indispensable in the optimization of dilute nitride materials growth to achieve improved solar cell performance. Also, bismide QW heterostructures have recently received a great deal of attention for applications in solar cells and semiconductor lasers because theoretical studies have predicted reduction in nonradiative recombination in Bicontaining materials. For the present study, we employed time-resolved photoluminescence (TR-PL) techniques to study carrier dynamics in MOVPE-grown bulk (In)GaAsN(Sb) materials nominally lattice matched to GaAs substrates. Compared to our previous samples, our present samples grown using different metalorganic precursors at higher growth temperatures showed a significantly less background C doping density. Carrier lifetimes were measured from such dilute nitride samples with low C doping density at various temperatures between 10K and RT. We also performed preliminary TR-PL measurements on MOVPE-grown bismide QW heterostructures at low temperatures. Carrier lifetimes were measured from as-grown and annealed bismide QW structures consisting of GaAsBi(P) wells and GaAsP barriers. Lastly, TEM cross sections were prepared from both dilute nitride and bismide samples for defect and composition analysis using a high resolution TEM.

  3. Grown-in defects limiting the bulk lifetime of p-type float-zone silicon wafers

    NASA Astrophysics Data System (ADS)

    Grant, N. E.; Rougieux, F. E.; Macdonald, D.; Bullock, J.; Wan, Y.

    2015-02-01

    We investigate a recombination active grown-in defect limiting the bulk lifetime (τbulk) of high quality float-zone (FZ) p-type silicon wafers. After annealing the samples at temperatures between 80 °C and 400 °C, τbulk was found to increase from ˜500 μs to ˜1.5 ms. By isochronal annealing the p-type samples between 80 °C and 400 °C for 30 min, the annihilation energy (Eann) of the defect was determined to be 0.3 < Eann < 0.7 eV. When the annihilated samples were phosphorus gettered at 880 °C or subject to 0.2 sun illumination for 24 h, τbulk was found to degrade. However, when the samples were subsequently annealed at temperatures between 250 and 400 °C, the defect could be re-annihilated. The experimental results suggest that the defect limiting the lifetime in the p-type FZ silicon is not related to fast diffusing metallic impurities but rather to a lattice-impurity or an impurity-impurity metastable defect.

  4. Radiation-induced defects in GaN bulk grown by halide vapor phase epitaxy

    SciTech Connect

    Duc, Tran Thien; Pozina, Galia; Son, Nguyen Tien; Janzén, Erik; Hemmingsson, Carl; Ohshima, Takeshi

    2014-09-08

    Defects induced by electron irradiation in thick free-standing GaN layers grown by halide vapor phase epitaxy were studied by deep level transient spectroscopy. In as-grown materials, six electron traps, labeled D2 (E{sub C}–0.24 eV), D3 (E{sub C}–0.60 eV), D4 (E{sub C}–0.69 eV), D5 (E{sub C}–0.96 eV), D7 (E{sub C}–1.19 eV), and D8, were observed. After 2 MeV electron irradiation at a fluence of 1 × 10{sup 14 }cm{sup −2}, three deep electron traps, labeled D1 (E{sub C}–0.12 eV), D5I (E{sub C}–0.89 eV), and D6 (E{sub C}–1.14 eV), were detected. The trap D1 has previously been reported and considered as being related to the nitrogen vacancy. From the annealing behavior and a high introduction rate, the D5I and D6 centers are suggested to be related to primary intrinsic defects.

  5. Radiation-induced defects in GaN bulk grown by halide vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Duc, Tran Thien; Pozina, Galia; Son, Nguyen Tien; Janzén, Erik; Ohshima, Takeshi; Hemmingsson, Carl

    2014-09-01

    Defects induced by electron irradiation in thick free-standing GaN layers grown by halide vapor phase epitaxy were studied by deep level transient spectroscopy. In as-grown materials, six electron traps, labeled D2 (EC-0.24 eV), D3 (EC-0.60 eV), D4 (EC-0.69 eV), D5 (EC-0.96 eV), D7 (EC-1.19 eV), and D8, were observed. After 2 MeV electron irradiation at a fluence of 1 × 1014 cm-2, three deep electron traps, labeled D1 (EC-0.12 eV), D5I (EC-0.89 eV), and D6 (EC-1.14 eV), were detected. The trap D1 has previously been reported and considered as being related to the nitrogen vacancy. From the annealing behavior and a high introduction rate, the D5I and D6 centers are suggested to be related to primary intrinsic defects.

  6. Characterization of bulk hexagonal boron nitride single crystals grown by the metal flux technique

    NASA Astrophysics Data System (ADS)

    Edgar, J. H.; Hoffman, T. B.; Clubine, B.; Currie, M.; Du, X. Z.; Lin, J. Y.; Jiang, H. X.

    2014-10-01

    The optical and physical properties of hexagonal boron nitride single crystals grown from a molten metal solution are reported. The hBN crystals were grown by precipitation from a nickel-chromium flux with a boron nitride source, by slowly cooling from 1500 °C at 2-4 °C/h under a nitrogen flow at atmospheric pressure. The hBN crystals formed on the surface of the flux with an apparent crystal size up to 1-2 mm in diameter. Individual grains were as large as 100-200 μm across. Typically, the flakes removed from the metal were 6-20 μm thick. Optical absorption measurements suggest a bandgap of 5.8 eV by neglecting the binding energy of excitons in hBN. The highest energy photoluminescence peak was at 5.75 eV at room temperature. The hBN crystals typically had a pit density of 5×106 cm-2 after etching in a molten eutectic mixture of potassium hydroxide and sodium hydroxide. The quality of these crystals suggests they are suitable as substrates for two dimensional materials such as graphene and gallium nitride based devices.

  7. Intrinsically tunable bulk acoustic wave resonators based on sol-gel grown PMN-PT films

    NASA Astrophysics Data System (ADS)

    Vorobiev, A.; Spreitzer, M.; Veber, A.; Suvorov, D.; Gevorgian, S.

    2014-08-01

    Intrinsically tunable bulk acoustic wave resonators, based on sol-gel 0.70Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMN-PT) thin films, with high effective electromechanical coupling coefficient of 13% and tunability of the series resonance frequency up to 4.0% are fabricated and characterized. The enhanced electroacoustic properties of the PMN-PT resonators are attributed to the mechanism of polarization rotation occurring in the region of the morphotropic phase boundary. Electroacoustic performance of the PMN-PT resonators is analyzed using the theory of dc field-induced piezoelectric effect in ferroelectrics. Extrinsic acoustic loss in the PMN-PT resonators is analyzed using the model of the wave scattering at reflections from rough interfaces. Mechanical Q-factor of the resonators is up to 70 at 4.1 GHz and limited mainly by losses in the PMN-PT film.

  8. Comparison between structural properties of bulk GaN grown under high N pressure and GaN grown by other methods

    SciTech Connect

    Liliental-Weber, Z.; Jasinski, J.; Washburn, J.

    2002-07-31

    In this paper defects formed in GaN grown by different methods are reviewed. Formation of particular defects are often related to the crystallographic direction in which the crystals grow. For bulk crystals the highest growth rates are observed for directions perpendicular to the c-axis. Threading dislocations and nanopipes along the c-axis are not formed in these crystals, but polarity of the growth direction plays a role concerning defects that are formed and surface roughness. For growth of homoepitaxial layers, where growth is forced to take place in the c-direction threading dislocations are formed and their density is related to the purity of constituents used for growth and to substrate surface inhomogeneities. In heteroepitaxial layers two other factors: lattice mismatch and thermal expansion mismatch are related to the formation of dislocations. Doping of crystals can also lead to formation of defects characteristic for a specific dopant. This type of defects tends to be growth method independent but can depend on growth polarity.

  9. Comparison between structural properties of bulk GaN grown in liquid Ga under high N pressure and GaN grown by other methods

    NASA Astrophysics Data System (ADS)

    Liliental-Weber, Z.; Jasinski, J.; Washburn, J.

    2002-12-01

    In this paper defects formed in GaN grown by different methods are reviewed. Formation of particular defects are often related to the crystallographic direction in which the crystals grow. For bulk crystals the highest growth rates are observed for directions perpendicular to the c-axis. Threading dislocations and nanopipes along the c-axis are not formed in these crystals, but polarity of the growth direction plays a role concerning defects that are formed and surface roughness. For growth of homoepitaxial layers, where growth is forced to take place in the c-direction threading dislocations are formed and their density is related to the purity of constituents used for growth and to substrate surface inhomogeneities. In heteroepitaxial layers two other factors: lattice mismatch and thermal expansion mismatch are related to the formation of dislocations. Doping of crystals can also lead to the formation of defects characteristic for a specific dopant. This type of defects tends to be growth method independent but can depend on growth polarity.

  10. On the bulk β-Ga2O3 single crystals grown by the Czochralski method

    NASA Astrophysics Data System (ADS)

    Galazka, Zbigniew; Irmscher, Klaus; Uecker, Reinhard; Bertram, Rainer; Pietsch, Mike; Kwasniewski, Albert; Naumann, Martin; Schulz, Tobias; Schewski, Robert; Klimm, Detlef; Bickermann, Matthias

    2014-10-01

    The growth of bulkx β-Ga2O3 single crystals by the Czochralski method is reported and discussed in terms of crucial growth conditions and correlated with basic electrical and optical properties of the obtained crystals. β-Ga2O3 crystals have a tendency to a spiral formation due to free carrier absorption in the near infrared (NIR) wavelength range, which hampers radiative heat transfer through the growing crystal. Moderate or low free electron concentrations (<5×1017 cm-3) lead to cylindrical crystals with a high crystallized fraction (g≥0.5). The use of a CO2-containing growth atmosphere provides oxygen partial pressures between 0.8 and 4.4×10-2 bar that is sufficient to obtain cylindrical and semiconducting crystals. Doping with Sn increases the free electron concentration in the crystals to high values (~1019 cm-3) that lead to an immediate spiral formation, while doping with Mg (>6 wt ppm) provides insulating crystals with reduced probability of the spiral formation. The estimated Mg equilibrium segregation coefficient across the liquid-solid interface is 0.10-0.12. Annealing of undoped crystals in an oxidizing atmosphere at temperatures ≥1200 °C for 20 h decreases the bulk free electron concentration by about one order of magnitude, while the crystal surface becomes insulating. However, Mg:β-Ga2O3 crystals are insensitive to annealing in both oxygen- and hydrogen-containing atmospheres. The transmittance spectra showed a steep absorption edge at 260 nm and virtually full transparency in the visible and NIR wavelength range for low and moderate free electron concentrations. We also demonstrated the possibility of growing 2 in. diameter β-Ga2O3 single crystals by the Czochralski method. The good crystal quality is evidenced by rocking curve FWHM values of below 50". We noted that most dislocations propagate parallel to (100) plane. Further, we also provide thermal properties of the crystals as a function of temperature.

  11. Dielectric function of InGaAs in the visible

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Sieg, R. E.; Yao, H. D.; Snyder, P. G.; Woollam, J. A.; Pamulapati, J.; Bhattacharya, P. K.; Sekula-Moise, P. A.

    1990-01-01

    Measurements are reported of the dielectric function of thermodynamically stable In(x)Ga(1-x)As in the composition range 0.3 equal to or less than X = to or less than 0.7. The optically thick samples of InGaAs were made by molecular beam epitaxy (MBE) in the range 0.4 = to or less than X = to or less than 0.7 and by metal-organic chemical vapor deposition (MOCVD) for X = 0.3. The MBE made samples, usually 1 micron thick, were grown on semi-insulating InP and included a strain release structure. The MOCVD sample was grown on GaAs and was 2 microns thick. The dielectric functions were measured by variable angle spectroscopic ellipsometry in the range 1.55 to 4.4 eV. The data was analyzed assuming an optically thick InGaAs material with an oxide layer on top. The thickness of this layer was estimated by comparing the results for the InP lattice matched material, i.e., X = 0.53, with results published in the literature. The top oxide layer mathematically for X = 0.3 and X = 0.53 was removed to get the dielectric function of the bare InGaAs. In addition, the dielectric function of GaAs in vacuum, after a protective arsenic layer was removed. The dielectric functions for X = 0, 0.3, and 0.53 together with the X = 1 result from the literature to evaluate an algorithm for calculating the dielectric function of InGaAs for an arbitrary value of X(0 = to or less than X = to or less than 1) were used. Results of the dielectric function calculated using the algorithm were compared with experimental data.

  12. Dielectric function of InGaAs in the visible

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Yao, H. D.; Snyder, P. G.; Woolam, J. A.; Pamulapati, J.; Bhattacharya, P. K.; Sekula-Moise, P. A.; Sieg, R. E.

    1990-01-01

    Measurements are reported of the dielectric function of thermodynamically stable In(x)Ga(1-x)As in the composition range 0.3 equal to or less than X = to or less than 0.7. The optically thick samples of InGaAs were made by molecular beam epitaxy (MBE) in the range 0.4 = to or less than X = to or less than 0.7 and by metal-organic chemical vapor deposition (MOCVD) for X = 0.3. The MBE made samples, usually 1 micron thick, were grown on semi-insulating InP and included a strain release structure. The MOCVD sample was grown on GaAs and was 2 microns thick. The dielectric functions were measured by variable angle spectroscopic ellipsometry in the range 1.55 to 4.4 eV. The data was analyzed assuming an optically thick InGaAs material with an oxide layer on top. The thickness of this layer was estimated by comparing the results for the InP lattice matched material, i.e., X = 0.53, with results published in the literature. The top oxide layer mathematically for X = 0.3 and X = 0.53 was removed to get the dielectric function of the bare InGaAs. In addition, the dielectric function of GaAs in vacuum, after a protective arsenic layer was removed. The dielectric functions for X = 0, 0.3, and 0.53 together with the X = 1 result from the literature to evaluate an algorithm for calculating the dielectric function of InGaAs for an arbitrary value of X (0 = to or less than X = to or less than 1) were used. Results of the dielectric function calculated using the algorithm were compared with experimental data.

  13. Impact of thermal annealing on bulk InGaAsSbN materials grown by metalorganic vapor phase epitaxy

    SciTech Connect

    Kim, T. W.; Mawst, L. J.; Kim, K.; Lee, J. J.; Kuech, T. F.; Wells, N. P.; LaLumondiere, S. D.; Sin, Y.; Lotshaw, W. T.; Moss, S. C.

    2014-02-03

    Two different thermal annealing techniques (rapid thermal annealing (RTA) and in-situ post-growth annealing in the metalorganic vapor phase epitaxy (MOVPE) chamber) were employed to investigate their impact on the optical characteristics of double-heterostructures (DH) of InGaAsSbN/GaAs and on the performance of single-junction solar cell structures, all grown by MOVPE. We find that an optimized RTA procedure leads to a similar improvement in the photoluminescence (PL) intensity compared with material employing a multi-step optimized anneal within the MOVPE reactor. Time-resolved photoluminescence techniques at low temperature (LT) and room temperature (RT) were performed to characterize the carrier dynamics in bulk InGaAsSbN layers. Room temperature carrier lifetimes were found to be similar for both annealing methods, although the LT-PL (16 K) measurements of the MOVPE-annealed sample found longer lifetimes than the RTA-annealed sample (680 ps vs. 260 ps) for the PL measurement energy of 1.24 eV. InGaAsSbN-based single junction solar cells processed with the optimized RTA procedure exhibited an enhancement of the electrical performance, such as improvements in open circuit voltage, short circuit current, fill factor, and efficiency over solar cells subjected to the in-situ MOVPE annealing technique.

  14. Impact of thermal annealing on bulk InGaAsSbN materials grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Kim, T. W.; Kim, K.; Lee, J. J.; Kuech, T. F.; Mawst, L. J.; Wells, N. P.; LaLumondiere, S. D.; Sin, Y.; Lotshaw, W. T.; Moss, S. C.

    2014-02-01

    Two different thermal annealing techniques (rapid thermal annealing (RTA) and in-situ post-growth annealing in the metalorganic vapor phase epitaxy (MOVPE) chamber) were employed to investigate their impact on the optical characteristics of double-heterostructures (DH) of InGaAsSbN/GaAs and on the performance of single-junction solar cell structures, all grown by MOVPE. We find that an optimized RTA procedure leads to a similar improvement in the photoluminescence (PL) intensity compared with material employing a multi-step optimized anneal within the MOVPE reactor. Time-resolved photoluminescence techniques at low temperature (LT) and room temperature (RT) were performed to characterize the carrier dynamics in bulk InGaAsSbN layers. Room temperature carrier lifetimes were found to be similar for both annealing methods, although the LT-PL (16 K) measurements of the MOVPE-annealed sample found longer lifetimes than the RTA-annealed sample (680 ps vs. 260 ps) for the PL measurement energy of 1.24 eV. InGaAsSbN-based single junction solar cells processed with the optimized RTA procedure exhibited an enhancement of the electrical performance, such as improvements in open circuit voltage, short circuit current, fill factor, and efficiency over solar cells subjected to the in-situ MOVPE annealing technique.

  15. Optical properties of C-doped bulk GaN wafers grown by halide vapor phase epitaxy

    SciTech Connect

    Khromov, S.; Hemmingsson, C.; Monemar, B.; Hultman, L.; Pozina, G.

    2014-12-14

    Freestanding bulk C-doped GaN wafers grown by halide vapor phase epitaxy are studied by optical spectroscopy and electron microscopy. Significant changes of the near band gap (NBG) emission as well as an enhancement of yellow luminescence have been found with increasing C doping from 5 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3}. Cathodoluminescence mapping reveals hexagonal domain structures (pits) with high oxygen concentrations formed during the growth. NBG emission within the pits even at high C concentration is dominated by a rather broad line at ∼3.47 eV typical for n-type GaN. In the area without pits, quenching of the donor bound exciton (DBE) spectrum at moderate C doping levels of 1–2 × 10{sup 17} cm{sup −3} is observed along with the appearance of two acceptor bound exciton lines typical for Mg-doped GaN. The DBE ionization due to local electric fields in compensated GaN may explain the transformation of the NBG emission.

  16. Comparison of different grading schemes in InGaAs metamorphic buffers on GaAs substrate: Tilt dependence on cross-hatch irregularities

    NASA Astrophysics Data System (ADS)

    Kumar, Rahul; Bag, Ankush; Mukhopadhyay, Partha; Das, Subhashis; Biswas, Dhrubes

    2015-12-01

    InGaAs graded metamorphic buffers (MBs) with different grading strategies have been grown by molecular beam epitaxy (MBE) on GaAs (0 0 1) substrate. A detailed comparative analysis of surface using atomic force microscopy (AFM), and bulk properties using high resolution X-ray diffraction (HRXRD) and room temperature photoluminescence (RTPL) of grown MBs have been presented to comprehend the effectiveness of different grading scheme on InGaAs MBs. Conventional, statistical and fractal analysis on measured AFM data has been performed for in-depth investigation of these surfaces. The grading scheme has been found to have little impact on residual strain while it affects the epitaxial tilt significantly. Moreover, the tilt has been found to depend on growth front irregularities. Tilt magnitude in a graded MB has been found to vary with composition while tilt azimuth has been found to be almost same in the graded layers. PL Intensity and a shift in the PL peaks have been used to study the quality of the MB and residual strain comparatively.

  17. Multijunction InGaAs thermophotovoltaic power converter

    NASA Technical Reports Server (NTRS)

    Wojtczuk, Steven

    1996-01-01

    The experimental performance of a multijunction monolithic lattice-matched 0.74 eV InGaAs thermophotovoltaic (TPV) power converter under 980 C blackbody irradiation is reported. Eight InGaAs PN junctions grown epitaxially on a semi-insulating wafer were monolithically integrated in series to boost the approximately 0.4 V photovoltage per typical InGaAs junction to over 3 volts for the 1 cm(exp 2) chip. This chip was originally designed and characterized for free-space 1.3 micron laser power beaming. The power efficiency of this TPV device is 16% for that part of the blackbody spectrum above the material bandgap. The device is shown to deliver about 1 watt of output power when driven with enough light. This is the first report of such a multijunction TPV device. This is not a traditional tandem cell in which the junctions are stacked vertically. Eight 1 mm long by 1 cm wide junctions are laterally connected across the device area. This multijunction design has the potential for lower I(exp 2)R power loss since the smaller PN junction area limits the current to one eighth that of the equivalent surface area. In essence, the current is traded for voltage to avoid the I(exp 2)R loss, analogous to the way power utilities avoid I(exp 2)R loss in high-tension power lines, by transforming the high current, low voltage generated at a power plant into a high voltage at a low current before transmitting the power over great distances.

  18. A combined kick-out and dissociative diffusion mechanism of grown-in Be in InGaAs and InGaAsP. A new finite difference-Bairstow method for solution of the diffusion equations

    SciTech Connect

    Koumetz, Serge D. Martin, Patrick; Murray, Hugues

    2014-09-14

    Experimental results on the diffusion of grown-in beryllium (Be) in indium gallium arsenide (In{sub 0.53}Ga{sub 0.47}As) and indium gallium arsenide phosphide (In{sub 0.73}Ga{sub 0.27}As{sub 0.58}P{sub 0.42}) gas source molecular beam epitaxy alloys lattice-matched to indium phosphide (InP) can be successfully explained in terms of a combined kick-out and dissociative diffusion mechanism, involving neutral Be interstitials (Be{sub i}{sup 0}), singly positively charged gallium (Ga), indium (In) self-interstitials (I{sub III}{sup +}) and singly positively charged Ga, In vacancies (V{sub III}{sup +}). A new numerical method of solution to the system of diffusion equations, based on the finite difference approximations and Bairstow's method, is proposed.

  19. Variable temperature carrier dynamics in bulk (In)GaAsNSb materials grown by MOVPE for multi-junction solar cells

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Lingley, Zachary; LaLumondiere, Stephen; Wells, Nathan; Lotshaw, William; Moss, Steven C.; Kim, Tae Wan; Mawst, Luke J.; Kuech, Thomas F.

    2014-03-01

    III-V multi-junction solar cells are typically based on a triple-junction design that consists of an InGaP top junction, a GaAs middle junction, and a bottom junction that employs a 1 - 1.25 eV material grown on GaAs substrates. The most promising 1 - 1.25 eV material that is currently under extensive investigation is bulk dilute nitride such as (In)GaAsNSb lattice matched to GaAs substrates. The approach utilizing dilute nitrides has a great potential to achieve high performance triple-junction solar cells as recently demonstrated by Wiemer, et al., who achieved a record efficiency of 43.5% from multi-junction solar cells including MBE-grown dilute nitride materials [1]. Although MOVPE is a preferred technique over MBE for III-V multi-junction solar cell manufacturing, MOVPEgrown dilute nitride research is at its infancy compared to MBE-grown dilute nitride. In particular, carrier dynamics studies are indispensible in the optimization of MOVPE materials growth parameters to obtain improved solar cell performance. For the present study, we employed time-resolved photoluminescence (TR-PL) techniques to study carrier dynamics in MOVPE-grown bulk dilute nitride InGaAsN materials (Eg = 1 - 1.25 eV at RT) lattice matched to GaAs substrates. In contrast to our earlier samples that showed high background C doping densities, our current samples grown using different metalorganic precursors at higher growth temperatures showed a significantly reduced background doping density of ~ 1017 /cm3. We studied carrier dynamics in (In)GaAsNSb double heterostructures (DH) with different N compositions at room temperature. Post-growth annealing yielded significant improvements in carrier lifetimes of (In)GaAsNSb double heterostructure (DH) samples. Carrier dynamics at various temperatures between 10 K and RT were also studied from (In)GaAsNSb DH samples including those samples grown on different orientation substrates.

  20. The Thermoelectric Properties of Rare Earths as Dopants in InGaAs Films

    NASA Astrophysics Data System (ADS)

    Koltun, Rachel Ann

    Current energy technologies lose over half of the energy input to waste heat. Thermoelectric materials can recover some of this waste heat by converting it into electricity. Thermoelectric devices have no moving parts, so they are low noise and highly reliable, making them particularly suitable for extreme environments. A good thermoelectric has low thermal conductivity to maintain large temperature gradients and high electrical conductivity to effectively transport carriers across that temperature gradient. One of the major challenges in engineering such thermoelectrics is effectively decoupling these parameters. These relationships are quantified in the dimensionless thermoelectric figure of merit, ZT, where a ZT of 1 is considered commercially viable. Doping MBE grown InGaAs films with rare earths forms embedded nanoparticles that have been shown to improve thermoelectric efficiency of InGaAs. Rare earth doping effectively overcomes the problematic relationship between electrical and thermal conductivities. These embedded particles effectively decouple thermal and electrical properties by contributing carriers to increase electrical conductivity as well as forming scattering centers for mid to long wavelength phonons to decrease thermal conductivity. However, the mechanism for carrier generation from rare earths is poorly understood. Comparing different rare earths as dopants in InGaAs, we find a positive correlation with the electrical activation efficiency as the rare earth arsenide nanoparticles are more closely lattice matched to the host matrix. This is in contrast to traditional Si doped InGaAs, which is fully ionized at room temperature. The high doping efficiency of Si leads it to be as good or better of a dopant for thermoelectrics compared to the best rare earths studied. We observe that rare earth doped InGaAs has thermal activation of carriers at high temperature, giving it the potential to be a more efficient thermoelectric in this regime than

  1. Multijunction InGaAs thermophotovoltaic power converter

    SciTech Connect

    Wojtczuk, S.; Parodos, T.

    1995-10-01

    The experimental performance of a multijunction monolithic In(0.53)Ga(0.47)As power converter under blackbody irradiation is reported. Eight InGaAs PN junctions grown epitaxially on a semi-insulating wafer were monolithically integrated in series to boost the approximately 0.4 V photovoltage per typical InGaAs junction to over 3 volts for the 1 sq cm chip. This chip was originally designed and characterized for free-space 1.3 micron laser power beaming. This is the first report of such a multijunction TPV. This is not a traditional tandem cell in which the junctions are stacked vertically. The junctions are each about 1mm long by 1 cm wide and are laterally connected across the 1 sq cm device area. This multijunction design has the potential for lower I(sup 2)R power loss since the smaller PN junction area limits the current to one-eighth that of the equivalent surface area. In essence, the current is traded for voltage to avoid the I(sup 2)R loss, analogous to the way power utilities avoid I(sup 2)R loss in high-tension power lines, by transforming the high current, low voltage generated at a power plant into a high voltage at a low current before transmitting the power over great distances.

  2. Multijunction InGaAs thermophotovoltaic power converter

    NASA Technical Reports Server (NTRS)

    Wojtczuk, Steven; Parodos, Themis

    1995-01-01

    The experimental performance of a multijunction monolithic In(0.53)Ga(0. 47)As power converter under blackbody irradiation is reported. Eight InGaAs PN junctions grown epitaxially on a semi-insulating wafer were monolithically integrated in series to boost the approximately 0.4 V photovoltage per typical InGaAs junction to over 3 volts for the 1 sq cm chip. This chip was originally designed and characterized for free-space 1.3 micron laser power beaming. This is the first report of such a multijunction TPV. This is not a traditional tandem cell in which the junctions are stacked vertically. The junctions are each about 1mm long by 1 cm wide and are laterally connected across the 1 sq cm device area. This multijunction design has the potential for lower I(sup 2)R power loss since the smaller PN junction area limits the current to one-eighth that of the equivalent surface area. In essence, the current is traded for voltage to avoid the I(sup 2)R loss, analogous to the way power utilities avoid I(sup 2)P loss in high-tension power lines, by transforming the high current, low voltage generated at a power plant into a high voltage at a low current before transmitting the power over great distances.

  3. Stimulated emission and optical gain in AlGaN heterostructures grown on bulk AlN substrates

    SciTech Connect

    Guo, Wei Bryan, Zachary; Kirste, Ronny; Bryan, Isaac; Hussey, Lindsay; Bobea, Milena; Haidet, Brian; Collazo, Ramón; Sitar, Zlatko; Xie, Jinqiao; Mita, Seiji; Gerhold, Michael

    2014-03-14

    Optical gain spectra for ∼250 nm stimulated emission were compared in three different AlGaN-based structures grown on single crystalline AlN substrates: a single AlGaN film, a double heterostructure (DH), and a Multiple Quantum Well (MQW) structure; respective threshold pumping power densities of 700, 250, and 150 kW/cm{sup 2} were observed. Above threshold, the emission was transverse-electric polarized and as narrow as 1.8 nm without a cavity. The DH and MQW structures showed gain values of 50–60 cm{sup −1} when pumped at 1 MW/cm{sup 2}. The results demonstrated the excellent optical quality of the AlGaN-based heterostructures grown on AlN substrates and their potential for realizing electrically pumped sub-280 nm laser diodes.

  4. Three-dimensional whispering gallery modes in InGaAs nanoneedle lasers on silicon

    SciTech Connect

    Tran, T.-T. D.; Chen, R.; Ng, K. W.; Ko, W. S.; Lu, F.; Chang-Hasnain, C. J.

    2014-09-15

    As-grown InGaAs nanoneedle lasers, synthesized at complementary metal–oxide–semiconductor compatible temperatures on polycrystalline and crystalline silicon substrates, were studied in photoluminescence experiments. Radiation patterns of three-dimensional whispering gallery modes were observed upon optically pumping the needles above the lasing threshold. Using the radiation patterns as well as finite-difference-time-domain simulations and polarization measurements, all modal numbers of the three-dimensional whispering gallery modes could be identified.

  5. Ellipsometric study of InGaAs MODFET material

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Sieg, R. E.; Yao, H. D.; Snyder, P. G.; Woollam, J. A.; Pamulapati, J.; Bhattacharya, P. K.

    1990-01-01

    In(x)Ga(1-x)As based MODFET (modulation doped field effect transistor) material was grown by molecular beam epitaxy on semi-insulating InP substrates. Several structures were made, including lattice matched and strained layer InGaAs. All structures also included several layers of In(0.52)Al(0.48)As. Variable angle spectroscopic ellipsometry was used to characterize the structures. The experimental data, together with the calibration function for the constituent materials, were analyzed to yield the thickness of all the layers of the MODFET structure. Results of the ellipsometrically determined thicknesses compare very well with the reflection high energy electron diffraction in situ thickness measurements.

  6. Characterization and chemical surface texturization of bulk ZnTe crystals grown by temperature gradient solution growth

    NASA Astrophysics Data System (ADS)

    Yang, Rui; Jie, Wan-qi; Liu, Hang

    2015-07-01

    Using tellurium as a solvent, we grew ZnTe ingots of 30 mm in diameter and 70 mm in length by a temperature gradient solution growth method. Hall tests conducted at 300 K indicated that the as-grown ZnTe exhibits p-type conductivity, with a carrier concentration of approximately 1014 cm-3, a mobility of approximately 300 cm2·V-1·s-1, and a resistivity of approximately 102 Ω·cm. A simple and effective method was proposed for chemical surface texturization of ZnTe using an HF:H2O2:H2O etchant. Textures with the sizes of approximately 1 µm were produced on {100}, {110}, and {111}Zn surfaces after etching. The etchant is also very promising in crystal characterization because of its strong anisotropic character and Te-phase selectivity.

  7. Water absorption in thermally grown oxides on SiC and Si: Bulk oxide and interface properties

    SciTech Connect

    Liu, Gang; Xu, Can; Feldman, Leonard C.; Yakshinskiy, Boris; Wielunski, Leszek; Gustafsson, Torgny; Bloch, Joseph; Dhar, Sarit

    2014-11-10

    We combine nuclear reaction analysis and electrical measurements to study the effect of water exposure (D{sub 2}O) on the n-type 4H-SiC carbon face (0001{sup ¯}) MOS system and to compare to standard silicon based structures. We find that: (1) The bulk of the oxides on Si and SiC behave essentially the same with respect to deuterium accumulation; (2) there is a significant difference in accumulation of deuterium at the semiconductor/dielectric interface, the SiC C-face structure absorbs an order of magnitude more D than pure Si; (3) standard interface passivation schemes such as NO annealing greatly reduce the interfacial D accumulation; and (4) the effective interfacial charge after D{sub 2}O exposure is proportional to the total D amount at the interface.

  8. Optical properties of yellow light-emitting diodes grown on semipolar (112xAF2) bulk GaN substrates

    NASA Astrophysics Data System (ADS)

    Sato, Hitoshi; Chung, Roy B.; Hirasawa, Hirohiko; Fellows, Natalie; Masui, Hisashi; Wu, Feng; Saito, Makoto; Fujito, Kenji; Speck, James S.; DenBaars, Steven P.; Nakamura, Shuji

    2008-06-01

    We demonstrate high power yellow InGaN single-quantum-well light-emitting diodes (LEDs) with a peak emission wavelength of 562.7nm grown on low extended defect density semipolar (112¯2) bulk GaN substrates by metal organic chemical vapor deposition. The output power and external quantum efficiency at drive currents of 20 and 200mA under pulsed operation (10% duty cycle) were 5.9mW, 13.4% and 29.2mW, 6.4%, respectively. It was observed that the temperature dependence of the output power of InGaN LEDs was significantly smaller than that of AlInGaP LEDs.

  9. Interface Shape and Growth Rate Analysis of Se/GaAs Bulk Crystals Grown in the NASA Crystal Growth Furnace (CGF)

    NASA Technical Reports Server (NTRS)

    Bly, J. M.; Kaforey, M. L.; Matthiesen, D. H.; Chait, A.

    1997-01-01

    Selenium-doped gallium arsenide, Se/GaAs, bulk crystals have been grown on earth using NASA's crystal growth furnace (CGF) in preparation for microgravity experimentation on the USML-2 spacelab mission. Peltier cooling pulses of 50 ms duration, 2040 A magnitude, and 0.0033 Hz frequency were used to successfully demark the melt-solid interface at known times during the crystal growth process. Post-growth characterization included interface shape measurement, growth rate calculation, and growth rate transient determinations. It was found that the interface shapes were always slightly concave into the solid. The curvature of the seeding interfaces was typically 1.5 mm for the 15 mm diameter samples. This was in agreement with the predicted interface shapes and positions relative to the furnace determined using a numerical model of the sample/ampoule/cartridge assembly (SACA).

  10. High internal quantum efficiency in AlGaN multiple quantum wells grown on bulk AlN substrates

    SciTech Connect

    Bryan, Zachary Bryan, Isaac; Sitar, Zlatko; Collazo, Ramón; Xie, Jinqiao; Mita, Seiji

    2015-04-06

    The internal quantum efficiency (IQE) of Al{sub 0.55}Ga{sub 0.45}N/AlN and Al{sub 0.55}Ga{sub 0.45}N/Al{sub 0.85}Ga{sub 0.15}N UVC MQW structures was analyzed. The use of bulk AlN substrates enabled us to undoubtedly distinguish the effect of growth conditions, such as V/III ratio, on the optical quality of AlGaN based MQWs from the influence of dislocations. At a high V/III ratio, a record high IQE of ∼80% at a carrier density of 10{sup 18 }cm{sup −3} was achieved at ∼258 nm. The high IQE was correlated with the decrease of the non-radiative coefficient A and a reduction of midgap defect luminescence, all suggesting that, in addition to dislocations, point defects are another major factor that strongly influences optical quality of AlGaN MQW structures.

  11. Determination of CdTe bulk carrier lifetime and interface recombination velocity of CdTe/MgCdTe double heterostructures grown by molecular beam epitaxy

    SciTech Connect

    Zhao, Xin-Hao; Campbell, Calli M.; DiNezza, Michael J.; Liu, Shi; Zhao, Yuan; Zhang, Yong-Hang

    2014-12-22

    The bulk Shockley-Read-Hall carrier lifetime of CdTe and interface recombination velocity at the CdTe/Mg{sub 0.24}Cd{sub 0.76}Te heterointerface are estimated to be around 0.5 μs and (4.7 ± 0.4) × 10{sup 2 }cm/s, respectively, using time-resolved photoluminescence (PL) measurements. Four CdTe/MgCdTe double heterostructures (DHs) with varying CdTe layer thicknesses were grown on nearly lattice-matched InSb (001) substrates using molecular beam epitaxy. The longest lifetime of 179 ns is observed in the DH with a 2 μm thick CdTe layer. It is also shown that the photon recycling effect has a strong influence on the bulk radiative lifetime, and the reabsorption process affects the measured PL spectrum shape and intensity.

  12. Photoluminescence characteristics of ZnTe bulk crystal and ZnTe epilayer grown on GaAs substrate by MOVPE

    NASA Astrophysics Data System (ADS)

    Lü, Hai-Yan; Mu, Qi; Zhang, Lei; Lü, Yuan-Jie; Ji, Zi-Wu; Feng, Zhi-Hong; Xu, Xian-Gang; Guo, Qi-Xin

    2015-12-01

    Excitation power and temperature-dependent photoluminescence (PL) spectra of the ZnTe epilayer grown on (100) GaAs substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the GaAs substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor-acceptor pair (DAP) nor conduction band-acceptor (e-A) emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120131110006), the Key Science and Technology Program of Shandong Province, China (Grant No. 2013GGX10221), the Key Laboratory of Functional Crystal Materials and Device (Shandong University, Ministry of Education), China (Grant No. JG1401), the National Natural Science Foundation of China (Grant No. 61306113), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91433112), and the Partnership Project for Fundamental Technology Researches of the Ministry of Education, Culture, Sports, Science and Technology, Japan.

  13. Thermophotovoltaic energy converters based on thin film selective emitters and InGaAs photovoltaic cells

    SciTech Connect

    Fatemi, N.S.; Hoffman, R.H.; Wilt, D.M.; Lowe, R.A.; Garverick, L.M.; Scheiman, D.

    1996-02-01

    This paper presents the results of an investigation to demonstrate thermophotovoltaic energy conversion using InGaAs photovoltaic cells, yttrium-aluminum-garnet- (YAG-) based selective emitters, and bandpass/reflector filters, with the heat source operating at 1100{degree}C. InGaAs cells were grown on InP by organometallic vapor phase epitaxy with bandgaps of 0.60 and 0.75 eV and coupled to Ho-, Er-, and Er-Tm-doped YAG selective emitters. Infrared reflector and/or shortpass filters were also used to increase the ratio of in-band to out-of-band radiation from the selective emitters. Efficiencies as high as 13.2{percent} were recorded for filtered converters. {copyright} {ital 1996 American Institute of Physics.}

  14. Border trap reduction in Al2O3/InGaAs gate stacks

    NASA Astrophysics Data System (ADS)

    Tang, Kechao; Winter, Roy; Zhang, Liangliang; Droopad, Ravi; Eizenberg, Moshe; McIntyre, Paul C.

    2015-11-01

    The effect of Al2O3 atomic layer deposition (ALD) temperature on the border trap density (Nbt) of Al2O3/InGaAs gate stacks is investigated quantitatively, and we demonstrate that lowering the trimethylaluminum (TMA)/water vapor ALD temperature from 270 °C to 120 °C significantly reduces Nbt. The reduction of Nbt coincides with increased hydrogen incorporation in low temperature ALD-grown Al2O3 films during post-gate metal forming gas annealing. It is also found that large-dose (˜6000 L) exposure of the In0.53Ga0.47As (100) surface to TMA immediately after thermal desorption of a protective As2 capping layer is an important step to guarantee the uniformity and reproducibility of high quality Al2O3/InGaAs samples made at low ALD temperatures.

  15. Crystal growth of compound semiconductors in a low-gravity environment (InGaAs crystals) (M-22)

    NASA Technical Reports Server (NTRS)

    Tatsumi, Masami

    1993-01-01

    Compound semiconductor crystals, such as gallium arsenide and indium phosphide crystals, have many interesting properties that silicon crystals lack, and they are expected to be used as materials for optic and/or electro-optic integrated devices. Generally speaking, alloy semiconductors, which consist of more than three elements, demonstrate new functions. For example, values of important parameters, such as lattice constant and emission wavelength, can be chosen independently. However, as it is easy for macroscopic and/or microscopic fluctuations of composition to occur in alloy semiconductor crystals, it is difficult to obtain crystals having homogeneous properties. Macroscopic change of composition in a crystal is caused by the segregation phenomenon. This phenomenon is due to a continuous change in the concentration of constituent elements at the solid-liquid interfacing during solidification. On Earth, attempts were made to obtain a crystal with homogeneous composition by maintaining a constant melt composition near the solid-liquid interface, through suppression of the convection flow of the melt by applying a magnetic field. However, the attempt was not completely successful. Convective flow does not occur in microgravity because the gravity in space is from four to six orders of magnitude less than that on Earth. In such a case, mass transfer in the melt is dominated by the diffusion phenomenon. So, if crystal growth is carried out at a rate that is higher than the rate of mass transfer due to this phenomenon, it is expected that crystals having a homogeneous composition will be obtained. In addition, it is also possible that microscopic composition fluctuations (striation) may disappear because microscopic fluctuations diminish in the absence of convection. We are going to grow a bulk-indium gallium arsenide (InGaAs) crystal using the gradient heating furnace (GHF) in the first material processing test (FMPT). The structure of the sample is shown where InGaAs

  16. Characteristics and reliability of high power multi-mode InGaAs strained quantum well single emitters with CW output powers of over 5W

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Presser, Nathan; Mason, Maribeth; Moss, Steven C.

    2006-02-01

    High-power multi-mode broad area InGaAs strained quantum well (QW) single emitters (λ ~ 920-980nm) have been mainly used for industrial applications. Recently, these broad area lasers with CW output powers >5W have also found applications in communications as pump lasers for Er-Yb co-doped fiber amplifiers. This application requires very demanding characteristics including higher reliability than industrial applications. In contrast to 980nm single mode InGaAs strained QW lasers that are widely employed in both terrestrial and submarine applications, the fact that multimode lasers have never been used in optical communications necessitates careful study of these lasers. We report investigations of performance characteristics, reliability, and failure modes of high-power multi-mode single emitters. The lasers studied were broad area strained InGaAs-GaAs single QW lasers grown either by MOCVD or MBE. Typical apertures were around 100μm wide and cavity lengths were <=4.2mm. AR-HR coated laser diode chips were mounted on carriers with junction down configuration to reduce thermal impedance. Laser thresholds were <=453mA at RT. At 6A injection current typical CW output powers were over 5W at 25°C with wall-plug efficiency of ~60%. Characteristics measured included thermal impedance and optical beam profiles that are critical in understanding performance and reliability. Automatic current control burn-in tests with different stress conditions were performed and log (I)-V characteristics were measured at RT to correlate degradation in optical output power and an increase in trap density estimated from the 2κ•T term in bulk recombination current. We also report initial analysis of lifetest results and failure modes from these lasers.

  17. Thermal carrier emission and nonradiative recombinations in nonpolar (Al,Ga)N/GaN quantum wells grown on bulk GaN

    SciTech Connect

    Corfdir, P.; Dussaigne, A.; Giraud, E.; Ganiere, J.-D.; Grandjean, N.; Deveaud-Pledran, B.; Teisseyre, H.; Suski, T.; Grzegory, I.; Lefebvre, P.

    2012-02-01

    We investigate, via time-resolved photoluminescence, the temperature-dependence of charge carrier recombination mechanisms in nonpolar (Al,Ga)N/GaN single quantum wells (QWs) grown via molecular beam epitaxy on the a-facet of bulk GaN crystals. We study the influence of both QW width and barrier Al content on the dynamics of excitons in the 10-320 K range. We first show that the effective lifetime of QW excitons {tau} increases with temperature, which is evidence that nonradiative mechanisms do not play any significant role in the low-temperature range. The temperature range for increasing {tau} depends on the QW width and Al content in the (Al,Ga)N barriers. For higher temperatures, we observe a reduction in the QW emission lifetime combined with an increase in the decay time for excitons in the barriers, until both exciton populations get fully thermalized. Based on analysis of the ratio between barrier and QW emission intensities, we demonstrate that the main mechanism limiting the radiative efficiency in our set of samples is related to nonradiative recombination in the (Al,Ga)N barriers of charge carriers that have been thermally emitted from the QWs.

  18. Effect of Cr/In-doping on the crystalline quality of bulk ZnTe crystals grown from Te solution by temperature gradient solution growth (TGSG) method

    NASA Astrophysics Data System (ADS)

    Rui, Yang; Wanqi, Jie; Xiaoyan, Sun; Min, Yang

    2015-09-01

    The properties of undoped, Cr-doped, and In-doped bulk ZnTe crystals grown by the TGSG method were compared. Cr/In-doping leads to a slight red-shift of the absorption edge. Cr-doping also creates two characteristic absorption bands, centered at about 1750 nm and beneath the fundamental absorption edge. However, the fundamental reflectance spectra are not sensitive to the dopants. The resistivity of undoped, Cr-doped, and In-doped ZnTe is about 102 Ω·cm, 103 Ω·cm, and 108 Ω·cm, respectively. Only In-doped ZnTe has an IR transmittance higher than 60% in the range of 500 to 4000 cm-1. However, the IR transmittance of Cr-doped ZnTe is very low and decreases greatly as the wavenumber increases, which is mainly attributed to the scattering effects caused by some defects generated by Cr-doping. Project supported by the National Basic Research Program of China (No. 2011CB610406), the National Natural Science Foundation of China (No. 51372205), the 111 Project of China (No. B08040), the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20116102120014), and the NWPU Foundation for Fundamental Research and the Research Fund of the State Key Laboratory of Solidification Processing (NWPU).

  19. Microstructural dependency of optical properties of m-plane InGaN multiple quantum wells grown on 2° misoriented bulk GaN substrates

    SciTech Connect

    Tang, Fengzai; Barnard, Jonathan S.; Zhu, Tongtong; Oehler, Fabrice; Kappers, Menno J.; Oliver, Rachel A.

    2015-08-24

    A non-polar m-plane structure consisting of five InGaN/GaN quantum wells (QWs) was grown on ammonothermal bulk GaN by metal-organic vapor phase epitaxy. Surface step bunches propagating through the QW stack were found to accommodate the 2° substrate miscut towards the -c direction. Both large steps with heights of a few tens of nanometres and small steps between one and a few atomic layers in height are observed, the former of which exhibit cathodoluminescence at longer wavelengths than the adjacent m-plane terraces. This is attributed to the formation of semi-polar facets at the steps on which the QWs are shown to be thicker and have higher Indium contents than those in the adjacent m-plane regions. Discrete basal-plane stacking faults (BSFs) were occasionally initiated from the QWs on the main m-plane terraces, but groups of BSFs were frequently observed to initiate from those on the large steps, probably related to the increased strain associated with the locally higher indium content and thickness.

  20. Microstructural dependency of optical properties of m-plane InGaN multiple quantum wells grown on 2° misoriented bulk GaN substrates

    NASA Astrophysics Data System (ADS)

    Tang, Fengzai; Barnard, Jonathan S.; Zhu, Tongtong; Oehler, Fabrice; Kappers, Menno J.; Oliver, Rachel A.

    2015-08-01

    A non-polar m-plane structure consisting of five InGaN/GaN quantum wells (QWs) was grown on ammonothermal bulk GaN by metal-organic vapor phase epitaxy. Surface step bunches propagating through the QW stack were found to accommodate the 2° substrate miscut towards the -c direction. Both large steps with heights of a few tens of nanometres and small steps between one and a few atomic layers in height are observed, the former of which exhibit cathodoluminescence at longer wavelengths than the adjacent m-plane terraces. This is attributed to the formation of semi-polar facets at the steps on which the QWs are shown to be thicker and have higher Indium contents than those in the adjacent m-plane regions. Discrete basal-plane stacking faults (BSFs) were occasionally initiated from the QWs on the main m-plane terraces, but groups of BSFs were frequently observed to initiate from those on the large steps, probably related to the increased strain associated with the locally higher indium content and thickness.

  1. The effect of nucleation layer thickness on the structural evolution and crystal quality of bulk GaN grown by a two-step process on cone-patterned sapphire substrate

    NASA Astrophysics Data System (ADS)

    Shang, Lin; Zhai, Guangmei; Mei, Fuhong; Jia, Wei; Yu, Chunyan; Liu, Xuguang; Xu, Bingshe

    2016-05-01

    The role of nucleation layer thickness on the GaN crystal quality grown on cone-patterned sapphire substrate (PSS) was explored. The morphologies of epitaxial GaN at different growth stages were investigated by a series of growth interruption in detail. After 10- and 15-min three-dimensional growth, the nucleation sites are very important for the bulk GaN crystal quality. They have a close relationship with the nucleation layer thickness, as confirmed through the scanning electron microscope (SEM) analysis. Nucleation sites formed mainly on patterns are bad for bulk GaN crystal quality and nucleation sites formed mainly in the trenches of PSS mounds are good for bulk GaN crystal quality, as proved by X-ray diffraction analysis. Nucleation layer thickness can effectively control the nucleation sites and thus determine the crystal quality of bulk GaN.

  2. The temperature dependent variation of bulk and surface composition of In(x)Ga(1-x)As on GaAs grown by chemical beam epitaxy studied by RHEED, X-ray diffraction and XPS

    NASA Technical Reports Server (NTRS)

    Hansen, H. S.; Bensaoula, A.; Tougaard, S.; Zborowski, J.; Ignatiev, A.

    1992-01-01

    The paper investigates the bulk as well as near-surface composition of In(x)Ga(1-x)As epilayers on GaAs grown by chemical beam epitaxy (CBE) as a function of triethylindium flow rate and substrate temperature by reflection high energy electron diffraction (RHEED), X-ray diffraction, and XPS. To clarify whether the bulk stoichiometry of CBE-grown ternaries can be extracted from the growth rate change as determined by the change in the period of RHEED oscillations from binary to ternary compound growth, a systematic study of growth rate change as a function of ternary bulk composition determined by X-ray diffraction was performed at various temperatures. It is shown that for low growth temperatures there is a linear relationship between the two methods of determination, whereas no correlation is found for higher growth temperatures, in contrast to the MBE case where the two methods of determination yield identical results. In the near surface region the epilayer composition is determined in situ by XPS.

  3. Highly c-axis oriented growth of GaN film on sapphire (0001) by laser molecular beam epitaxy using HVPE grown GaN bulk target

    SciTech Connect

    Kushvaha, S. S.; Kumar, M. Senthil; Maurya, K. K.; Dalai, M. K.; Sharma, Nita D.

    2013-09-15

    Growth temperature dependant surface morphology and crystalline properties of the epitaxial GaN layers grown on pre-nitridated sapphire (0001) substrates by laser molecular beam epitaxy (LMBE) were investigated in the range of 500–750 °C. The grown GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM), micro-Raman spectroscopy, and secondary ion mass spectroscopy (SIMS). The x-ray rocking curve full width at a half maximum (FWHM) value for (0002) reflection dramatically decreased from 1582 arc sec to 153 arc sec when the growth temperature was increased from 500 °C to 600 °C and the value further decreased with increase of growth temperature up to 720 °C. A highly c-axis oriented GaN epitaxial film was obtained at 720 °C with a (0002) plane rocking curve FWHM value as low as 102 arc sec. From AFM studies, it is observed that the GaN grain size also increased with increasing growth temperature and flat, large lateral grains of size 200-300 nm was obtained for the film grown at 720 °C. The micro-Raman spectroscopy studies also exhibited the high-quality wurtzite nature of GaN film grown on sapphire at 720 °C. The SIMS measurements revealed a non-traceable amount of background oxygen impurity in the grown GaN films. The results show that the growth temperature strongly influences the surface morphology and crystalline quality of the epitaxial GaN films on sapphire grown by LMBE.

  4. 15 μm pixel-pitch VGA InGaAs module for very low background applications

    NASA Astrophysics Data System (ADS)

    Rouvié, A.; Huet, O.; Reverchon, J. L.; Robo, J. A.; Truffer, J. P.; Decobert, J.; Costard, E.; Bois, P.

    2011-11-01

    Thanks to the high transmission coefficient of short infrared wavelengths in the atmosphere and specific contrasts, SWIR imaging is an attractive technology for space applications such as astronomical or earth observation. Detection module must demonstrate high uniformity, sensitivity and resolution combined with compactness to meet the needs of this application field. Image sensors based on InGaAs photodiodes arrays present very low dark currents even at ambient temperature as high quality materials can be grown on InP substrates. Besides, the suppression of InP substrate after hybridization is a way to extend the detection range towards visible wavelengths. These properties result in a new generation of sensitive, compact and multifunctional InGaAs detection modules. In this paper, we describe the performances of an uncooled VGA InGaAs module recently developed. The 640x512 array with a pitch of 15μm allows high resolution images. The excellent crystalline quality induces very low dark current densities at ambient temperature. The readout circuit is based on a capacitive trans-impedance amplifier with correlated double sampling resulting in low readout noise figure. This compact module appears as a serious alternative to the existing technologies for low light level imaging in the [0.4μm-1.7μm] spectral range.

  5. Ground-state energy trends in single and multilayered coupled InAs/GaAs quantum dots capped with InGaAs layers: Effects of InGaAs layer thickness and annealing temperature

    SciTech Connect

    Shah, S.; Ghosh, K.; Jejurikar, S.; Mishra, A.; Chakrabarti, S.

    2013-08-01

    Graphical abstract: - Highlights: • Investigation of ground state energy in single and multi-layered InAs/GaAs QD. • Strain reducing layer (InGaAs) prevents the formation of non-radiative. • Strain reducing layer (InGaAs) is responsible for high activation energy. • Significant deviation from the Varshni model, E(T) = E − αT{sup 2}/T + β. - Abstract: Vertically coupled, multilayered InAs/GaAs quantum dots (QDs) covered with thin InGaAs strain-reducing layers (SRLs) are in demand for various technological applications. We investigated low temperature photoluminescence of single and multilayered structures in which the SRL thickness was varied. The SRL layer was responsible for high activation energies. Deviation of experimental data from the Varshni (1967) model, E(T) = E − ∞ T{sup 2}/T + β, suggests that the InAs-layered QDs have properties different from those in bulk material. Anomalous ground-state peak linewidths (FWHM), especially for annealed multilayer structures, were observed. A ground-state peak blue-shift with a broadened linewidth was also observed. Loss of intensity was detected in samples annealed at 800 °C. Presence of SRLs prevents formation of non-radiative centers under high temperature annealing. The results indicate the potential importance of such structures in optoelectronic applications.

  6. Location of Trapped Electron Centers in the Bulk of Epitaxial MgO(001) Films Grown on Mo(001) Using in situ W -band Electron Paramagnetic Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cornu, Damien; Rocker, Jan; Gonchar, Anastasia; Risse, Thomas; Freund, Hans-Joachim

    2016-07-01

    We present the first in situ W -band (94-GHz) electron paramagnetic resonance (EPR) study of a trapped electron center in thin MgO(001) films. The improved resolution of the high-field EPR experiments proves that the signal originate from a well-defined species present in the bulk of the films, whose projection of the principal g -tensor components onto the (001) plane are oriented along the [110] direction of the MgO lattice. Based on a comparison between the structural properties of the films, knowledge of the ability of bulk defects to trap electrons, and the properties of the EPR signal, it is possible to propose that the paramagnetic species are located at the origin of a screw dislocation in the bulk of the film.

  7. Wurtzite ZnO (001) films grown on cubic MgO (001) with bulk-like opto-electronic properties

    SciTech Connect

    Zhou Hua; Wang Huiqiong; Chen Xiaohang; Zhan Huahan; Kang Junyong; Wu Lijun; Zhu Yimei; Zhang Lihua; Kisslinger, Kim

    2011-10-03

    We report the growth of ZnO (001) wurtzite thin films with bulk-like opto-electronic properties on MgO (001) cubic substrates using plasma-assisted molecular beam epitaxy. In situ reflection high-energy electron diffraction patterns and ex situ high resolution transmission electron microscopy images indicate that the structure transition from the cubic MgO substrates to the hexagonal films involves 6 ZnO variants that have the same structure but different orientations. This work demonstrates the possibility of integrating wurtzite ZnO films and functional cubic substrates while maintaining their bulk-like properties.

  8. Multijunction InGaAs thermophotovoltaic devices

    SciTech Connect

    Fatemi, N.S.; Jenkins, P.P.; Weizer, V.G.; Wilt, D.M.; Murray, C.S.

    1998-12-31

    A monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the radiator for recuperation, thereby providing for high system efficiencies. MIMs were fabricated with an active area of 0.9 {times} 1 cm, and with 15 cells monolithically connected in series. Both lattice-matched and lattice-mismatched InGaAs/InP devices were fabricated, with bandgaps of 0.74 and 0.55 eV, respectively. The 0.74 eV MIMs demonstrated an open-circuit voltage (Voc) of 6.16 V and a fill factor of 74.2% at a short-circuit current (Jsc) of 0.84 A/cm{sup 2}, under flashlamp testing. The 0.55 eV MIMs demonstrated a Voc of 4.85 V and a fill factor of 57.8% at a Jsc of 3.87 A/cm{sup 2}. Electrical performance results for these MIMs are presented.

  9. SWIR InGaAs focal plane arrays in France

    NASA Astrophysics Data System (ADS)

    Rouvié, A.; Huet, O.; Hamard, S.; Truffer, J. P.; Pozzi, M.; Decobert, J.; Costard, E.; Zécri, M.; Maillart, P.; Reibel, Y.; Pécheur, A.

    2013-06-01

    SWIR detection band benefits from natural (sun, night glow, thermal radiation) or artificial (eye safe lasers) photons sources combined to low atmospheric absorption and specific contrast compared to visible wavelengths. It gives the opportunity to address a large spectrum of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control). InGaAs material appears as a good candidate to satisfy SWIR detection needs. The lattice matching with InP constitutes a double advantage to this material: attractive production capacity and uncooled operation thanks to low dark current level induced by high quality material. The study of InGaAs FPA has begun few years ago with III-VLab, gathering expertise in InGaAs material growth and imaging technology respectively from Alcatel-Lucent and Thales, its two mother companies. This work has led to put quickly on the market a 320x256 InGaAs module. The recent transfer of imagery activities from III-VLab to Sofradir allows developing new high performances products, satisfying customers' new requirements. Especially, a 640x512 InGaAs module with a pitch of 15µm is actually under development to fill the needs of low light level imaging.

  10. InGaAs focal plane array developments and perspectives

    NASA Astrophysics Data System (ADS)

    Rouvié, A.; Coussement, Jérome; Huet, O.; Truffer, JP.; Pozzi, Maxime; Oubensaid, E. H.; Hamard, S.; Maillart, P.; Costard, E.

    2014-10-01

    Thanks to the various developments presently available, SWIR technology presents a growing interest and gives the opportunity to address a large spectrum of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control). InGaAs material, initially developed for telecommunications detectors, appears as a good candidate to satisfy SWIR detection needs. The lattice matching with InP constitutes a double advantage to this material: attractive production capacity and uncooled operation thanks to low dark current level induced by high quality material. In the context of this evolving domain, the InGaAs imagery activities from III-VLab were transferred to Sofradir, which provides a framework for the production activity with the manufacturing of high performances products: CACTUS320 and CACTUS640. The developments towards VGA format with 15μm pixel pitch, lead today to the industrialization of a new product: SNAKE SW. On one side, the InGaAs detection array presents high performances in terms of dark current and quantum efficiency. On the other side, the low noise ROIC has different additional functionalities. Then this 640x512 @ 15μm module appears as well suited to answer the needs of a wide range of applications. In this paper, we will present the Sofradir InGaAs technology, the performances of our last product SNAKE SW and the perspectives of InGaAs new developments.

  11. The fabrication process of a high performance and pure c-axis grown GdBCO bulk superconductor with the TSMT-IG technique

    NASA Astrophysics Data System (ADS)

    Wang, Miao; Yang, Peng-tao; Yang, Wan-min; Li, Jia-wei; Hassan, Qadeer UI

    2015-10-01

    It is very important to choose a suitable seed crystal in the fabrication process of the (RE)BCO bulk superconductors by the top-seeded growth method, because a defective seed would result in the failure of the entire sample. Therefore, for optimizing the seed, a new approach is proposed in this paper for the fabrication process of Gd-Ba-Cu-O (GdBCO) bulk with promising superconducting properties. We developed the top-seeded melt texture and infiltration growth (TSMT-IG) process based on the modified top-seeded infiltration and growth (TSIG) process. In this modified infiltration growth, a mini pellet of thin melting texture (TMT) GdBCO was inserted between the NdBCO seed crystal and the solid-phase precursor pellet, resulting in the successful formation of well purified c-axis-oriented GdBCO crystals with a proper-sized TMT layer. The growth morphology, microstructure, side growth boundary, and superconducting properties of the GdBCO bulk superconductors with three different sizes of TMT pellets were studied in this paper. The results proved that the success rate for the fabrication of single-domain GdBCO bulk superconductors can be improved by the TSMT-IG process, which can also effectively inhibit the random nucleation phenomenon at some extent during the process of single-domain GdBCO bulk superconductor growth. In addition, the application of this new growth technology can help us not only to improve the growth performance of GdBCO samples with a proper size of the TMT mini pellet but also reduce the fabrication cost due to the use of only one precursor powder.

  12. Coupling of single InGaAs quantum dots to the plasmon resonance of a metal nanocrystal

    SciTech Connect

    Urbanczyk, A.; Hamhuis, G. J.; Noetzel, R.

    2010-07-26

    The authors report the coupling of single InGaAs quantum dots (QDs) to the surface plasmon resonance of a metal nanocrystal. Clear enhancement of the photoluminescence (PL) in the spectral region of the surface plasmon resonance is observed which splits up into distinct emission lines from single QDs in micro-PL. The hybrid metal-semiconductor structure is grown by molecular beam epitaxy on GaAs (100) utilizing the concept of self-organized anisotropic strain engineering for realizing ordered arrays with nanometer-scale precise positioning of the metal nanocrystals with respect to the QDs.

  13. Influence of crystallization front direction on the Mg-related impurity centers incorporation in bulk GaN:Mg grown by HNPS method

    NASA Astrophysics Data System (ADS)

    Sadovyi, B.; Amilusik, M.; Litwin-Staszewska, E.; Bockowski, M.; Grzegory, I.; Porowski, S.; Fijalkowski, M.; Rudyk, V.; Tsybulskyi, V.; Panasyuk, M.; Karbovnyk, I.; Kapustianyk, V.

    2016-08-01

    We studied the incorporation of Mg-related impurity centers in GaN crystals depending on the direction of the crystallization front. Two series of GaN crystals - (i) undoped and (ii) Mg-doped - were grown by High Nitrogen Pressure Solution (HNPS) method under otherwise identical conditions. Each series contained four samples with (10 1 bar 0) , (11 2 bar 0) , (20 2 bar 1 bar) and (20 2 bar 1) orientations. The low-temperature photoluminescence (PL) spectroscopy was used for characterization of the obtained crystals. The observed differences in the PL spectra of GaN:Mg crystals suggested that Mg incorporation in GaN grown by HNPS method depends considerably on the orientation of crystallization front. The concentration of Mg impurity incorporated into the GaN crystals subsequently increases for the following sequence of planes: (10 1 bar 0) , (11 2 bar 0) , (20 2 bar 1 bar) and (20 2 bar 1) . For (10 1 bar 0) , (11 2 bar 0) and (20 2 bar 1 bar) planes the blue band is related only to ON - MgGa donor-acceptor pair (DAP) transitions, while for (20 2 bar 1) plane the incorporation of Mg-H complexes occurs additionally to the formation ON - MgGa DAP.

  14. Effect of bulk growth temperature on antiphase domain boundary annihilation rate in MOCVD-grown GaAs on Si(001)

    NASA Astrophysics Data System (ADS)

    Barrett, C. S. C.; Martin, T. P.; Bao, X.-Y.; Kennon, E. L.; Gutierrez, L.; Martin, P.; Sanchez, E.; Jones, K. S.

    2016-09-01

    GaAs is a material of interest as a potential buffer layer in future III-V semiconductor-based transistor technologies integrated on Si wafers. The goal of this study was to investigate the effect of growth temperature on the propagation and annihilation of antiphase domain boundaries (APBs) in GaAs films grown on Si(001) by metal-organic chemical vapor deposition (MOCVD). No intentional wafer off-cuts or high temperature pre-growth anneals (>1000 °C) were employed as both of these practices complicate integration with other devices. To evaluate the role of growth temperature on the APB evolution, a 200 nm thick layer of GaAs was grown on the Si at a fixed temperature of 530 °C so that all samples started with the same approximate APB density. Subsequently, 600 nm of GaAs was grown at temperatures varying between 530 °C and 650 °C. Chemical etching combined with scanning electron microscopy (SEM) was used to profile the density of the APBs in each sample as a function of depth. The APB annihilation rate, i.e. the exponential decay rate of APB density with respect to film thickness, increases from 2.6 μm-1 to 10.7 μm-1 as the growth temperature increases from 530 °C to 610 °C and then saturates. The increase in annihilation rate with increasing temperatures suggests that the higher temperatures remove kinetic barriers to the reduction of the overall APB interfacial area. An activation energy of 1.1 eV was extracted using an Arrhenius relationship and likely corresponds to the energy needed for APBs to kink from {110} to higher-index planes, e.g. {112}. Dark field transmission electron microscopy showed that at higher growth temperatures the APBs can shift from vertical {110} habit planes to {112} planes leading to self-annihilation with sufficient thickness.

  15. Monolithically Integrated InGaAs Nanowires on 3D Structured Silicon-on-Insulator as a New Platform for Full Optical Links.

    PubMed

    Kim, Hyunseok; Farrell, Alan C; Senanayake, Pradeep; Lee, Wook-Jae; Huffaker, Diana L

    2016-03-01

    Monolithically integrated III-V semiconductors on a silicon-on-insulator (SOI) platform can be used as a building block for energy-efficient on-chip optical links. Epitaxial growth of III-V semiconductors on silicon, however, has been challenged by the large mismatches in lattice constants and thermal expansion coefficients between epitaxial layers and silicon substrates. Here, we demonstrate for the first time the monolithic integration of InGaAs nanowires on the SOI platform and its feasibility for photonics and optoelectronic applications. InGaAs nanowires are grown not only on a planar SOI layer but also on a 3D structured SOI layer by catalyst-free metal-organic chemical vapor deposition. The precise positioning of nanowires on 3D structures, including waveguides and gratings, reveals the versatility and practicality of the proposed platform. Photoluminescence measurements exhibit that the composition of ternary InGaAs nanowires grown on the SOI layer has wide tunability covering all telecommunication wavelengths from 1.2 to 1.8 μm. We also show that the emission from an optically pumped single nanowire is effectively coupled and transmitted through an SOI waveguide, explicitly showing that this work lays the foundation for a new platform toward energy-efficient optical links. PMID:26901448

  16. InGaAs focal plane array developments and perspectives

    NASA Astrophysics Data System (ADS)

    Rouvié, A.; Coussement, J.; Huet, O.; Truffer, J. P.; Pozzi, M.; Oubensaid, E. H.; Hamard, S.; Chaffraix, V.; Costard, E.

    2015-05-01

    SWIR spectral band is an attractive domain thanks to its intrinsic properties. Close to visible wavelengths, SWIR images interpretation is made easier for field actors. Besides complementary information can be extracted from SWIR band and bring significant added value in several fields of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control). Among the various new technologies able to detect SWIR wavelengths, InGaAs appears as a key technology. Initially developed for optical telecommunications, this material guaranties performances, stability and reliability and is compatible with attractive production capacity. Thanks to high quality material, very low dark current levels can be achieved at ambient temperature. Then uncooled operation can be set up, allowing compact and low power systems. Since the recent transfer of InGaAs imaging activities from III-Vlab, Sofradir provides a framework for the production activity with the manufacturing of high performances products: CACTUS320 SW. The developments towards VGA format with 15μm pixel pitch, lead today to the industrialization of a new product: SNAKE. On one side, the InGaAs detection array presents high performances in terms of dark current and quantum efficiency. On the other side, the low noise ROIC has different additional functionalities. Then this 640x512 @ 15μm sensor appears as well suited to answer the needs of a wide range of applications. In this paper, we will present the Sofradir InGaAs technology, the performances of our last product SNAKE and the perspectives of InGaAs new developments.

  17. Study on 512×128 pixels InGaAs near infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

    Li, Xue; Tang, Hengjing; Huang, Songlei; Shao, Xiumei; Li, Tao; Huang, Zhangcheng; Gong, Haimei

    2014-10-01

    It is well known that In0.53Ga0.47As epitaxial material is lattice-matched to InP substrate corresponding to the wavelength from 0.9μm to 1.7μm, which results to high quality material and good device characteristics at room temperature. In order to develop the near infrared multi-spectral imaging, 512×128 pixels InGaAs Near Infrared Focal Plane Arrays (FPAs) were studied. The n-InP/i-InGaAs/n-InP double hereto-structure epitaxial material was grown by MBE. The 512×128 back-illuminated planar InGaAs detector arrays were fabricated, including the improvement of passivation film, by grooving the diffusion masking layer, the P type electrode layer, In bump condition and so on. The photo-sensitive region has the diffusion area of 23×23μm2 and pixel pitch of 30×30μm2 . The 512×128 detector arrays were individually hybridized on readout integrated circuit(ROIC) by Indium bump based on flip-chip process to make focal plane arrays (FPAs). The ROIC is based on a capacitive trans-impedance amplifier with correlated double sampling and integrated while readout (IWR) mode with high readout velocity of every pixel resulting in low readout noise and high frame frequency. The average peak detectivity and the response non-uniformity of the FPAs are 1.63×1012 cmHz1/2/W and 5.9%, respectively. The power dissipation and frame frequency of the FPAs are about 180mW and 400Hz, respectively.

  18. Research and experiment of InGaAs shortwave infrared imaging system based on FPGA

    NASA Astrophysics Data System (ADS)

    Ren, Ling; Min, Chaobo; Sun, Jianning; Gu, Yan; Yang, Feng; Zhu, Bo; Pan, Jingsheng; Guo, Yiliang

    2015-04-01

    The design and imaging characteristic experiment of InGaAs shortwave infrared imaging system are introduced. Through the adoption of InGaAs focal plane array, the real time image process structure of InGaAs shortwave infrared imaging system is researched. The hardware circuit and image process software of the imaging system based on FPGA are researched. The InGaAs shortwave infrared imaging system is composed of shortwave infrared lens, InGaAs focal plane array, temperature controller module, power supply module, analog-to-digital converter module, digital-to-analog converter module, FPGA image processing module and optical-mechanical structure. The main lock frequency of InGaAs shortwave infrared imaging system is 30MHz. The output mode of the InGaAs shortwave infrared imaging system is PAL analog signal. The power dissipation of the imaging system is 2.6W. The real time signal process in InGaAs shortwave infrared imaging system includes non-uniformly correction algorithm, bad pixel replacement algorithm, and histogram equalization algorithm. Based on the InGaAs shortwave infrared imaging system, the imaging characteristic test of shortwave infrared is carried out for different targets in different conditions. In the foggy weather, the haze and fog penetration are tested. The InGaAs shortwave infrared imaging system could be used for observing humans, boats, architecture, and mountains in the haze and foggy weather. The configuration and performance of InGaAs shortwave infrared imaging system are respectively logical and steady. The research on the InGaAs shortwave infrared imaging system is worthwhile for improving the development of night vision technology.

  19. Crosstalk study of near infrared InGaAs detectors

    NASA Astrophysics Data System (ADS)

    Li, Xue; Tang, Hengjing; Li, Tao; Fan, Cui; Shao, Xiumei; Li, Jianwei; Wei, Jun; Gong, Haimei

    2016-05-01

    Crosstalk characteristics of high density FPA detectors attract widespread attention in the application of electro-optical systems. Crosstalk characteristics of near-infrared (NIR) InGaAs photodiodes and focal plane arrays (FPAs) were studied in this paper. The mesa type detector was investigated by using laser beam induced current technique (LBIC) to measure the absorption outside the designed photosensitive area, and the results show that the excess absorption enlarges the crosstalk of the adjacent pixels. The structure optimization using the effective absorption layer between the pixels can effectively reduce the crosstalk to 2.5%. The major crosstalk components of the optimization photodiode come from the electronic signal caused by carrier lateral diffusion. For the planar type detectors, test structures were used to compare the crosstalk of different structures, and the guard ring structure shows good suppression of the crosstalk. Then the back-illuminated 32x32 InGaAs photodiodes with 30μm pitch were designed, and LBIC was used to measure its lateral diffusion of the effective carriers and fill factor of photosensitive area. The results indicate that the fill factor of detectors can reach up to 98% when the diffusion region is optimized, and the minimum response exists between two neighborhood pixels. Based on these crosstalk measurement results and optimizing structure designs, the linear InGaAs photodiodes were designed and thus the InGaAs FPA assembly was fabricated. The assembly shows higher electro-optical performance and good improvement on crosstalk. The assembly was applied in infrared imaging system and modulation transfer function (MTF) of FPA assembly was calculated to be above 0.50. The clear image based on FPA assembly was obtained.

  20. Metastable growth of pure wurtzite InGaAs microstructures.

    PubMed

    Ng, Kar Wei; Ko, Wai Son; Lu, Fanglu; Chang-Hasnain, Connie J

    2014-08-13

    III-V compound semiconductors can exist in two major crystal phases, namely, zincblende (ZB) and wurtzite (WZ). While ZB is thermodynamically favorable in conventional III-V epitaxy, the pure WZ phase can be stable in nanowires with diameters smaller than certain critical values. However, thin nanowires are more vulnerable to surface recombination, and this can ultimately limit their performances as practical devices. In this work, we study a metastable growth mechanism that can yield purely WZ-phased InGaAs microstructures on silicon. InGaAs nucleates as sharp nanoneedles and expand along both axial and radial directions simultaneously in a core-shell fashion. While the base can scale from tens of nanometers to over a micron, the tip can remain sharp over the entire growth. The sharpness maintains a high local surface-to-volume ratio, favoring hexagonal lattice to grow axially. These unique features lead to the formation of microsized pure WZ InGaAs structures on silicon. To verify that the WZ microstructures are truly metastable, we demonstrate, for the first time, the in situ transformation from WZ to the energy-favorable ZB phase inside a transmission electron microscope. This unconventional core-shell growth mechanism can potentially be applied to other III-V materials systems, enabling the effective utilization of the extraordinary properties of the metastable wurtzite crystals. PMID:24988280

  1. New developments on InGaAs focal plane array

    NASA Astrophysics Data System (ADS)

    Coussement, J.; Rouvié, A.; Oubensaid, E. H.; Huet, O.; Hamard, S.; Truffer, J.-P.; Pozzi, M.; Maillart, P.; Reibel, Y.; Costard, E.; Billon-Lanfrey, D.

    2014-06-01

    SWIR detection band benefits from natural (sun, night glow, thermal radiation) or artificial (eye safe lasers) photons sources combined to low atmospheric absorption and specific contrast compared to visible wavelengths. It gives the opportunity to address a large spectrum of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control). InGaAs material appears as a good candidate to satisfy SWIR detection needs. The lattice matching with InP constitutes a double advantage to this material: attractive production capacity and uncooled operation thanks to low dark current level induced by high quality material. The recent transfer of imagery activities from III-VLab to Sofradir provides a framework for the production activity with the manufacturing of high performances products: CACTUS320 SW and CACTUS640 SW. The developments, begun at III-Vlab towards VGA format with 15μm pixel pitch, lead today to the industrialization of a new product: SNAKE SW. On one side, the InGaAs detection array presents high performances in terms of dark current and quantum efficiency. On the other side, the low noise ROIC has different additional functionalities. Then this 640×512 @ 15μm module appears as well suited to answer the needs of a wide range of applications. In this paper, we will present the Sofradir InGaAs technology, some performances optimization and the last developments leading to SNAKE SW.

  2. Border trap reduction in Al{sub 2}O{sub 3}/InGaAs gate stacks

    SciTech Connect

    Tang, Kechao; McIntyre, Paul C.; Winter, Roy; Eizenberg, Moshe; Zhang, Liangliang; Droopad, Ravi

    2015-11-16

    The effect of Al{sub 2}O{sub 3} atomic layer deposition (ALD) temperature on the border trap density (N{sub bt}) of Al{sub 2}O{sub 3}/InGaAs gate stacks is investigated quantitatively, and we demonstrate that lowering the trimethylaluminum (TMA)/water vapor ALD temperature from 270 °C to 120 °C significantly reduces N{sub bt}. The reduction of N{sub bt} coincides with increased hydrogen incorporation in low temperature ALD-grown Al{sub 2}O{sub 3} films during post-gate metal forming gas annealing. It is also found that large-dose (∼6000 L) exposure of the In{sub 0.53}Ga{sub 0.47}As (100) surface to TMA immediately after thermal desorption of a protective As{sub 2} capping layer is an important step to guarantee the uniformity and reproducibility of high quality Al{sub 2}O{sub 3}/InGaAs samples made at low ALD temperatures.

  3. Electron and proton damage on InGaAs solar cells having an InP window layer

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Cotal, Hector L.; Walters, Robert J.; Summers, Geoffrey P.

    1995-01-01

    As part of a continuing program to determine the space radiation resistance of InP/ln(0.53)Ga(0.47)As tandem solar cells, n/p In(0.53)Ga(0. 47)As solar cells fabricated by RTI were irradiated with 1 MeV electrons and with 3 MeV protons. The cells were grown with a 3 micron n-lnP window layer to mimic the top cell in the tandem cell configuration for both AMO solar absorption and radiation effects. The results have been plotted against 'displacement damage dose' which is the product of the nonionizing energy loss (NIEL) and the particle fluence. A characteristic radiation damage curve can then be obtained for predicting the effect of all particles and energies. AMO, 1 sun solar illumination IV measurements were performed on the irradiated InGaAs solar cells and a characteristic radiation degradation curve was obtained using the solar cell conversion efficiency as the model parameter. Also presented are data comparing the radiation response of both n/p and p/n (fabricated by NREL) InGaAs solar cells as a function of base doping concentration. For the solar cell efficiency, the radiation degradation was found to be independent of the sample polarity for the same base doping concentration.

  4. Numerical study of the intrinsic recombination carriers lifetime in extended short-wavelength infrared detector materials: A comparison between InGaAs and HgCdTe

    NASA Astrophysics Data System (ADS)

    Wen, Hanqing; Bellotti, Enrico

    2016-05-01

    Intrinsic carrier lifetime due to radiative and Auger recombination in HgCdTe and strained InGaAs has been computed in the extended short-wavelength infrared (ESWIR) spectrum from 1.7 μm to 2.7 μm. Using the Green's function theory, both direct and phonon-assisted indirect Auger recombination rates as well as the radiative recombination rates are calculated for different cutoff wavelengths at 300 K with full band structures of the materials. In order to properly model the full band structures of strained InGaAs, an empirical pseudo-potential model for the alloy is fitted using the virtual crystal approximation with spin-orbit coupling included. The results showed that for InxGa1-xAs grown on InP substrate, the compressive strain, which presents in the film when the cutoff wavelength is longer than 1.7 μm, leads to decrease of Auger recombination rate and increase of radiative recombination rate. Since the dominant intrinsic recombination mechanism in this spectral range is radiative recombination, the overall intrinsic carrier lifetime in the strained InGaAs alloys is shorter than that in the relaxed material. When compared to the relaxed HgCdTe, both relaxed and compressively strained InGaAs alloys show shorter intrinsic carrier lifetime at the same cutoff wavelength in room temperature which confirms the potential advantage of HgCdTe as wide-band infrared detector material. While HgCdTe offers superior performance, ultimately the material of choice for ESWIR application will also depend on material quality and cost.

  5. Lattice-engineered MBE growth of high-indium mole fraction InGaAs for low cost MMICs and (1.3--1.55 {micro}m) OEICs

    SciTech Connect

    Childs, T.T.; Sokolov, V.; Sullivan, C.T.

    1997-11-01

    Using molecular beam epitaxy (MBE) and lattice engineering techniques, the feasibility of combining photonic devices applicable to the 1.3 to 1.55 {micro}m wavelength range and monolithic microwave (or mm-wave) integrated circuits (MMICs) on GaAs is demonstrated. A key factor in the MBE growth is incorporation of an InGaAs active layer having an indium arsenide mole fraction of 0.35 or greater and its lattice compatibility with the underlying semi-insulating GaAs substrate. The InGaAs layer used for the photonic devices, can also serve as the active channel for the high electron mobility transistors (HEMTs) for application in MMICs. Several examples of active and passive photonic devices grown by MBE are presented including an optical ridge waveguide, and a photodetector for detection of light in the 1.3 {micro}m range. The material structure includes a 3-layer AlGaAs/GaAs/AlGaAs optical waveguide and a thin InGaAs absorbing layer situated directly above the optical waveguide. Metal-semiconductor-metal (MSM) photodetectors are formed on the top surface of the InGaAs layer for collection of the photo-induced carriers. The optical ridge waveguide is designed for lateral incidence of the light to enhance the MSM photodetector responsivity. Initial measurements on the optical waveguide and photodetector are presented.

  6. Study of the formation mechanism of InGaAs pyramidal layers on GaAs(100) patterned substrates by LPE

    NASA Astrophysics Data System (ADS)

    Balakrishnan, K.; Iida, S.; Kumagawa, M.; Hayakawa, Y.

    2002-07-01

    A study of the liquid phase epitaxial growth of InxGa1-xAs (x = 0.06) layers on different types of patterned GaAs(100) substrates has been carried out. The dependence of growth morphology on the stripe orientation of the star patterned trench substrate has been observed. Pyramid layers were grown in the stripes oriented along the <001> direction. Broken tent structures formed along the <012> direction. Pyramidal structured layers looked to grow faster than the tent-like and broken tent-like structures. In order to analyse the hollow pyramid structure growth in detail, they were grown on circular trench substrates for different periods of time. Hollow pyramidal structures of InGaAs have been grown on circular patterned trench substrates. Effective defect filtration can be realized in this kind of growth of hollow pyramidal structures. The formation mechanism of the hollow pyramid structured layers has been studied in detail.

  7. Performance limitations of InGaAs photodiodes

    NASA Astrophysics Data System (ADS)

    Rogalski, Antoni

    1999-04-01

    The carrier lifetimes in InxGa1-xAs (InGaAs) ternary alloys for radiative and Auger recombination are calculated for temperature 300 K in the short wavelength range 1.5 < (lambda) < 3.7 micrometers . Due to photon recycling, an order of magnitude enhancements in the radiative lifetimes over those obtained from the standard van Roosbroeck and Shockley expression, has been assumed. The possible Auger recombination mechanisms (CHCC, CHLH and CHSH processes) in direct-gap semiconductors are investigated. In n-type and p-type materials the carrier lifetimes are similar. It is clearly shown that in the range of low doping concentration, the carrier lifetime is determined by radiative recombination. For n-type material in the range of higher doping level, a competition between radiative and CHCC processes take place; instead for p-type materials the most effective channel of Auger mechanisms is the CHSH process. A special attention has been put on discussion of the carrier lifetimes in both types of In0.53Ga0.47As materials. Consequence of enhancement in the radiative lifetime leads to higher ultimate performance of photodiodes. The performance (RoA product) of heterostructure InGaAs photovoltaic devices are analyzed. Both the n-on-p (with p-type active region) as well as p-on- n (with n-type active region) are considered. Finally, theoretically predicted performance of InGaAs photodiodes are compared with experimental data reported by other authors.

  8. Optical properties of stacked InGaAs sidewall quantum wires in InGaAsP/InP

    SciTech Connect

    Zhou, D.; Noetzel, R.; Otten, F.W.M. van; Eijkemans, T.J.; Wolter, J.H.

    2006-05-15

    We report on the optical properties of threefold stacked InGaAs sidewall quantum wires (QWires) with quaternary InGaAsP barriers grown on shallow-patterned InP (311)A substrates by chemical beam epitaxy. Temperature dependent photoluminescence (PL) reveals efficient carrier transfer from the adjacent quantum wells (QWells) into the QWires at low temperature, thermally activated repopulation of the QWells at higher temperature, and negligible localization of carriers along the QWires. Strong broadening of power dependent PL indicates enhanced state filling in the QWires compared to that in the QWells. Clear linear polarization of the PL from the QWires confirms the lateral quantum confinement of carriers. These results demonstrate excellent optical quality of the sidewall QWire structures with room temperature PL peak wavelength at 1.55 {mu}m for applications in fiber-based optical telecommunication systems.

  9. Narrow optical line width from site-controlled InGaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Yang, Lily; Yakes, Michael; Sweeney, Timothy; Carter, Samuel; Kim, Chulsoo; Kim, Mijin; Bracker, Allan; Gammon, Daniel

    2013-03-01

    The incorporation of self-assembled quantum dots (QDs) in systematically scalable quantum devices requires a method of nucleating dots with nanometer-scale spatial accuracy while preserving their narrow optical line width. We have developed a technique combining e-beam lithography, wet etching, and molecular beam epitaxial (MBE) growth to deterministically position InGaAs QDs with spectrometer limited photoluminescence line widths. Our technique takes advantage of the anisotropy in GaAs growth to evolve an etched pattern of holes and lines into faceted structures in which dots nucleate. Using this technique, we were able to grow a buffer layer of pure GaAs up to 90 nm in thickness between the processed surface and the dot nucleation surface, effectively separating the QDs from unavoidable residual defects and impurities on the patterned surface that broaden their optical line widths. Additionally, we demonstrate control over the number of dots nucleating per site, from single to a chain of several, by varying the dimensions of the original pattern. Our dots are grown in a Schottky diode structure. Their PL spectrum shows discrete charging transitions, with narrow linewidths near the spectrometer's resolution limit of 20 micro eV.

  10. Low-dark current 1024×1280 InGaAs PIN arrays

    NASA Astrophysics Data System (ADS)

    Yuan, Ping; Chang, James; Boisvert, Joseph C.; Karam, Nasser

    2014-06-01

    Photon counting imaging applications requires low noise from both detector and readout integrated circuit (ROIC) arrays. In order to retain the photon-counting-level sensitivity, a long integration time has to be employed and the dark current has to be minimized. It is well known that the PIN dark current is sensitive to temperature and a dark current density of 0.5 nA/cm2 was demonstrated at 7 °C previously. In order to restrain the size, weight, and power consumption (SWaP) of cameras for persistent large-area surveillance on small platforms, it is critical to develop large format PIN arrays with small pitch and low dark current density at higher operation temperatures. Recently Spectrolab has grown, fabricated and tested 1024x1280 InGaAs PIN arrays with 12.5 μm pitch and achieved 0.7 nA/cm2 dark current density at 15 °C. Based on our previous low-dark-current PIN designs, the improvements were focused on 1) the epitaxial material design and growth control; and 2) PIN device structure to minimize the perimeter leakage current and junction diffusion current. We will present characterization data and analyses that illustrate the contribution of various dark current mechanisms.

  11. Deep levels in virtually unstrained InGaAs layers deposited on GaAs

    NASA Astrophysics Data System (ADS)

    Pal, D.; Gombia, E.; Mosca, R.; Bosacchi, A.; Franchi, S.

    1998-09-01

    The dislocation-related deep levels in InxGa1-xAs layers grown by molecular beam epitaxy on GaAs substrates have been investigated. Virtually unstrained InGaAs layers with mole fraction x of 0.10, 0.20, and 0.30 have been obtained by properly designing the In composition of linearly graded InxGa1-xAs buffers. Two electron traps, labeled as E2 and E3, whose activation energy scales well with the energy gap, have been found. Unlike E2, E3 shows: (i) a logarithmic dependence of the deep level transient spectroscopy amplitude on the filling pulse width and (ii) an increase of concentration as the buffer/InGaAs interface is approached. These findings, together with the observation that, in compressively strained In0.2Ga0.8As, the E3-related concentration is definitely higher than that of virtually unstrained In0.2Ga0.8As, indicate that this trap is likely originated by extended defects like threading dislocations.

  12. Modeling direct interband tunneling. I. Bulk semiconductors

    SciTech Connect

    Pan, Andrew; Chui, Chi On

    2014-08-07

    Interband tunneling is frequently studied using the semiclassical Kane model, despite uncertainty about its validity. Revisiting the physical basis of this formula, we find that it neglects coupling to other bands and underestimates transverse tunneling. As a result, significant errors can arise at low and high fields for small and large gap materials, respectively. We derive a simple multiband tunneling model to correct these defects analytically without arbitrary parameters. Through extensive comparison with band structure and quantum transport calculations for bulk InGaAs, InAs, and InSb, we probe the accuracy of the Kane and multiband formulas and establish the superiority of the latter. We also show that the nonlocal average electric field should be used when applying either of these models to nonuniform potentials. Our findings are important for efficient analysis and simulation of bulk semiconductor devices involving tunneling.

  13. Low dark current InGaAs detector arrays for night vision and astronomy

    NASA Astrophysics Data System (ADS)

    MacDougal, Michael; Geske, Jon; Wang, Chad; Liao, Shirong; Getty, Jonathan; Holmes, Alan

    2009-05-01

    Aerius Photonics has developed large InGaAs arrays (1K x 1K and greater) with low dark currents for use in night vision applications in the SWIR regime. Aerius will present results of experiments to reduce the dark current density of their InGaAs detector arrays. By varying device designs and passivations, Aerius has achieved a dark current density below 1.0 nA/cm2 at 280K on small-pixel, detector arrays. Data is shown for both test structures and focal plane arrays. In addition, data from cryogenically cooled InGaAs arrays will be shown for astronomy applications.

  14. Study of InGaAs based MODFET structures using variable angle spectroscopic ellipsometry

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Sieg, R. M.; Yao, H. D.; Snyder, P. G.; Woollam, J. A.; Pamulapati, J.; Bhattacharya, P. K.; Sekula-Moise, P. A.

    1991-01-01

    Variable angle spectroscopic ellipsometry was used to estimate the thicknesses of all layers within the optical penetration depth of InGaAs based MODFET structures. Strained and unstrained InGaAs channels were made by MBE on InP substrates and by MOCVD on GaAs substrates. In most cases, ellipsometrically determined thicknesses were within 10 percent of the growth calibration results. The MBE made InGaAs strained layers showed large strain effects, indicating a probable shift in the critical points of their dielectric function toward the InP lattice matched concentration.

  15. Lattice-matched and strained InGaAs solar cells for thermophotovoltaic use

    SciTech Connect

    Jain, R.K.; Wilt, D.M.; Jain, R.; Landis, G.A.; Flood, D.J.

    1996-02-01

    Lattice-matched and strained indium gallium arsenide solar cells can be used effectively and efficiently for thermophotovoltaic applications. A 0.75 eV bandgap InGaAs solar cell is well matched to a 2000 K blackbody source with a emission peak around 1.5 {mu}m. A 0.60 eV bandgap InGaAs cell is well suited to a Ho-YAG selective emitter and a blackbody at 1500 K which have emission peak around 2.0 {mu}m. Modeling results predict that the cell efficiencies in excess of 30{percent} are possible for the 1500 K Ho-YAG selective emitter (with strained InGaAs) and for the 2000 K blackbody (with lattice-matched InGaAs) sources. {copyright} {ital 1996 American Institute of Physics.}

  16. 4x4 Individually Addressable InGaAs APD Arrays Optimized for Photon Counting Applications

    NASA Technical Reports Server (NTRS)

    Gu, Y.; Wu, X.; Wu, S.; Choa, F. S.; Yan, F.; Shu, P.; Krainak, M.

    2007-01-01

    InGaAs APDs with improved photon counting characteristics were designed and fabricated and their performance improvements were observed. Following the results, a 4x4 individually addressable APD array was designed, fabricated, and results are reported.

  17. Characterization of NIR InGaAs imager arrays for the JDEM SNAPmission concept

    SciTech Connect

    Seshadri, S.; Cole, M.D.; Hancock, B.; Ringold, P.; Wrigley, C.; Bonati, M.; Brown, M.G.; Schubnell, M.; Rahmer, G.; Guzman, D.; Figer,D.; Tarle, G.; Smith, R.M.; Bebek, C.

    2006-05-23

    We present the results of a study of the performance of InGaAs detectors conducted for the SuperNova Acceleration Probe (SNAP) dark energy mission concept. Low temperature data from a nominal 1.7um cut-off wavelength 1kx1k InGaAs photodiode array, hybridized to a Rockwell H1RG multiplexer suggest that InGaAs detector performance is comparable to those of existing 1.7um cut-off HgCdTe arrays. Advances in 1.7um HgCdTe dark current and noise initiated by the SNAP detector research and development program makes it the baseline detector technology for SNAP. However, the results presented herein suggest that existing InGaAs technology is a suitable alternative for other future astronomy applications.

  18. InGaAs Detectors for Miniature Infrared Instruments

    NASA Technical Reports Server (NTRS)

    Krabach, T. N.; Staller, C.; Dejewski, S.; Cunningham, T.; Herring, M.; Fossum, E. R.

    1993-01-01

    In the past year, there has been substantial impetus for NASA to consider missions that are of relatively low cost as a trade off for a higher new mission launch rate. To maintain low mission cost, these missions will be of short duration and will use smaller launch vehicles (e.g. Pegasus). Consequently, very low volume, very low mass instrument (a.k.a. miniature instrument) payloads will be required. Furthermore, it is anticipated that the number of instruments flown on a particular mission will also be highly constrained; consequently increased instrument capability will also be desired. In the case of infrared instruments, focal planes typically require cooling to ensure high performance of the detectors, especially in the case of spectrometers where high D* is necessary. In this paper, we discuss the InGaAs detector technology and its potential.

  19. Dimensionality of InGaAs nonlinear optical response

    SciTech Connect

    Bolton, S.R. |

    1995-07-01

    In this thesis the ultrafast optical properties of a series of InGaAs samples ranging from the two to the three dimensional limit are discussed. An optical system producing 150 fs continuum centered at 1.5 microns was built. Using this system, ultrafast pump-probe and four wave mixing experiments were performed. Carrier thermalization measurements reveal that screening of the Coulomb interaction is relatively unaffected by confinement, while Pauli blocking nonlinearities at the band edge are approximately twice as strong in two dimensions as in three. Carrier cooling via phonon emission is influenced by confinement due both to the change in electron distribution function and the reduction in electron phonon coupling. Purely coherent band edge effects, as measured by the AC Stark effect and four wave mixing, are found to be dominated by the changes in excitonic structure which take place with confinement.

  20. Compound semiconductors grown on porous alumina substrate as a novel hydrogen permeation membrane

    NASA Astrophysics Data System (ADS)

    Sato, Michio

    2007-01-01

    A highly p-type-doped InGaAs film was grown on a porous alumina substrate by metalorganic chemical vapor deposition (MOCVD). This structure was proposed as a novel hydrogen selective permeation membrane. In the p-type film, hydrogen atoms are converted to protons by giving their electrons to the dopant atoms. The protons easily diffuse in the film at elevated temperatures and are desorbed as hydrogen molecules from the surface of the film. When the hydrogen gas is supplied to both side of the film and there is difference in pressure, only hydrogen can penetrate into the film and move to the lower-pressure side. Preliminary experimental results are shown in this paper. Large amount of hydrogen was found in both the epitaxial InGaAs film (grown on InP) and the poly-crystal InGaAs films (grown on sapphire and porous alumina). Hydrogen was desorbed when the film was annealed in nitrogen gas. Hydrogen was absorbed into the film again by annealing in hydrogen gas. Scanning electron microscope (SEM) pictures suggest that a dense poly-crystal film without pin-holes was grown on the porous alumina substrate.

  1. Radiative efficiency of MOCVD grown QD lasers

    NASA Astrophysics Data System (ADS)

    Mawst, Luke; Tsvid, Gene; Dudley, Peter; Kirch, Jeremy; Park, J. H.; Kim, N.

    2010-02-01

    The optical spectral gain characteristics and overall radiative efficiency of MOCVD grown InGaAs quantum dot lasers have been evaluated. Single-pass, multi-segmented amplified spontaneous emission measurements are used to obtain the gain, absorption, and spontaneous emission spectra in real units. Integration of the calibrated spontaneous emission spectra then allows for determining the overall radiative efficiency, which gives important insights into the role which nonradiative recombination plays in the active region under study. We use single pass, multi-segmented edge-emitting in which electrically isolated segments allow to vary the length of a pumped region. In this study we used 8 section devices (the size of a segment is 50x300 μm) with only the first 5 segments used for varying the pump length. The remaining unpumped segments and scribed back facet minimize round trip feedback. Measured gain spectra for different pump currents allow for extraction of the peak gain vs. current density, which is fitted to a logarithmic dependence and directly compared to conventional cavity length analysis, (CLA). The extracted spontaneous emission spectrum is calibrated and integrated over all frequencies and modes to obtain total spontaneous radiation current density and radiative efficiency, ηr. We find ηr values of approximately 17% at RT for 5 stack QD active regions. By contrast, high performance InGaAs QW lasers exhibit ηr ~50% at RT.

  2. Growing InGaAs quasi-quantum wires inside semi-rhombic shaped planar InP nanowires on exact (001) silicon

    NASA Astrophysics Data System (ADS)

    Han, Yu; Li, Qiang; Chang, Shih-Pang; Hsu, Wen-Da; Lau, Kei May

    2016-06-01

    We report InGaAs quasi-quantum wires embedded in planar InP nanowires grown on (001) silicon emitting in the 1550 nm communication band. An array of highly ordered InP nanowire with semi-rhombic cross-section was obtained in pre-defined silicon V-grooves through selective-area hetero-epitaxy. The 8% lattice mismatch between InP and Si was accommodated by an ultra-thin stacking disordered InP/GaAs nucleation layer. X-ray diffraction and transmission electron microscope characterizations suggest excellent crystalline quality of the nanowires. By exploiting the morphological evolution of the InP and a self-limiting growth process in the V-grooves, we grew embedded InGaAs quantum-wells and quasi-quantum-wires with tunable shape and position. Room temperature analysis reveals substantially improved photoluminescence in the quasi-quantum wires as compared to the quantum-well reference, due to the reduced intrusion defects and enhanced quantum confinement. These results show great promise for integration of III-V based long wavelength nanowire lasers on the well-established (001) Si platform.

  3. Comparison of Ge, InGaAs p-n junction solar cell

    NASA Astrophysics Data System (ADS)

    Korun, M.; Navruz, T. S.

    2016-04-01

    In this paper, the effect of material parameters on the efficiency of Ge and InGaAs p-n junction solar cells which are most commonly used as the sub-cell of multi-junction solar cells are investigated and the results due to these two cells are compared. The efficiency of Ge (EG =0.67 eV) solar cell which is easy to manufacture and inexpensive in cost, is compared with the efficiency of InGaAs (EG =0.74 eV) solar cell which is coming with drawback of high production difficulties and cost. The theoretical efficiency limit of Ge and InGaAs solar cells with optimum thickness were determined by using detailed balance model under one sun AM1.5 illumination. Since the band gap values of two cells are close to each other, approximate detailed balance efficiency limits of 16% for InGaAs and 14% for Ge are obtained. When drift-diffusion model is used and the thicknesses and doping concentrations are optimized, the maximum efficiency values are calculated as 13% for InGaAs and 9% for Ge solar cell. For each solar cell external quantum efficiency curves due to wavelength are also sketched and compared.

  4. Bulk undercooling

    NASA Technical Reports Server (NTRS)

    Kattamis, T. Z.

    1984-01-01

    Bulk undercooling methods and procedures will first be reviewed. Measurement of various parameters which are necessary to understand the solidification mechanism during and after recalescence will be discussed. During recalescence of levitated, glass-encased large droplets (5 to 8 mm diam) high speed temperature sensing devices coupled with a rapid response oscilloscope are now being used at MIT to measure local thermal behavior in hypoeutectic and eutectic binary Ni-Sn alloys. Dendrite tip velocities were measured by various investigators using thermal sensors or high speed cinematography. The confirmation of the validity of solidification models of bulk-undercooled melts is made difficult by the fineness of the final microstructure, the ultra-rapid evolution of the solidifying system which makes measurements very awkward, and the continuous modification of the microstructure which formed during recalescence because of precipitation, remelting and rapid coarsening.

  5. Research in the modulation transfer function (MTF) measurement of InGaAs focal plane arrays

    NASA Astrophysics Data System (ADS)

    Xu, Zhonghua; Fang, Jiaxiong

    2012-10-01

    The Modulation Transfer Function (MTF) of an opto-electrical device is defined as the ratio of the system output modulation to the input modulation, which describes the performance of the imaging system in the Fourier domain. Accurate measurement of the MTF is often obtained by analyzing the high-quality image of a special target reproduced by the optical system with known MTF. To evaluate the MTF of short-wave infrared InGaAs focal plane arrays (FPAs), we develop a laboratory system with high precision and automation based on the slit scan method. An 8*1 linear InGaAs FPAs is then measured by this test set-up for the first time to evaluate the MTF of each pixel at room temperature. The results show a good MTF repeatability and uniformity of the 8*1 InGaAs FPAs. The relationship between the MTF and illumination is also discussed.

  6. Formation of columnar (In,Ga)As quantum dots on GaAs(100)

    SciTech Connect

    He, J.; Noetzel, R.; Offermans, P.; Koenraad, P.M.; Gong, Q.; Hamhuis, G.J.; Eijkemans, T.J.; Wolter, J.H.

    2004-10-04

    Columnar (In,Ga)As quantum dots (QDs) with homogeneous composition and shape in the growth direction are realized by molecular-beam epitaxy on GaAs(100) substrates. The columnar (In,Ga)As QDs are formed on InAs seed QDs by alternating deposition of thin GaAs intermediate layers and monolayers of InAs with extended growth interruptions after each layer. The height of the columnar (In,Ga)As QDs is controlled by varying the number of stacked GaAs/InAs layers. The structural and optical properties are studied by cross-sectional scanning tunneling microscopy, atomic force microscopy, and photoluminescence spectroscopy. With increase of the aspect ratio of the columnar QDs, the emission wavelength is redshifted and the linewidth is reduced.

  7. Liquid phase electroepitaxial bulk growth of binary and ternary alloy semiconductors under external magnetic field

    NASA Astrophysics Data System (ADS)

    Sheibani, Hamdi

    2002-01-01

    Liquid Phase Electroepitaxy (LPEE) and is a relatively new, promising technique for producing high quality, thick compound semiconductors and their alloys. The main objectives are to reduce the adverse effect of natural convection and to determine the optimum growth conditions for reproducible desired crystals for the optoelectronic and electronic device industry. Among the available techniques for suppressing the adverse effect of natural convection, the application of an external magnetic field seems the most feasible one. The research work in this dissertation consists of two parts. The first part is focused on the design and development of a state of the art LPEE facility with a novel crucible design, that can produce bulk crystals of quality higher than those achieved by the existing LPEE system. A growth procedure was developed to take advantage of this novel crucible design. The research of the growth of InGaAs single crystals presented in this thesis will be a basis for the future LPEE growth of other important material and is an ideal vehicle for the development of a ternary crystal growth process. The second part of the research program is the experimental study of the LPEE growth process of high quality bulk single crystals of binary/ternary semiconductors under applied magnetic field. The compositional uniformity of grown crystals was measured by Electron Probe Micro-analysis (EPMA) and X-ray microanalysis. The state-of-the-art LPEE system developed at University of Victoria, because of its novel design features, has achieved a growth rate of about 4.5 mm/day (with the application of an external fixed magnetic field of 4.5 KGauss and 3 A/cm2 electric current density), and a growth rate of about 11 mm/day (with 4.5 KGauss magnetic field and 7 A/cm2 electric current density). This achievement is simply a breakthrough in LPEE, making this growth technique absolutely a bulk growth technique and putting it in competition with other bulk growth techniques

  8. The influence of sunlight irradiation on the characteristics of InGaAs detectors

    NASA Astrophysics Data System (ADS)

    Shao, Xiumei; Zhu, Yaoming; Li, Xue; Tang, Hengjing; Li, Tao; Gong, Haimei

    2014-10-01

    InGaAs ternary compound is suitable for detector applications in the shortwave infrared (SWIR) band. Due to the advantages of good stability, low cooling requirements and high detectivity, InGaAs detectors have been applied widely in the space remote sensing area. However, InGaAs detectors would be affected by strong sunlight direct irradiation in space application. In this paper, a mesa-type InGaAs detector with large sensitive area of diameter 5mm was designed based on InP/In0.53Ga0.47As/InP epitaxial material, which is lattice-matched to InP substrate. The InGaAs detectors were fabricated by ICP etching, and packaged in a Kovar shell. The relative spectral response is in the range of 0.9μm to 1.7μm. The mechanism of the sunlight direct irradiation on InGaAs detector performance was studied. The sunlight were focalized by lens and irradiated directly on the detector. A piece of epitaxial material was investigated at the same time which was cleaved from a 2 inch wafer, same to the detector material. The real time testing was taken out to observe the output signal of the detector. After the irradiation experiment, the I-V curves and the relative response were tested immediately. The dark current of the detector increased temporarily, but come back to the original level after 24 hours. The response spectrum was nearly not affected. The XRD testing of the epitaxial material sample was carried out before and after sunlight direct irradiation. The sunlight irradiation causes thermal stress degradation. The thermal electrons were produced by the absorption of a great deal of visible light, leading to local enhancement of temperature and the lattice degeneration of the material.

  9. Passivation of InGaAs surfaces with an integrated process including an ammonia DECR plasma

    SciTech Connect

    Lescaut, B.; Nissim, Y.I.; Bresse, J.F.

    1996-12-31

    Stable and optimum characteristics of micro-optoelectronic devices and circuits require the passivation of the free surface of the III-V materials. An integrated process using a combination of surface cleaning and photochemical dielectric encapsulation is proposed for passivation. The passivation of InGaAs with a short ammonia plasma cleaning has been obtained. The treated surface has been protected with a photochemical dielectric encapsulation. MIS structures fabricated on treated InGaAs surfaces have shown a low density of interface traps and a small hysteresis. This process is an integration of two cold processes that enable its use at the end of the process fabrication of circuits.

  10. InGaAs monolithic interconnected modules (MIM)

    SciTech Connect

    Fatemi, N.S.; Jenkins, P.P.; Weizer, V.G.; Hoffman, R.W. Jr.; Wilt, D.M.; Scheiman, D.; Brinker, D.; Murray, C.S.; Riley, D.

    1997-12-31

    A monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM device consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Also, the use of a BSR obviates the need to use a separate filtering element. As a result, MIMs are exposed to the entire emitter output, thereby maximizing output power density. MIMs with an active area of 1 x 1-cm were comprised of 15 cells monolithically connected in series. Both lattice-matched and lattice-mismatched InGaAs/InP devices were produced, with bandgaps of 0.74 and 0.55 eV, respectively. The 0.74-eV modules demonstrated an open-circuit voltage (Voc) of 6.158 V and a fill factor of 74.2% at a short-circuit current (Jsc) of 842 mA/cm{sup 2}, under flashlamp testing. The 0.55-eV modules demonstrated a Voc of 4.849 V and a fill factor of 57.8% at a Jsc of 3.87 A/cm{sup 2}. IR reflectance measurements (i.e., {lambda} > 2 {micro}m) of these devices indicated a reflectivity of {ge} 83%. Latest electrical and optical performance results for the MIMs will be presented.

  11. InGaAs monolithic interconnected modules (MIMs)

    SciTech Connect

    Fatemi, N.S.; Jenkins, P.P.; Weizer, V.G.; Hoffman, R.W. Jr.; Wilt, D.M.; Scheiman, D.; Brinker, D.; Murray, C.S.; Riley, D.

    1997-12-31

    A monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM device consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the radiator for recuperation, thereby providing for high system efficiencies. Also, the use of a BSR reduces the requirements imposed on a front surface interference filter and may lead to using only an anti-reflection coating. As a result, MIMs are exposed to the entire radiator output, and with increasing output power density. MIMs were fabricated with an active area of 0.9 x 1 cm, and with 15 cells monolithically connected in series. Both lattice-matched and lattice-mismatched InGaAs/InP devices were fabricated, with bandgaps of 0.74 and 0.55 eV, respectively. The 0.74 eV MIMs demonstrated an open-circuit voltage (Voc) of 6.16 V and a fill factor of 74.2% at a short-circuit current (Jsc) of 0.84 A/cm{sup 2}, under flashlamp testing. The 0.55 eV modules demonstrated a Voc of 4.85 V and a fill factor of 57.8% at a Jsc of 3.87 A/cm{sup 2}. The near IR reflectance (2--4 {micro}m) for both lattice-matched and lattice-mismatched structures was measured to be in the range of 80--85%. Latest electrical and optical performance results for these MIMs is presented.

  12. Monolithic integration of 1.3-μm InGaAs photodetectors and high-electron-mobility transistor (HEMT) electronic circuits on GaAs

    NASA Astrophysics Data System (ADS)

    Fink, Thomas; Hurm, Volker; Raynor, Brian; Koehler, Klaus; Benz, Willy; Ludwig, M.

    1995-04-01

    For the first time, monolithic optoelectronic receivers for a wavelength of 1.3 micrometers have been fabricated successfully on GaAs substrates using InGaAs metal-semiconductor-metal (MSM) photodiodes and AlGaAs/GaAs/AlGaAs high-electron-mobility transistors (HEMTs). Using molecular beam epitaxy (MBE), the photodetector layers were grown on top of a double (delta) -doped AlGaAs/GaAs/AlGaAs HEMT structure which allows the fabrication of enhancement and depletion field effect transistors. The photoabsorbing InGaAs layer was grown at 500 degree(s)C. To fabricate the optoelectronic receivers, first, an etch process using a combination of non-selective wet etching and selective reactive ion etching was applied to produce mesas for the photoconductors and to uncover the HEMT structure in all other areas. For the electronic circuits, our well-established HEMT process for 0.3-micrometers transistor gates was used which includes electron-beam lithography for gate definition and optical lithography for NiCr thin films resistors, capacitors, and inductors. The interdigitated MSM photodiode fingers were also fabricated using electron-beam lithography. For interconnecting the electronic circuits and the photodetectors, air bridges were employed. The entire process was performed on 2-inch wafers with more than 90% yield of functional receivers. The finished receiver--basically an MSM photodetector linked to a transimpedance amplifier--is operational at an incident wavelength of 1.3 micrometers at data rates up to 1.2 Gbit/s. The sensitivity of the detectors is 0.16 A/W at a 10 V bias.

  13. InGaAs PIN photodiodes on semi-insulating InP substrates with bandwidth exceeding 14 GHz

    NASA Astrophysics Data System (ADS)

    Wen-Jeng Ho; Ting-Arn Dai; Zuon-Ming Chuang; Wei Lin; Yuan-Kuang Tu; Meng-Chyi Wu

    1995-07-01

    The top-illuminated InGaAs PIN photodiodes have been fabricated from materials grown by metalorganic vapor phase epitaxy. Using the planar air-bridge approach and the selective etching technique, it can eliminate the significant bondpad capacitance which is present in conventional PIN photodiodes on conducting substrates. Besides, a self-aligned lift-off process is used for the n-contact recess and metallization. The anti-reflection coating devices have responsivity of 0.79 and 0.78 A/W at 1.3 and 1.55 μm, respectively. The fabricated devices with 30 μm photosensitive diameter have a very low dark current below 0.2 nA and low capacitance of 143 fF at -5V bias voltage. The 3-dB bandwidth of these devices is in excess of 14.8 GHz which is in good agreement with the calculated minority-carrier transit time through an absorbing layer thickness of 1.85 μm. The device performance reveals that these devices are potentially suitable for the applications in optoelectronic integrated circuits.

  14. InGaAs self-assembly quantum dot for high-speed 1300 nm electroabsorption modulator

    NASA Astrophysics Data System (ADS)

    Lin, Chuan-Han; Wu, Jui-pin; Kuo, Yu-zheng; Chiu, Yi-jen; Tzeng, T. E.; Lay, T. S.

    2011-05-01

    In this paper, a new type of high-speed electroabsorption modulator (EAM) based on quantum dot (QD) p-i-n heterostructure is demonstrated. The QD layers sandwiched by p-AlGaAs and n-AlGaAs are grown by multilayer InGaAs self-assembled QD with luminance wavelength of 1300 nm, serving as the active region of EAM. The photocurrent spectrum measurement exhibits a red shift of 15 nm in QD transition energy levels on biasing from 0 to 6 V. A quadratic relation of energy shift against the reversed bias is extracted, confirming the quantum-confined Stark effect (QCSE) in QD. On fabricating a 300 μm long EAM, as high as DC 5 dB extinction ratio by 6 V voltage swing at 1310 nm is observed. As compared with well-developed quantum well (QW) EAM (well thickness ∼10 nm) of the same length, the lower density of states still shows the same order of magnitude in extinction ratio, suggesting strong QCSE in such 3-dimensional confined QD. An electrical-to-optical conversion with -3 dB bandwidth of 3.3 GHz is also attained in such QD EAM, where the speed is mainly limited by the parasitic capacitance on substrate. It implies that through optimization of QD and device structures, the advantages of QD properties are quite promising to be used in high-speed optoelectronic fields.

  15. Comparison of low temperature photoluminescence of bulk MBE (Molecular Beam Epitaxy) grown AlGaAs and GaAs using a graphite generated dimer versus a standard tetramer arsenic group-V source

    SciTech Connect

    Brennan, T.M.; Hammons, B.E.; Smith, M.C.; Jones, E.D.

    1987-01-01

    The carbon concentrations in GaAs and AlGaAs grown by Molecular Beam Epitaxy (MBE) have been studied when a graphite generated dimeric arsenic species and a standard tetramer arsenic species are used as the group-V source. Photoluminescence and Van der Pauw-Hall measurements have been made to examine the material quality in reference to which arsenic species is used for film growth. Results indicate that a graphite crucible arrangement for the thermal cracking of As/sub 4/ produces significant carbon contamination and is unacceptable for the MBE growth of GaAs and AlGaAs. 15 refs., 3 figs.

  16. A carrier relaxation bottleneck probed in single InGaAs quantum dots using integrated superconducting single photon detectors

    SciTech Connect

    Reithmaier, G. Flassig, F.; Hasch, P.; Lichtmannecker, S.; Kaniber, M.; Müller, K.; Vučković, J.; Gross, R.; Finley, J. J.

    2014-08-25

    Using integrated superconducting single photon detectors, we probe ultra-slow exciton capture and relaxation dynamics in single self-assembled InGaAs quantum dots embedded in a GaAs ridge waveguide. Time-resolved luminescence measurements performed with on- and off-chip detection reveal a continuous decrease in the carrier relaxation time from 1.22 ± 0.07 ns to 0.10 ± 0.07 ns upon increasing the number of non-resonantly injected carriers. By comparing off-chip time-resolved spectroscopy with spectrally integrated on-chip measurements, we identify the observed dynamics in the rise time (τ{sub r}) as arising from a relaxation bottleneck at low excitation levels. From the comparison with the temporal dynamics of the single exciton transition with the on-chip emission signal, we conclude that the relaxation bottleneck is circumvented by the presence of charge carriers occupying states in the bulk material and the two-dimensional wetting layer continuum. A characteristic τ{sub r} ∝ P{sup −2∕3} power law dependence is observed suggesting Auger-type scattering between carriers trapped in the quantum dot and the two-dimensional wetting layer continuum which circumvents the phonon relaxation bottleneck.

  17. Characteristics of Monolithically Integrated InGaAs Active Pixel Imager Array

    NASA Technical Reports Server (NTRS)

    Kim, Q.; Cunningham, T. J.; Pain, B.; Lange, M. J.; Olsen, G. H.

    2000-01-01

    Switching and amplifying characteristics of a newly developed monolithic InGaAs Active Pixel Imager Array are presented. The sensor array is fabricated from InGaAs material epitaxially deposited on an InP substrate. It consists of an InGaAs photodiode connected to InP depletion-mode junction field effect transistors (JFETs) for low leakage, low power, and fast control of circuit signal amplifying, buffering, selection, and reset. This monolithically integrated active pixel sensor configuration eliminates the need for hybridization with silicon multiplexer. In addition, the configuration allows the sensor to be front illuminated, making it sensitive to visible as well as near infrared signal radiation. Adapting the existing 1.55 micrometer fiber optical communication technology, this integration will be an ideal system of optoelectronic integration for dual band (Visible/IR) applications near room temperature, for use in atmospheric gas sensing in space, and for target identification on earth. In this paper, two different types of small 4 x 1 test arrays will be described. The effectiveness of switching and amplifying circuits will be discussed in terms of circuit effectiveness (leakage, operating frequency, and temperature) in preparation for the second phase demonstration of integrated, two-dimensional monolithic InGaAs active pixel sensor arrays for applications in transportable shipboard surveillance, night vision, and emission spectroscopy.

  18. 256×1 element linear InGaAs short wavelength near-infrared detector arrays

    NASA Astrophysics Data System (ADS)

    Li, Xue; Tang, Hengjing; Fan, Guangyu; Liu, Dafu; Shao, Xiumei; Zhang, Yonggang; Zhang, Haiyan; Chen, Xinyu; Zhu, Sangen; Gong, Haimei; Fang, Jiaxiong

    2008-03-01

    256×1 element linear InGaAs detector arrays assembly have been fabricated for the short wave infrared band(0.9~1.7μm), including the detector, CMOS readout circuits, thermoelectric cooler in a sealed package. The InGaAs detectors were achieved by mesa structure on the p-InP/i-InGaAs/n-InP double hetero-structure epitaxial material. 256×1 element linear InGaAs detectors were wire-bonded to 128×1 element odd and even ROIC, which were packaged in a dual-in-line package by parallel sealing. The characteristics of detectors and detector arrays module were investigated at the room temperature. The detector shows response peak at 1.62μm with 50% cutoff wavelength of 1.73μm and average R0A with 5.02KΩ•cm2. Response non-uniformity and average peak detectivity of 256×1 element linear InGaAs detector arrays are 3.10% and 1.38×10 12cmHz 1/2/W, respectively.

  19. (In,Ga)As sidewall quantum wires on shallow-patterned InP (311)A

    SciTech Connect

    Zhou, D.; Noetzel, R.; Gong, Q.; Offermans, P.; Koenraad, P.M.; Veldhoven, P.J. van; Otten, F.W.M. van; Eijkemans, T.J.; Wolter, J.H.

    2005-03-15

    (In,Ga)As sidewall quantum wires (QWires) are realized by chemical beam epitaxy along [01-1] mesa stripes on shallow-patterned InP (311)A substrates. The QWires exhibit strong lateral carrier confinement due to larger thickness and In composition compared to the adjacent quantum wells, as determined by cross-sectional scanning-tunneling microscopy and microphotoluminescence (micro-PL) spectroscopy. The PL of the (In,Ga)As QWires with InP and quaternary (Ga,In)(As,P) barriers reveals narrow linewidth, high efficiency, and large lateral carrier confinement energies of 60-70 meV. The QWires are stacked in growth direction with identical PL peak emission energy. The PL emission energy is not only controlled by the (In,Ga)As layer thickness but also by the patterned mesa height. Stacked (In,Ga)As QWires with quaternary barriers exhibit room temperature PL emission at 1.55 {mu}m in the technologically important wavelength region for telecommunication applications.

  20. Microsecond-long lasing delays in thin P-clad InGaAs QW lasers

    SciTech Connect

    Wu, C.H.; Miester, C.F; Zory, P.S.; Emanuel, M.A.

    1996-06-01

    Microsecond-long lasing delays have been observed in wide-stripe, thin p-clad, InGaAs single quantum well (QW) lasers with ``thick`` p{sup +} cap layers. Computer modeling indicates that localized refractive index changes in the cap layer due to ohmic heating from the con- tact resistance may be the root cause.

  1. Development of a Quantum Dot, 0.6 eV InGaAs Thermophotovoltaic (TPV) Converter

    NASA Technical Reports Server (NTRS)

    Forbes, David; Sinharoy, Samar; Raffalle, Ryne; Weizer, Victor; Homann, Natalie; Valko, Thomas; Bartos,Nichole; Scheiman, David; Bailey, Sheila

    2007-01-01

    Thermophotovoltaic (TPV) power conversion has to date demonstrated conversion efficiencies exceeding 20% when coupled to a heat source. Current III-V semiconductor TPV technology makes use of planar devices with bandgaps tailored to the heat source. The efficiency can be improved further by increasing the collection efficiency through the incorporation of InAs quantum dots. The use of these dots can provide sub-gap absorption and thus improve the cell short circuit current without the normal increase in dark current associated with lowering the bandgap. We have developed self-assembled InAs quantum dots using the Stranski-Krastanov growth mode on 0.74 eV In0.53GaAs lattice-matched to InP and also on lattice-mismatched 0.6 eV In0.69GaAs grown on InP through the use of a compositionally graded InPAsx buffer structure, by metalorganic vapor phase epitaxy (MOVPE). Atomic force microscopy (AFM) measurements showed that the most reproducible dot pattern was obtained with 5 monolayers of InAs grown at 450 C. The lattice mismatch between InAs and In0.69GaAs is only 2.1%, compared to 3.2% between InAs and In0.53GaAs. The smaller mismatch results in lower strain, making dot formation somewhat more complicated, resulting in quantum dashes, rather than well defined quantum dots in the lattice-mismatched case. We have fabricated 0.6 eV InGaAs planer TPV cells with and without the quantum dashes

  2. Nanophotonic integrated circuits from nanoresonators grown on silicon

    NASA Astrophysics Data System (ADS)

    Chen, Roger; Ng, Kar Wei; Ko, Wai Son; Parekh, Devang; Lu, Fanglu; Tran, Thai-Truong D.; Li, Kun; Chang-Hasnain, Connie

    2014-07-01

    Harnessing light with photonic circuits promises to catalyse powerful new technologies much like electronic circuits have in the past. Analogous to Moore’s law, complexity and functionality of photonic integrated circuits depend on device size and performance scale. Semiconductor nanostructures offer an attractive approach to miniaturize photonics. However, shrinking photonics has come at great cost to performance, and assembling such devices into functional photonic circuits has remained an unfulfilled feat. Here we demonstrate an on-chip optical link constructed from InGaAs nanoresonators grown directly on a silicon substrate. Using nanoresonators, we show a complete toolkit of circuit elements including light emitters, photodetectors and a photovoltaic power supply. Devices operate with gigahertz bandwidths while consuming subpicojoule energy per bit, vastly eclipsing performance of prior nanostructure-based optoelectronics. Additionally, electrically driven stimulated emission from an as-grown nanostructure is presented for the first time. These results reveal a roadmap towards future ultradense nanophotonic integrated circuits.

  3. Comparison and implications of charge collection measurements in silicon and InGaAs irradiated by energetic protons and neutrons

    SciTech Connect

    Normand, E.; Oberg, D.L.; Wert, J.L.

    1995-12-01

    A variety of charge collection measurements by energetic protons and neutrons have been measured and compared. These include deposition in: small silicon junctions, large volume American and russian silicon surface barrier detectors, and InGaAs photodiodes.

  4. Growth and properties of InGaAs/FeAl/InAlAs/InP heterostructures for buried reflector/interconnect applications in InGaAs thermophotovoltaic devices

    SciTech Connect

    Ringel, S.A.; Sacks, R.N.; Qin, L.; Clevenger, M.B.; Murray, C.S.

    1998-11-01

    Thermophotovoltaic cells consisting of InGaAs active layers are of extreme promise for high efficiency, low bandgap TPV conversion. In the monolithic interconnected module configuration, the presence of the InGaAs lateral conduction layer (LCL) necessary for the series connection between TPV cells results in undesirable free carrier absorption, causing a tradeoff between series resistance and optical absorption losses in the infrared. A potential alternative is to replace the LCL with an epitaxial metal layer that would provide a low-resistance interconnect while not suffering from free carrier absorption. The internal metal layer would also serve as an efficient, panchromatic back surface reflector, providing the additional advantage of increased effective optical thickness of the InGaAs cell. In this paper, the authors present the first results on the growth and development of buried epitaxial metal layers for TPV applications. High quality, single crystal, epitaxial Fe{sub x}Al{sub 1{minus}x} layers were grown on InAlAs/InP substrates, having compositions in the range x = 0.40--0.80. Epitaxial metal layers up to 1,000 {angstrom} in thickness were achieved, with excellent uniformity over large areas and atomically smooth surfaces. X-ray diffraction studies indicate that all FeAl layers are strained with respect to the substrate, for the entire composition range studied and for all thicknesses. The FeAl layers exhibit excellent resistance characteristics, with resistivities from 60 {micro}ohm-cm to 100 {micro}ohm-cm, indicating that interface scattering has a negligible effect on lateral conductivity. Reflectance measurements show that the FeAl thickness must be at least 1,000 {angstrom} to achieve > 90% reflection in the infrared.

  5. Giant Up-Conversion Efficiency of InGaAs Quantum Dots in a Planar Microcavity

    PubMed Central

    Xu, Qinfeng; Piermarocchi, Carlo; Pershin, Yuriy V.; Salamo, G. J.; Xiao, Min; Wang, Xiaoyong; Shih, Chih-Kang

    2014-01-01

    Self-assembled InGaAs quantum dots (QDs) were fabricated inside a planar microcavity with two vertical cavity modes. This allowed us to excite the QDs coupled to one of the vertical cavity modes through two propagating cavity modes to study their down- and up-converted photoluminescence (PL). The up-converted PL increased continuously with the increasing temperature, reaching an intensity level comparable to that of the down-converted PL at ~120 K. This giant efficiency in the up-converted PL of InGaAs QDs was enhanced by about 2 orders of magnitude with respect to a similar structure without cavity. We tentatively explain the enhanced up-converted signal as a direct consequence of the modified spontaneous emission properties of the QDs in the microcavity, combined with the phonon absorption and emission effects. PMID:24492329

  6. Structural effects on heat dissipation in InGaAs MHEMTs

    NASA Astrophysics Data System (ADS)

    Noh, Jinhyun; Ryoo, Yeonmi; Jeon, Namcheol; Cha, Ho-Young; Seo, Kwang-Seok

    2013-04-01

    Since the high thermal resistance of InGaAs metamorphic high electron mobility transistors (MHEMTs) limits their applicability, thermal management should be taken into account when designing the device structure. In this study, structural effects on heat dissipation in InGaAs MHEMTs were carefully investigated and experimentally validated. With an air bridge thickness of 10 µm and a gate pitch distance of 24 µm, the maximum channel temperature in a flip-chip bonded device was noticeably reduced from 132 to 106 °C (i.e. corresponding thermal resistance from 252.17 to 178.14 K W-1). Improved heat dissipation with the proposed structure was experimentally validated using backside-mounted devices by an infrared temperature measurement method.

  7. Low-Cost InGaAs Detectors for Near-Infrared Imaging and Photometry

    NASA Astrophysics Data System (ADS)

    Sullivan, Peter; Croll, B.; Simcoe, R. A.

    2014-01-01

    Near-infrared detectors made from InGaAs should provide an alternative to HgCdTe that is particularly cost-effective for arrays of small telescopes or for covering large focal planes. Originally designed for night-vision equipment, these detectors can be suitable for astronomy if they support long, up-the-ramp exposures and are cooled sufficiently. We developed custom electronics to operate the FLIR APS640C detector in a camera with thermoelectric and chilled-water cooling. We achieved differential photometric precision of 500 ppm (0.5 mmag) hr^-1/2 observing J=7.7 stars with an effective telescope aperture of 0.25 m. Laboratory results from the latest generation of InGaAs detectors will be presented, and we discuss the limits to achieving background-limited performance in the Y, J, and H bands on 1 m - class telescopes.

  8. Uniform InGaAs quantum dot arrays fabricated using nanosphere lithography

    SciTech Connect

    Qian, X.; Li, J.; Wasserman, D.; Goodhue, W. D.

    2008-12-08

    We demonstrate the fabrication of optically active uniform InGaAs quantum dot arrays by combining nanosphere lithography and bromine ion-beam-assisted etching on a single InGaAs/GaAs quantum well. A wide range of lateral dot sizes was achieved from an oxygen plasma nanosphere resizing process. The increased lateral confinement of carriers in the dots results in low temperature photoluminescence blueshifts from 0.5 to 11 meV. Additional quantization was achieved using a selective wet-etch process. Our model suggests the presence of a 70 nm dead layer in the outer InGaAs radial edge, which we believe to be a result of defects and dislocations introduced during the dry-etch process.

  9. InGaAs HEMT MMIC LINA and doublers for EHF SATCOM ground terminals

    NASA Astrophysics Data System (ADS)

    Chow, P. D.; Lester, J.; Huang, P.; Jones, W.

    1991-07-01

    A K-band MMIC LNA and a family of MMIC frequency doublers were designed and fabricated using the planar-doped pseudomorphic InGaAs HEMT technology for future EHF satellite communication terminal transceiver applications. The InGaAs HEMT LNA showed less than 2 dB noise figure and more than 32 dB gain from 21 to 23 GHz. The Ku-, K-, and Q-band MMIC HEMT doublers demonstrated low conversion loss and wideband operation. They showed 10 dBm, 8 dBm, and 0 dBm output powers, and 2.5 dB, 4.5 dB, and 8.6 dB conversion losses at 17.4 GHz, 22.25 GHz, and 43.5 GHz, respectively.

  10. Electrical and Optical Performance Characteristics of p/n InGaAs Monolithic Interconnected Modules

    NASA Technical Reports Server (NTRS)

    Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Murray, Christopher S.; Riley, David R.

    1997-01-01

    There has been a traditional trade-off in ThermoPhotoVoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A Monolithic Interconnected Module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual Indium Gallium Arsenide (InGaAs) devices series-connected on a single semi-insulating Indium Phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An InfraRed (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74eV InGaAs, have demonstrated V(sub infinity) = 3.2 volts, J(sub sc) = 70 mA/sq cm and a fill factor of 66% under flashlamp testing. IR reflectance measurements (greater than 2 microns) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55 eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

  11. InGaAs focal plane array developments at III-V Lab

    NASA Astrophysics Data System (ADS)

    Rouvié, Anne; Reverchon, Jean-Luc; Huet, Odile; Djedidi, Anis; Robo, Jean-Alexandre; Truffer, Jean-Patrick; Bria, Toufiq; Pires, Mauricio; Decobert, Jean; Costard, Eric

    2012-06-01

    SWIR detection band benefits from natural (sun, night glow, thermal radiation) or artificial (eye safe lasers) photons sources combined to low atmospheric absorption and specific contrast compared to visible wavelengths. It gives the opportunity to address a large spectrum of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control). InGaAs material appears as a good candidate to satisfy SWIR detection needs. The lattice matching with InP constitutes a double advantage to this material: attractive production capacity and uncooled operation thanks to low dark current level induced by high quality material. For few years, III-VLab has been studying InGaAs imagery, gathering expertise in InGaAs material growth and imaging technology respectively from Alcatel-Lucent and Thales, its two mother companies. This work has lead to put quickly on the market a 320x256 InGaAs module, exhibiting high performances in terms of dark current, uniformity and quantum efficiency. In this paper, we present the last developments achieved in our laboratory, mainly focused on increasing the pixels number to VGA format associated to pixel pitch decrease (15μm) and broadening detection spectrum toward visible wavelengths. Depending on targeted applications, different Read Out Integrated Circuits (ROIC) have been used. Low noise ROIC have been developed by CEA LETI to fit the requirements of low light level imaging whereas logarithmic ROIC designed by NIT allows high dynamic imaging adapted for automotive safety.

  12. Growth, microstructure, and luminescent properties of direct-bandgap InAlP on relaxed InGaAs on GaAs substrates

    NASA Astrophysics Data System (ADS)

    Mukherjee, K.; Beaton, D. A.; Christian, T.; Jones, E. J.; Alberi, K.; Mascarenhas, A.; Bulsara, M. T.; Fitzgerald, E. A.

    2013-05-01

    Direct-bandgap InAlP alloy has the potential to be an active material in nitride-free yellow-green and amber optoelectronics with applications in solid-state lighting, display devices, and multi-junction solar cells. We report on the growth of high-quality direct-bandgap InAlP on relaxed InGaAs graded buffers with low threading dislocation densities. Structural characterization reveals phase-separated microstructures in these films which have an impact on the luminescence spectrum. While similar to InGaP in many ways, the greater tendency for phase separation in InAlP leads to the simultaneous occurrence of compositional inhomogeneity and CuPt-B ordering. Mechanisms connecting these two structural parameters are presented as well as results on the effect of silicon and zinc dopants on homogenizing the microstructure. Spontaneous formation of tilted planes of phase-separated material, with alternating degrees of ordering, is observed when InAlP is grown on vicinal substrates. The photoluminescence peak-widths of these films are actually narrower than those grown on exact (001) substrates. We find that, despite phase-separation, ordered direct-bandgap InAlP is a suitable material for optoelectronics.

  13. n/p/n Tunnel Junction InGaAs Monolithic Interconnected Module (MIM)

    NASA Technical Reports Server (NTRS)

    Wilt, David M.; Murray, Christopher S.; Fatemi, Navid S.; Weizer, Victor

    2005-01-01

    The Monolithic Interconnected Module (MIM), originally introduced at the First NREL thermophotovoltaic (TPV) conference, consists of low-bandgap indium gallium arsenide (InGaAs) photovoltaic devices, series interconnected on a common semi-insulating indium phosphide (inP) substrate. An infrared reflector is deposited on the back surface of the substrate to reflect photons, which were not absorbed in the first pass through the structure. The single largest optical loss in the current device occurs int he heavily doped p-type emitter. A new MIM design (pat.pend.) has been developed which flips the polarity of the conventional MIM cell (i.e., n/p rather than p/n), eliminating the need for the high conductivity p-type emitter. The p-type base of the cell is connected to the n-type lateral conduction layer through a thin InGaAs tunnel junction. 0.58 eV and 0.74 eV InGaAs devices have demonstrated reflectances above 90% for wavelengths beyond the bandgap (greater than 95% for unprocessed structures). Electrical measurements indicate minimal voltage drops across the tunnel junction (less than mV/junction under 1200K-blackbody illumnination) and fill factors that are above 70% at current densities (J(sub sc)) above 8 Angstroms per square centimeters for the 0.74eV devices.

  14. n/p/n tunnel junction InGaAs Monolithic Interconnected Module (MIM)

    SciTech Connect

    Wilt, D.M.; Murray, C.S.; Fatemi, N.S.; Weizer, V.

    1999-03-01

    The Monolithic Interconnected Module (MIM), originally introduced at the First NREL thermophotovoltaic (TPV) conference, consists of low-bandgap indium gallium arsenide (InGaAs) photovoltaic devices, series interconnected on a common semi-insulating indium phosphide (InP) substrate. An infrared reflector is deposited on the back surface of the substrate to reflect photons, which were not absorbed in the first pass through the structure. The single largest optical loss in the current device occurs in the heavily doped {ital p}-type emitter. A new MIM design (pat pend.) has been developed which flips the polarity of the conventional MIM cell (i.e., n/p rather than p/n), eliminating the need for the high conductivity {ital p}-type emitter. The {ital p}-type base of the cell is connected to the {ital n}-type lateral conduction layer through a thin InGaAs tunnel junction. 0.58 eV and 0.74 eV InGaAs devices have demonstrated reflectances above 90{percent} for wavelengths beyond the bandgap ({gt}95{percent} for unprocessed structures). Electrical measurements indicate minimal voltage drops across the tunnel junction ({lt}3 mV/junction under 1200 K-blackbody illumination) and fill factors that are above 70{percent} at current densities (J{sub sc}) above 8 A/cm{sup 2} for the 0.74 eV devices. {copyright} {ital 1999 American Institute of Physics.}

  15. InGaAs concentrator cells for laser power converters and tandem cells

    NASA Technical Reports Server (NTRS)

    Wojtczuk, S.; Vernon, S.; Gagnon, E.

    1993-01-01

    In(0.53)Ga(0.47)As N-on-P concentrator cells were made as part of an effort to develop 1.315 micron laser power converters. The 1.315 micron laser power conversion efficiency was estimated as 29.4 percent (at 5.57 W/cm(sup 2)) based on an 86 percent measured external quantum efficiency at 1.315 microns, and a measured open circuit voltage (484 mV), and fill-factor (67 percent) at the equivalent AM0 short-circuit photocurrent (5.07 A/cm(sup 2)). A 13.5 percent percent AMO efficiency was achieved at 89 suns and 25 C. Measured one-sun and 100-sun AMO efficiency, log I-V analysis, and quantum efficiency are presented for InGaAs cells with and without InP windows to passivate the front surface. Windowed cells performed better at concentration than windowless cells. Lattice mismatch between InGaAs epilayers and InP substrate was less than 800 ppm. Theoretical efficiency is estimated for 1.315 microns laser power converters versus the bandgap energy. Adding aluminum to InGaAs to form In(x)Al(y)Ga(1-x-y)As is presented as a way to achieve an optimal bandgap for 1.315 microns laser power conversion.

  16. Phase separation and ordering in InGaAs and InGaAs materials. Final report

    SciTech Connect

    Not Available

    1995-02-23

    This report highlights the advances in the understanding of phase separation and atomic ordering in mixed III-V layers. Specifically, the following issues were addressed in the grant period (August 1987 to February 1992): (1) bulk vs surface phase separation; (2) influence of growth technique on phase separation; (3) origin of coarse contrast modulations; (4) influence of dopant diffusion on phase separated microstructures; (5) influence of annealing on carrier mobility in InGaAsP layers; (6) co-existence of CuPt-type ordering and phase separation; (7) influence of growth conditions on ordering; (8) influence of surface reconstruction on atomic ordering.

  17. In(Ga)As quantum dot formation on group-III assisted catalyst-free InGaAs nanowires.

    PubMed

    Heiss, Martin; Ketterer, Bernt; Uccelli, Emanuele; Morante, Joan Ramon; Arbiol, Jordi; Fontcuberta i Morral, Anna

    2011-05-13

    Growth of GaAs and In(x)Ga(1-x)As nanowires by the group-III assisted molecular beam epitaxy growth method on (001)GaAs/SiO(2) substrates is studied in dependence on growth temperature, with the objective of maximizing the indium incorporation. Nanowire growth was achieved for growth temperatures as low as 550 °C. The incorporation of indium was studied by low temperature micro-photoluminescence spectroscopy, Raman spectroscopy and electron energy loss spectroscopy. The results show that the incorporation of indium achieved by lowering the growth temperature does not have the effect of increasing the indium concentration in the bulk of the nanowire, which is limited to 3-5%. For growth temperatures below 575 °C, indium rich regions form at the surface of the nanowires as a consequence of the radial growth. This results in the formation of quantum dots, which exhibit spectrally narrow luminescence. PMID:21430322

  18. The physical origin of dispersion in accumulation in InGaAs based metal oxide semiconductor gate stacks

    NASA Astrophysics Data System (ADS)

    Krylov, Igor; Ritter, Dan; Eizenberg, Moshe

    2015-05-01

    Dispersion in accumulation is a widely observed phenomenon in technologically important InGaAs gate stacks. Two principal different interface defects were proposed as the physical origin of this phenomenon—disorder induced gap states and border traps. While the gap states are located at the semiconductor side of the interface, the border traps are related to the dielectric side. The study of Al2O3, HfO2, and an intermediate composition of HfxAlyO deposited on InGaAs enabled us to find a correlation between the dispersion and the dielectric/InGaAs band offset. At the same time, no change in the dispersion was observed after applying an effective pre-deposition treatment which results in significant reduction of the interface states. Both observations prove that border traps are the physical origin of the dispersion in accumulation in InGaAs based metal-oxide-semiconductor gate stacks.

  19. Precision of a Low-Cost InGaAs Detector for Near Infrared Photometry

    NASA Astrophysics Data System (ADS)

    Sullivan, Peter W.; Croll, Bryce; Simcoe, Robert A.

    2013-09-01

    We have designed, constructed, and tested an InGaAs near-infrared camera to explore whether low-cost detectors can make small (<= 1 m) telescopes capable of precise (< 1 mmag) infrared photometry of relatively bright targets. The camera is constructed around the 640 × 512 pixel APS640C sensor built by FLIR Electro-Optical Components. We designed custom analog-to-digital electronics for maximum stability and minimum noise. The InGaAs dark current halves with every 7°C of cooling, and we reduce it to 840 e- s-1 pixel-1 (with a pixel-to-pixel variation of ± 200 e- s-1 pixel-1) by cooling the array to -20°C. Beyond this point, glow from the readout dominates. The single-sample read noise of 149 e- is reduced to 54 e- through up-the-ramp sampling. Laboratory testing with a star field generated by a lenslet array shows that two-star differential photometry is possible to a precision of 631 ± 205 ppm (0.68 mmag) hr-1/2 at a flux of 2.4 × 104 e- s-1. Employing three comparison stars and decorrelating reference signals further improves the precision to 483 ± 161 ppm (0.52 mmag) hr-1/2. Photometric observations of HD80606 and HD80607 (J = 7.7 and 7.8) in the Y band shows that differential photometry to a precision of 415 ppm (0.45 mmag) hr-1/2 is achieved with an effective telescope aperture of 0.25 m. Next-generation InGaAs detectors should indeed enable Poisson-limited photometry of brighter dwarfs with particular advantage for late-M and L types. In addition, one might acquire near-infrared photometry simultaneously with optical photometry or radial velocity measurements to maximize the return of exoplanet searches with small telescopes.

  20. InGaAs versus HgCdTe for short-wavelength infrared applications

    NASA Astrophysics Data System (ADS)

    Rogalski, Antoni; Ciupa, Robert

    1999-04-01

    The carrier lifetimes in In(subscript x)Ga(subscript 1-x)As (InGaAs) and Hg(subscript 1-x)Cd(subscript x)Te (HgCdTe) ternary alloys for radiative and Auger recombination are calculated for temperature 300 K in the short wavelength range 1.5 less than (lambda) less than 3.7 micrometer. Due to photon recycling, an order of magnitude enhancements in the radiative lifetimes over those obtained from the standard van Roosbroeck and Shockley expression, has been assumed. This theoretical prediction has been confirmed by good agreement with experimental data for n-type In(subscript 0.53)Ga(subscript 0.47)As. The possible Auger recombination mechanisms (CHCC, CHLH and CHSH processes) in direct-gap semiconductors are investigated. In both n-type ternary alloys, the carrier lifetimes are similar, and competition between radiative and CHCC processes take place. In p-type materials the carrier lifetime are also comparable, however the most effective channels of Auger mechanisms are: CHSH process in InGaAs, and CHLH process in HgCdTe. Next, the performance of heterostructure p-on-n photovoltaic devices are considered. Theoretically predicted R(subscript o)A values are compared with experimental data reported by other authors. In(subscript 0.53)Ga(subscript 0.47)As photodiodes have shown the device performance within a factor of 10 of theoretical limit. However, the performance of InGaAs photodiodes decreases rapidly at intermediate wavelengths due to mismatch-induced defects. HgCdTe photodiodes maintain high performance close to ultimate limit over a wider range of wavelengths. In this context technology of HgCdTe is considerably advanced since the same lattice parameter of this alloy over wide composition range.

  1. InGaAs quantum dot molecules around self-assembled GaAs nanomound templates

    SciTech Connect

    Lee, J. H.; Wang, Zh. M.; Strom, N. W.; Mazur, Yu. I.; Salamo, G. J.

    2006-11-13

    Several distinctive self-assembled InGaAs quantum dot molecules (QDMs) are studied. The QDMs self-assemble around nanoscale-sized GaAs moundlike templates fabricated by droplet homoepitaxy. Depending on the specific InAs monolayer coverage, the number of QDs per GaAs mound ranges from two to six (bi-QDMs to hexa-QDMs). The Ga contribution from the mounds is analyzed in determining the morphologies of the QDMs, with respect to the InAs coverages ranging between 0.8 and 2.4 ML. Optical characterization shows that the resulting nanostructures are high-quality nanocrystals.

  2. Investigation of cross-hatch surface and study of anisotropic relaxation and dislocation on InGaAs on GaAs (001)

    NASA Astrophysics Data System (ADS)

    Kumar, Rahul; Bag, Ankush; Mukhopadhyay, Partha; Das, Subhashis; Biswas, Dhrubes

    2016-05-01

    There exist discrepancies between reports on cross-hatch (CH) behaviour and its interaction with interfacial misfit dislocations in the literature. In this work, a thorough CH analysis has been presented by use of conventional and statistical analysis of AFM data. It has been shown that correlation between cross-hatch and misfit dislocation depends on the growth conditions and residual strain. Anisotropic relaxation and dislocations, composition and epitaxial tilt have been studied by HRXRD analysis. To illustrate these findings, molecular beam epitaxy (MBE) grown metamorphic InGaAs on GaAs (001) samples have been used. Reciprocal space mapping has been used to characterize the composition and relaxation while epilayer tilt and dislocation have been investigated by HRXRD rocking curve. A better understanding of CH pattern can enable us to minimize the surface roughness for metamorphic electronic devices and to fully utilize the quasi-periodic undulation in cross-hatch in applications, like ordered quantum dot growth. [Figure not available: see fulltext.

  3. Extremely low nonalloyed and alloyed contact resistance using an InAs cap layer on InGaAs by molecular-beam epitaxy

    NASA Technical Reports Server (NTRS)

    Peng, C. K.; Chen, J.; Chyi, J.; Morkoc, H.

    1988-01-01

    Extremely low alloyed and nonalloyed ohmic contact resistances have been formed on n-type InAs/In(0.53)Ga(0.47)As/In(0.52)Al(0.48)As structures grown on InP(Fe) by molecular-beam epitaxy. To insure the accuracy of the small contact resistances measured, an extended transmission line model was used to extrapolate contact resistances from test patterns with multiple gap spacings varying from 1 to 20 microns. For a 150-A-thick InAs layer doped to 2 x 10 to the 18th/cu cm and a 0.1-micron-thick InGaAs layer doped to 1 x 10 to the 18th/cu cm, a specific contact resistance of 2.6 x 10 to the -8th ohm-asterisk sq cm was measured for the nonalloyed contact, while a resistance less than 1.7 x 10 to the -8th ohm-asterisk sq cm is reported for the alloyed contact. Conventional Au-Ge/Ni/Au was used for the ohmic metal contact and alloying was performed at 500 C for 50 s in flowing H2. Using a thermionic field emission model, the barrier height at the InAs/InGaAs interface was calculated to be 20 meV.

  4. ROTARY BULK SOLIDS DIVIDER

    DOEpatents

    Maronde, Carl P.; Killmeyer JR., Richard P.

    1992-03-03

    An apparatus for the disbursement of a bulk solid sample comprising, a gravity hopper having a top open end and a bottom discharge end, a feeder positioned beneath the gravity hopper so as to receive a bulk solid sample flowing from the bottom discharge end, and a conveyor receiving the bulk solid sample from the feeder and rotating on an axis that allows the bulk solid sample to disperse the sample to a collection station.

  5. Rotary bulk solids divider

    DOEpatents

    Maronde, Carl P.; Killmeyer, Jr., Richard P.

    1992-01-01

    An apparatus for the disbursement of a bulk solid sample comprising, a gravity hopper having a top open end and a bottom discharge end, a feeder positioned beneath the gravity hopper so as to receive a bulk solid sample flowing from the bottom discharge end, and a conveyor receiving the bulk solid sample from the feeder and rotating on an axis that allows the bulk solid sample to disperse the sample to a collection station.

  6. Bulk Fuel Man.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    This student guide, one of a series of correspondence training courses designed to improve the job performance of members of the Marine Corps, deals with the skills needed by bulk fuel workers. Addressed in the four individual units of the course are the following topics: bulk fuel equipment, bulk fuel systems, procedures for handling fuels, and…

  7. Near-infrared InGaAs detectors for background-limited imaging and photometry

    NASA Astrophysics Data System (ADS)

    Sullivan, Peter W.; Croll, Bryce; Simcoe, Robert A.

    2014-07-01

    Originally designed for night-vision equipment, InGaAs detectors are beginning to achieve background-limited performance in broadband imaging from the ground. The lower cost of these detectors can enable multi-band instruments, arrays of small telescopes, and large focal planes that would be uneconomical with high-performance HgCdTe detectors. We developed a camera to operate the FLIR AP1121 sensor using deep thermoelectric cooling and up-the-ramp sampling to minimize noise. We measured a dark current of 163 e- s-1 pix-1, a read noise of 87 e- up-the-ramp, and a well depth of 80k e-. Laboratory photometric testing achieved a stability of 230 ppm hr-1/2, which would be required for detecting exoplanet transits. InGaAs detectors are also applicable to other branches of near-infrared time-domain astronomy, ranging from brown dwarf weather to gravitational wave follow-up.

  8. Logarithmic InGaAs detectors with global shutter and active dark current reduction

    NASA Astrophysics Data System (ADS)

    Ni, Yang; Arion, Bogdan; Bouvier, Christian; Noguier, Vincent

    2015-05-01

    In this paper, we present newly developed logarithmic InGaAs detectors with global shuttering and also an active dark current reduction technique to ensure ambient temperature operation without TEC for industrial applications. The newly released detectors come with both VGA (15um pitch) and QVGA (25um pitch) resolutions, giving the possibility to use lens less than 1-inch size. The logarithmic response is obtained by using solar-cell mode InGaAs photodiodes. The VGA and QVGA ROICs have 3 analog memories inside each pixel which permit, except the classic ITR, IWR and CDS modes, a new differential imaging mode which can be a useful feature in active imaging systems. The photodiode frontend circuit, in pure voltage mode, is made with non-inverting amplifier instead of CTIA. The reason of this choice is that the exposure time can be shortened without need of excessive power consumption as in CTIA front-end. We think that this arrangement associated with true CDS could match the noise performance of CTIA based one. VGA and QVGA ROICs have been designed and manufactured by using 0.18um 1P4M CMOS process. Both ROIC have been tested with success and match the design targets. The first batch of both detectors is under fabrication and will be presented during the conference.

  9. Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

    NASA Astrophysics Data System (ADS)

    Bulutay, Ceyhun; Chekhovich, E. A.; Tartakovskii, A. I.

    2014-11-01

    A wealth of atomistic information is contained within a self-assembled quantum dot (QD), associated with its chemical composition and the growth history. In the presence of quadrupolar nuclei, as in InGaAs QDs, much of this is inherited to nuclear spins via the coupling between the strain within the polar lattice and the electric quadrupole moments of the nuclei. Here, we present a computational study of the recently introduced inverse spectra nuclear magnetic resonance technique to assess its suitability for extracting such structural information. We observe marked spectral differences between the compound InAs and alloy InGaAs QDs. These are linked to the local biaxial and shear strains, and the local bonding configurations. The cation alloying plays a crucial role especially for the arsenic nuclei. The isotopic line profiles also largely differ among nuclear species: While the central transition of the gallium isotopes have a narrow linewidth, those of arsenic and indium are much broader and oppositely skewed with respect to each other. The statistical distributions of electric field gradient (EFG) parameters of the nuclei within the QD are analyzed. The consequences of various EFG axial orientation characteristics are discussed. Finally, the possibility of suppressing the first-order quadrupolar shifts is demonstrated by simply tilting the sample with respect to the static magnetic field.

  10. Multifunction InGaAs detector with on-chip signal processing

    NASA Astrophysics Data System (ADS)

    Shkedy, Lior; Fraenkel, Rami; Fishman, Tal; Giladi, Avihoo; Bykov, Leonid; Grimberg, Ilana; Ilan, Elad; Vaserman, Shay; Koifman, Alina

    2013-06-01

    Advanced electro-optical systems are designed towards a more compact, low power, and low cost solution with respect to traditional systems. Integration of several components or functionalities, such as infrared imager, laser designator, laser range finder (LRF), into one multi-function detector serves this trend. SNIR Read-Out Integrated Circuit (ROIC) incorporates this high level of signal processing and with relatively low power consumption. In this paper we present measurement results from a Focal Plane Array (FPA) where the SNIR ROIC is Flip-Chip bonded to a 15µm pitch VGA InGaAs detector array. The FPA is integrated into a metallic vacuum sealed package. We present InGaAs arrays with dark current density below 1.5 nA/cm2 at 280K (typically 1fA), Quantum Efficiency higher than 80% at 1550 nm and operability better than 99.5%. The metallic package is integrated with a low power proximity electronics which delivers Camera Link output. The overall power dissipation is less than 1W, not including Thermal-Electric Cooling (TEC), which is required in some applications. The various active and passive operation modes of this detector will be reviewed. Specifically, we concentrate on the "high gain" mode with low readout noise for Low Light Level imaging application. Another promising feature is the Asynchronous Laser Pulse Detection (ALPD) with remarkably low detection thresholds.

  11. Impact of atomic layer deposition temperature on HfO2/InGaAs metal-oxide-semiconductor interface properties

    NASA Astrophysics Data System (ADS)

    Suzuki, Rena; Taoka, Noriyuki; Yokoyama, Masafumi; Kim, Sang-Hyeon; Hoshii, Takuya; Maeda, Tatsuro; Yasuda, Tetsuji; Ichikawa, Osamu; Fukuhara, Noboru; Hata, Masahiko; Takenaka, Mitsuru; Takagi, Shinichi

    2012-10-01

    We have studied the impact of atomic-layer-deposition (ALD) temperature on the HfO2/InGaAs metal-oxide-semiconductor (MOS) interface with a comparison to the Al2O3/InGaAs interface. It is found that the interface properties such as the C-V characteristics and the interface trap density (Dit) and the interface structure of HfO2/InGaAs have strong dependence on the ALD temperature, while the Al2O3/InGaAs interfaces hardly depend on it. As a result, we have achieved the HfO2/InGaAs interfaces with low Dit comparable to that in the Al2O3/InGaAs interface by lowering the ALD temperature down to 200 °C or less. Also, we have found that As2O3 and Ga2O3 formed at the interface during ALD increase with a decrease in the ALD temperature. Combined with the ALD temperature dependence of the electrical characteristics, the better C-V characteristics and the lower Dit obtained at the lower ALD temperature can be explained by the As2O3 and Ga2O3 passivation of the HfO2/InGaAs interfaces, which is consistent with a reported theoretical result on the effective passivation of III-V MOS interfaces by trivalent oxides.

  12. Buffer Layer Effects on Tandem InGaAs TPV Devices

    NASA Technical Reports Server (NTRS)

    Wilt, David M.; Wehrer, Rebecca J.; Maurer, William F.

    2004-01-01

    Single junction indium gallium arsenide (InGaAs) based TPV devices have demonstrated efficiencies in excess of 20% at radiator temperatures of 1058 C. Modeling suggests that efficiency improvements in single bandgap devices should continue although they will eventually plateau. One approach for extending efficiencies beyond the single bandgap limit is to follow the technique taken in the solar cell field, namely tandem TPV cells. Tandem photovoltaic devices are traditionally composed of cells of decreasing bandgap, connected electrically and optically in series. The incident light impinges upon the highest bandgap first. This device acts as a sieve, absorbing the high-energy photons, while allowing the remainder to pass through to the underlying cell(s), and so on. Tandem devices reduce the energy lost to overexcitation as well as reducing the current density (Jsc). Reduced Jsc results in lower resistive losses and enables the use of thinner and lower doped lateral current conducting layers as well as a higher pitch grid design. Fabricating TPV tandem devices utilizing InGaAs for all of the component cells in a two cell tandem necessitates the inclusion of a buffer layer in-between the high bandgap device (In0.53 Ga0.47As - 0.74eV) and the low bandgap device (In0.66Ga0.34As - 0.63eV) to accommodate the approximately 1% lattice strain generated due to the change in InGaAs composition. To incorporate only a single buffer layer structure, we have investigated the use of the indium phosphide (InP) substrate as a superstrate. Thus the high-bandgap, lattice- matched device is deposited first, followed by the buffer structure and the low-bandgap cell. The near perfect transparency of the high bandgap (1.35eV) iron-doped InP permits the device to be oriented such that the light enters through the substrate. In this paper we examine the impact of the buffer layer on the underlying lattice-matched InGaAs device. 0.74eV InGaAs devices were produced in a variety of

  13. 19 CFR 149.4 - Bulk and break bulk cargo.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

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  14. 19 CFR 149.4 - Bulk and break bulk cargo.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 2 2012-04-01 2012-04-01 false Bulk and break bulk cargo. 149.4 Section 149.4... TREASURY (CONTINUED) IMPORTER SECURITY FILING § 149.4 Bulk and break bulk cargo. (a) Bulk cargo exempted.... (b) Break bulk cargo exempted from time requirement. For break bulk cargo that is exempt from...

  15. 19 CFR 149.4 - Bulk and break bulk cargo.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 2 2014-04-01 2014-04-01 false Bulk and break bulk cargo. 149.4 Section 149.4... TREASURY (CONTINUED) IMPORTER SECURITY FILING § 149.4 Bulk and break bulk cargo. (a) Bulk cargo exempted.... (b) Break bulk cargo exempted from time requirement. For break bulk cargo that is exempt from...

  16. 19 CFR 149.4 - Bulk and break bulk cargo.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 2 2011-04-01 2011-04-01 false Bulk and break bulk cargo. 149.4 Section 149.4... TREASURY (CONTINUED) IMPORTER SECURITY FILING § 149.4 Bulk and break bulk cargo. (a) Bulk cargo exempted.... (b) Break bulk cargo exempted from time requirement. For break bulk cargo that is exempt from...

  17. 19 CFR 149.4 - Bulk and break bulk cargo.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 2 2013-04-01 2013-04-01 false Bulk and break bulk cargo. 149.4 Section 149.4... TREASURY (CONTINUED) IMPORTER SECURITY FILING § 149.4 Bulk and break bulk cargo. (a) Bulk cargo exempted.... (b) Break bulk cargo exempted from time requirement. For break bulk cargo that is exempt from...

  18. A low noise high readout speed 512×128 ROIC for shortwave InGaAs FPA

    NASA Astrophysics Data System (ADS)

    Huang, SongLei; Huang, Zhangcheng; Chen, Yu; Tang, Hengjing; Fang, Jiaxiong

    2015-03-01

    A low noise high readout speed 512×128 readout Integrated circuit (ROIC) based on capacitance trans-impedance amplifier (CTIA) is designed in this paper. The ROIC is flip-chip bonded with Indium bumps to InGaAs detectors which cutoff wavelength is 1.7μm, as a hybrid structure (InGaAs FPA). The ROIC with 30μm pixel pitch and 50fF integrated capacitance, is fabricated in 0.5μm DPTM CMOS process. The results show that output noise is about 3.0E-4V which equivalent readout noise is 95e-, output voltage swing is better than 2.5V; the dynamic range of InGaAs FPA reaches 69.7dB@2ms, and the power dissipation is about 175mw. The peak detectivity of InGaAs FPA reaches 2E12cmHz1/2w-1 at 300K without TEC cooling.

  19. Effects of buffer layer and back-surface field on MBE-grown InGaAsP/InGaAs solar cells

    NASA Astrophysics Data System (ADS)

    Wu, Yuanyuan; Ji, Lian; Dai, Pai; Tan, Ming; Lu, Shulong; Yang, Hui

    2016-02-01

    Solid-state molecular beam epitaxy (MBE)-grown InGaAsP/InGaAs dual-junction solar cells on InP substrates are reported. An efficiency of 10.6% under 1-sun AM1.5 global light intensity is realized for the dual-junction solar cell, while the efficiencies of 16.4 and 12.3% are reached for the top InGaAsP and bottom InGaAs cells, respectively. The effects of the buffer layer and back-surface field on the performance of solar cells are discussed. High device performance is achieved in the case of a low concentration of oxygen and weak recombination when InGaAs buffers and InP back-surface field layers are used, respectively.

  20. Short wave infrared InGaAs focal plane arrays detector: the performance optimization of photosensitive element

    NASA Astrophysics Data System (ADS)

    Gao, Xin-jiang; Tang, Zun-lie; Zhang, Xiu-chuan; Chen, Yang; Jiang, Li-qun; Cheng, Hong-bing

    2009-07-01

    Significant progress has been achieved in technology of the InGaAs focal plane arrays (FPA) detector operating in short wave infrared (SWIR) last two decades. The no cryogenic cooling, low manufacturing cost, low power, high sensitivity and maneuverability features inherent of InGaAs FPA make it as a mainstream SWIR FPA in a variety of critical military, national security, aerospace, telecommunications and industrial applications. These various types of passive image sensing or active illumination image detecting systems included range-gated imaging, 3-Dimensional Ladar, covert surveillance, pulsed laser beam profiling, machine vision, semiconductor inspection, free space optical communications beam tracker, hyperspectroscopy imaging and many others. In this paper the status and perspectives of hybrid InGaAs FPA which is composed of detector array (PDA) and CMOS readout integrate circuit (ROIC) are reviewed briefly. For various low light levels applications such as starlight or night sky illumination, we have made use of the interface circuit of capacitive feedback transimpedance amplifier (CTIA) in which the integration capacitor was adjustable, therefore implements of the physical and electrical characteristics matches between detector arrays and readout intergrate circuit was achieved excellently. Taking into account the influences of InGaAs detector arrays' optoelectronic characteristics on performance of the FPA, we discussed the key parameters of the photodiode in detailed, and the tradeoff between the responsivity, dark current, impedance at zero bias and junction capacitance of photosensitive element has been made to root out the impact factors. As a result of the educed approach of the photodiode's characteristics optimizing which involve with InGaAs PDA design and process, a high performance InGaAs FPA of 30um pixel pitch and 320×256 format has been developed of which the response spectrum range over 0.9um to 1.7um, the mean peak detectivity (λ=1.55

  1. Impact of La{sub 2}O{sub 3} interfacial layers on InGaAs metal-oxide-semiconductor interface properties in Al{sub 2}O{sub 3}/La{sub 2}O{sub 3}/InGaAs gate stacks deposited by atomic-layer-deposition

    SciTech Connect

    Chang, C.-Y. Takenaka, M.; Takagi, S.; Ichikawa, O.; Osada, T.; Hata, M.; Yamada, H.

    2015-08-28

    We examine the electrical properties of atomic layer deposition (ALD) La{sub 2}O{sub 3}/InGaAs and Al{sub 2}O{sub 3}/La{sub 2}O{sub 3}/InGaAs metal-oxide-semiconductor (MOS) capacitors. It is found that the thick ALD La{sub 2}O{sub 3}/InGaAs interface provides low interface state density (D{sub it}) with the minimum value of ∼3 × 10{sup 11} cm{sup −2} eV{sup −1}, which is attributable to the excellent La{sub 2}O{sub 3} passivation effect for InGaAs surfaces. It is observed, on the other hand, that there are a large amount of slow traps and border traps in La{sub 2}O{sub 3}. In order to simultaneously satisfy low D{sub it} and small hysteresis, the effectiveness of Al{sub 2}O{sub 3}/La{sub 2}O{sub 3}/InGaAs gate stacks with ultrathin La{sub 2}O{sub 3} interfacial layers is in addition evaluated. The reduction of the La{sub 2}O{sub 3} thickness to 0.4 nm in Al{sub 2}O{sub 3}/La{sub 2}O{sub 3}/InGaAs gate stacks leads to the decrease in hysteresis. On the other hand, D{sub it} of the Al{sub 2}O{sub 3}/La{sub 2}O{sub 3}/InGaAs interfaces becomes higher than that of the La{sub 2}O{sub 3}/InGaAs ones, attributable to the diffusion of Al{sub 2}O{sub 3} through La{sub 2}O{sub 3} into InGaAs and resulting modification of the La{sub 2}O{sub 3}/InGaAs interface structure. As a result of the effective passivation effect of La{sub 2}O{sub 3} on InGaAs, however, the Al{sub 2}O{sub 3}/10 cycle (0.4 nm) La{sub 2}O{sub 3}/InGaAs gate stacks can realize still lower D{sub it} with maintaining small hysteresis and low leakage current than the conventional Al{sub 2}O{sub 3}/InGaAs MOS interfaces.

  2. Carrier dynamics in InGaAs with embedded ErAs nanoislands

    SciTech Connect

    Azad, Abul K.; Prasankumar, Rohit P.; Talbayev, Diyar; Taylor, Antoinette J.; O'Hara, John F.; Averitt, Richard D.; Zide, Joshua M. O.; Lu Hong; Gossard, Arthur C.

    2008-09-22

    Using time-resolved optical-pump terahertz-probe spectroscopy, we study the ultrafast carrier dynamics in In{sub 0.53}Ga{sub 0.47}As:ErAs, a potential candidate for 1550 nm based terahertz photoconductive detectors. Material growth is performed by codepositing ErAs nanoislands with Be-compensated InGaAs on an InP:Fe substrate using molecular beam epitaxy. The material shows a rapid photoconductivity response following optical excitation. Photoexcitation with {approx}0.5 {mu}J/cm{sup 2} 800 nm femtosecond laser pulses yields a 3.2 ps carrier lifetime in optical-pump terahertz-probe experiments. We also measure the carrier lifetime using a 1550 nm femtosecond optical pump-probe system, and it is found to agree well with the terahertz measurements. These short lifetimes demonstrate significant potential for implementing terahertz systems using telecommunication based technologies.

  3. Polariton condensation in a strain-compensated planar microcavity with InGaAs quantum wells

    SciTech Connect

    Cilibrizzi, Pasquale; Askitopoulos, Alexis Silva, Matteo; Lagoudakis, Pavlos G.; Bastiman, Faebian; Clarke, Edmund; Zajac, Joanna M.; Langbein, Wolfgang

    2014-11-10

    The investigation of intrinsic interactions in polariton condensates is currently limited by the photonic disorder of semiconductor microcavity structures. Here, we use a strain compensated planar GaAs/AlAs{sub 0.98}P{sub 0.02} microcavity with embedded InGaAs quantum wells having a reduced cross-hatch disorder to overcome this issue. Using real and reciprocal space spectroscopic imaging under non-resonant optical excitation, we observe polariton condensation and a second threshold marking the onset of photon lasing, i.e., the transition from the strong to the weak-coupling regime. Condensation in a structure with suppressed photonic disorder is a necessary step towards the implementation of periodic lattices of interacting condensates, providing a platform for on chip quantum simulations.

  4. InGaAs spin light emitting diodes measured in the Faraday and oblique Hanle geometries

    NASA Astrophysics Data System (ADS)

    Mansell, R.; Laloë, J.-B.; Holmes, S. N.; Petrou, A.; Farrer, I.; Jones, G. A. C.; Ritchie, D. A.; Barnes, C. H. W.

    2016-04-01

    InGaAs quantum well light emitting diodes (LED) with spin-injecting, epitaxial Fe contacts were fabricated using an in situ wafer transfer process where the semiconductor wafer was transferred under ultrahigh vacuum (UHV) conditions to a metals growth chamber to achieve a high quality interface between the two materials. The spin LED devices were measured optically with applied magnetic fields in either the Faraday or the oblique Hanle geometries in two experimental set-ups. Optical polarizations efficiencies of 4.5% in the Faraday geometry and 1.5% in the Hanle geometry are shown to be equivalent. The polarization efficiency of the electroluminescence is seen to decay as the temperature increases although the spin lifetime remains constant due to the influence of the D’yakonov–Perel’ spin scattering mechanism in the quantum well.

  5. InGaAs PV Device Development for TPV Power Systems

    NASA Technical Reports Server (NTRS)

    Wilt, David M.; Fatemi, Navid S.; Hoffman, Richard W., Jr.; Jenkins, Phillip P.; Scheiman, David; Lowe, Roland; Landis, Geoffrey A.

    1994-01-01

    Indium gallium arsenide (InGaAs) photovoltaic devices have been fabricated with bandgaps ranging from 0.75 eV to 0.60 eV on Indium Phosphide (InP) substrates. Reported efficiencies have been as high as 11.2 percent (AMO) for the lattice matched 0.75 eV devices. The 0.75 eV cell demonstrated 14.8 percent efficiency under a 1500 K blackbody with a projected efficiency of 29.3 percent. The lattice mismatched devices (0.66 and 0.60 eV) demonstrated measured efficiencies of 8 percent and 6 percent respectively under similar conditions. Low long wavelength response and high dark currents are responsible for the poor performance of the mismatched devices. Temperature coefficients have been measured and are presented for all of the bandgaps tested.

  6. InGaAs PV device development for TPV power systems

    SciTech Connect

    Wilt, D.M.; Fatemi, N.S.; Hoffman, R.W. Jr.; Jenkins, P.P.; Brinker, D.J.; Scheiman, D.; Lowe, R.A.; Chubb, D.

    1994-09-01

    Indium gallium arsenide (InGaAs) photovoltaic devices have been fabricated with bandgaps ranging from 0.75 eV to 0.60 on Indium phosphide (InP) substrates. Reported efficiencies have been as high as 11.2 percent (AMO) for the lattice matched 0.75 eV devices. The 0.75 eV cell demonstrated 14.8 percent efficiency under a 1500 K blackbody with a projected efficiency of 29.3 percent. The lattice mismatched devices (0.66 and 0.60 eV) demonstrated measured efficiencies of 8 percent and 6 percent respectively under similar conditions. Low long wavelength response and high rack currents are responsible for the poor performance of the mismatched devices. Temperature coefficients have been measured and are presented for all of the bandgaps tested.

  7. InGaAs PV device development for TPV power systems

    SciTech Connect

    Wilt, D.M.; Fatemi, N.S.; Hoffman, R.W. Jr.; Jenkins, P.P.; Scheiman, D.; Lowe, R.; Landis, G.A.

    1994-08-01

    Indium gallium arsenide (InGaAs) photovoltaic devices have been fabricated with bandgaps ranging from 0.75 eV to 0.60 eV on Indium Phosphide (InP) substrates. Reported efficiencies have been as high as 11.2 percent (AMO) for the lattice matched 0.75 eV devices. The 0.75 eV cell demonstrated 14.8 percent efficiency under a 1500 K blackbody with a projected efficiency of 29.3 percent. The lattice mismatched devices (0.66 and 0.60 eV) demonstrated measured efficiencies of 8 percent and 6 percent respectively under similar conditions. Low long wavelength response and high dark currents are responsible for the poor performance of the mismatched devices. Temperature coefficients have been measured and are presented for all of the bandgaps tested.

  8. InGaAs PV device development for TPV power systems

    SciTech Connect

    Wilt, D.M.; Fatemi, S.; Hoffman, R.W. Jr.; Jenkins, P.P.; Scheiman, D.; Lowe, R.; Landis, G.A.

    1995-01-05

    Indium Gallium Arsenide (InGaAs) photovoltaic devices have been fabricated with bandgaps ranging from 0.75 eV to 0.60 eV on Indium Phosphide (InP) substrates. Reported efficiencies have been as high as 11.2% (AM0) for the lattice matched 0.75 eV devices. The 0.75 eV cell demonstrated 14.8% efficiency under a 1500 {degree}K blackbody with a projected efficiency of 29.3%. The lattice mismatched devices (0.66 and 0.60 eV) demonstrated measured efficiencies of 8% and 6% respectively under similar conditions. Low long wavelength response and high dark currents are responsible for the poor performance of the mismatched devices. Temperature coefficients have been measured and are presented for all of the bandgaps tested. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  9. Measurement of heavy-hole spin dephasing in (InGa)As quantum dots

    NASA Astrophysics Data System (ADS)

    Dahbashi, R.; Hübner, J.; Berski, F.; Wiegand, J.; Marie, X.; Pierz, K.; Schumacher, H. W.; Oestreich, M.

    2012-01-01

    We measure the spin dephasing of holes localized in self-assembled (InGa)As quantum dots by spin noise spectroscopy. The localized holes show a distinct hyperfine interaction with the nuclear spin bath despite the p-type symmetry of the valence band states. The experiments reveal a short spin relaxation time τfasthh of 27 ns and a second, long spin relaxation time τslowhh which exceeds the latter by more than one order of magnitude. The two times are attributed to heavy-hole spins aligned perpendicular and parallel to the stochastic nuclear magnetic field. Intensity dependent measurements and numerical simulations reveal that the long relaxation time is still obscured by light absorption, despite low laser intensity and large detuning. Off-resonant light absorption causes a suppression of the spin noise signal due to the creation of a second hole entailing a vanishing hole spin polarization.

  10. InGaAs PV device development for TPV power systems

    NASA Technical Reports Server (NTRS)

    Wilt, David M.; Fatemi, Navid S.; Hoffman, Richard W., Jr.; Jenkins, Phillip P.; Brinker, David J.; Scheiman, David; Lowe, Roland A.; Chubb, Donald

    1994-01-01

    Indium gallium arsenide (InGaAs) photovoltaic devices have been fabricated with bandgaps ranging from 0.75 eV to 0.60 on Indium phosphide (InP) substrates. Reported efficiencies have been as high as 11.2 percent (AMO) for the lattice matched 0.75 eV devices. The 0.75 eV cell demonstrated 14.8 percent efficiency under a 1500 K blackbody with a projected efficiency of 29.3 percent. The lattice mismatched devices (0.66 and 0.60 eV) demonstrated measured efficiencies of 8 percent and 6 percent respectively under similar conditions. Low long wavelength response and high rack currents are responsible for the poor performance of the mismatched devices. Temperature coefficients have been measured and are presented for all of the bandgaps tested.

  11. Dynamic vibronic coupling in InGaAs quantum dots [Invited

    NASA Astrophysics Data System (ADS)

    Brash, A. J.; Martins, L. M. P. P.; Barth, A. M.; Liu, F.; Quilter, J. H.; Glässl, M.; Axt, V. M.; Ramsay, A. J.; Skolnick, M. S.; Fox, A. M.

    2016-07-01

    The electron-phonon coupling in self-assembled InGaAs quantum dots is relatively weak at low light intensities, which means that the zero-phonon line in emission is strong compared to the phonon sideband. However, the coupling to acoustic phonons can be dynamically enhanced in the presence of an intense optical pulse tuned within the phonon sideband. Recent experiments have shown that this dynamic vibronic coupling can enable population inversion to be achieved when pumping with a blue-shifted laser and for rapid de-excitation of an inverted state with red detuning. In this paper we con?rm the incoherent nature of the phonon-assisted pumping process and explore the temperature dependence of the mechanism. We also show that a combination of blue- and red-shifted pulses can create and destroy an exciton within a timescale ~20 ps determined by the pulse duration and ultimately limited by the phonon thermalisation time.

  12. Inversion of Zeeman splitting of exciton states in InGaAs quantum wells

    NASA Astrophysics Data System (ADS)

    Grigoryev, P. S.; Yugov, O. A.; Eliseev, S. A.; Efimov, Yu. P.; Lovtcius, V. A.; Petrov, V. V.; Sapega, V. F.; Ignatiev, I. V.

    2016-05-01

    Zeeman splitting of quantum-confined states of excitons in InGaAs quantum wells (QWs) is experimentally found to depend strongly on quantization energy. Moreover, it changes sign when the quantization energy increases with a decrease in the QW width. In the 87-nm QW, the sign change is observed for the excited quantum-confined states, which are above the ground state only by a few meV. A two-step approach for the numerical solution of the two-particle Schrödinger equation, taking into account the Coulomb interaction and valence-band coupling, is used for a theoretical justification of the observed phenomenon. The calculated variation of the g -factor convincingly follows the dependencies obtained in the experiments.

  13. Electronic states and intraband terahertz optical transitions in InGaAs quantum rods

    NASA Astrophysics Data System (ADS)

    Prodanović, Nikola; Vukmirović, Nenad; Indjin, Dragan; Ikonić, Zoran; Harrison, Paul

    2012-04-01

    Strain-dependent eight-band k .p method is used to analyze the electronic structure and intraband optical transitions in self-assembled InGaAs quantum rods in the terahertz range. The calculation of absorption spectra for the growth- and in-plane-polarized radiation shows some similarities to those of quantum well and single quantum dot structures, augmented with contribution from transitions between the dot and quantum well states. The influence of rod height on the electronic structure and the intraband absorption spectra is also investigated. It is found that the energy of maximal terahertz absorption can be tailored by the rod height for both in-plane and in-growth polarized radiation.

  14. InGaAs vertical-cavity surface-emitting lasers

    SciTech Connect

    Geels, R.S.; Corzine, S.W.; Coldren, L.A. )

    1991-06-01

    In this paper the authors give theoretical and experimental results for vertical-cavity surface-emitting lasers (VCSEL's). The modeling is applied to the design of InGaAs VCSEL's A simple method is introduced to calculate the reflectivity of semiconductor stack mirrors with graded interfaces and compound metal/semiconductor stack mirrors. The theoretical predictions are compared to results from actual device measurements. A novel technique is introduced to determine material parameters: fabrication of in-plane lasers from VCSEL material. The procedure used to determine the optical model in such an in-plane laser is described. Using the insight gained from our modeling, we have increased our external efficiency to {gt}30% with a threshold current density of 1 kA/cm{sup 2}. Linewidth measurements on very high reflectivity VCSEL's have indicated widths as low as 85 MHz and linewidth-power products of 5 MHz {center dot} mW.

  15. Numerical modeling of extended short wave infrared InGaAs focal plane arrays

    NASA Astrophysics Data System (ADS)

    Glasmann, Andreu; Wen, Hanqing; Bellotti, Enrico

    2016-05-01

    Indium gallium arsenide (In1-xGaxAs) is an ideal material choice for short wave infrared (SWIR) imaging due to its low dark current and excellent collection efficiency. By increasing the indium composition from 53% to 83%, it is possible to decrease the energy gap from 0.74 eV to 0.47 eV and consequently increase the cutoff wavelength from 1.7 μm to 2.63 μm for extended short wavelength (ESWIR) sensing. In this work, we apply our well-established numerical modeling methodology to the ESWIR InGaAs system to determine the intrinsic performance of pixel detectors. Furthermore, we investigate the effects of different buffer/cap materials. To accomplish this, we have developed composition-dependent models for In1-xGaxAs, In1-xAlxAs, and InAs1-y Py. Using a Green's function formalism, we calculate the intrinsic recombination coefficients (Auger, radiative) to model the diffusion-limited behavior of the absorbing layer under ideal conditions. Our simulations indicate that, for a given total thickness of the buffer and absorbing layer, structures utilizing a linearly graded small-gap InGaAs buffer will produce two orders of magnitude more dark current than those with a wide gap, such as InAlAs or InAsP. Furthermore, when compared with experimental results for ESWIR photodiodes and arrays, we estimate that there is still a 1.5x magnitude of reduction in dark current before reaching diffusion-limited behavior.

  16. Development of high performance SWIR InGaAs focal plane array

    NASA Astrophysics Data System (ADS)

    Nagi, Richie; Bregman, Jeremy; Mizuno, Genki; Oduor, Patrick; Olah, Robert; Dutta, Achyut K.; Dhar, Nibir K.

    2015-05-01

    Banpil Photonics has developed a novel InGaAs based photodetector array for Short-Wave Infrared (SWIR) imaging, for the most demanding security, defense, and machine vision applications. These applications require low noise from both the detector and the readout integrated circuit arrays. In order to achieve high sensitivity, it is crucial to minimize the dark current generated by the photodiode array. This enables the sensor to function in extremely low light situations, which enables it to successfully exploit the benefits of the SWIR band. In addition to minimal dark current generation, it is essential to develop photodiode arrays with higher operating temperatures. This is critical for reducing the power consumption of the device, as less energy is spent in cooling down the focal plane array (in order to reduce the dark current). We at Banpil Photonics are designing, simulating, fabricating and testing SWIR InGaAs arrays, and have achieved low dark current density at room temperature. This paper describes Banpil's development of the photodetector array. We also highlight the fabrication technique used to reduce the amount of dark current generated by the photodiode array, in particular the surface leakage current. This technique involves the deposition of strongly negatively doped semiconductor material in the area between the pixels. This process reduces the number of dangling bonds present on the edges of each pixel, which prevents electrons from being swept across the surface of the pixels. This in turn drastically reduces the amount of surface leakage current at each pixel, which is a major contributor towards the total dark current. We present the optical and electrical characterization data, as well as the analysis that illustrates the dark current mechanisms. Also highlighted are the challenges and potential opportunities for further reduction of dark current, while maintaining other parameters of the photodiode array, such as size, weight, temperature

  17. Vacuum packaging of InGaAs focal plane array with four-stage thermoelectric cooler

    NASA Astrophysics Data System (ADS)

    Mo, De-feng; Liu, Da-fu; Yang, Li-yi; Xu, Qin-fei; Li, Xue

    2013-09-01

    The InGaAs focal plane array (FPA) detectors, covering the near-infrared 1~2.4 μm wavelength range, have been developed for application in space-based spectroscopy of the Earth atmosphere. This paper shows an all-metal vacuum package design for area array InGaAs detector of 1024×64 pixels, and its architecture will be given. Four-stage thermoelectric cooler (TEC) is used to cool down the FPA chip. To acquire high heat dissipation for TEC's Joule-heat, tungsten copper (CuW80) and kovar (4J29) is used as motherboard and cavity material respectively which joined by brazing. The heat loss including conduction, convection and radiation is analyzed. Finite element model is established to analyze the temperature uniformity of the chip substrate which is made of aluminum nitride (AlN). The performance of The TEC with and without heat load in vacuum condition is tested. The results show that the heat load has little influence to current-voltage relationship of TEC. The temperature difference (ΔT) increases as the input current increases. A linear relationship exists between heat load and ΔT of the TEC. Theoretical analysis and calculation show that the heat loss of radiation and conduction is about 187 mW and 82 mW respectively. Considering the Joule-heat of readout circuit and the heat loss of radiation and conduction, the FPA for a 220 K operation at room temperature can be achieved. As the thickness of AlN chip substrate is thicker than 1 millimeter, the temperature difference can be less than 0.3 K.

  18. Degradation processes in high power multi-mode InGaAs strained quantum well lasers

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Presser, Nathan; Foran, Brendan; Moss, Steven C.

    2009-02-01

    Recently, broad-area InGaAs-AlGaAs strained quantum well (QW) lasers have attracted much attention because of their unparalleled high optical output power characteristics that narrow stripe lasers or tapered lasers can not achieve. However, broad-area lasers suffer from poor beam quality and their high reliability operation has not been proven for communications applications. This paper concerns reliability and degradation aspects of broad-area lasers. Good facet passivation techniques along with optimized structural designs have led to successful demonstration of reliable 980nm single-mode lasers, and the dominant failure mode of both single-mode and broadarea lasers is catastrophic optical mirror damage (COMD), which limits maximum output powers and also determines operating output powers. Although broad-area lasers have shown characteristics unseen from singlemode lasers including filamentation, their effects on long-term reliability and degradation processes have not been fully investigated. Filamentation can lead to instantaneous increase in optical power density and thus temperature rise at localized areas through spatial-hole burning and thermal lensing which significantly reduces filament sizes under high power operation, enhancing the COMD process. We investigated degradation processes in commercial MOCVD-grown broad-area InGaAs-AlGaAs strained QW lasers at ~975nm with and without passivation layers by performing accelerated lifetests of these devices followed by failure mode analyses with various micro-analytical techniques. Since instantaneous fluctuations of filaments can lead to faster wear-out of passivation layer thus leading to facet degradation, both passivated and unpassivated broad-area lasers were studied that yielded catastrophic failures at the front facet and also in the bulk. Electron beam induced current technique was employed to study dark line defects (DLDs) generated in degraded lasers stressed under different test conditions and focused

  19. Testing of InGaAs, microbolometer and pyroelectric detectors in support of the EarthCARE mission

    NASA Astrophysics Data System (ADS)

    Hopkinson, Gordon; Gomez Rojas, Luis; Skipper, Mark; Meynart, Roland

    2008-10-01

    A test programme for infrared detectors in support of the EarthCARE mission is discussed. Commercially available linear InGaAs arrays from XenICs, Belgium (cut-off wavelengths 1.7, 2.2 and 2.5 μm), 384 x 288 amorphous silicon microbolometer arrays from ULIS, France and un-windowed single element lithium tantalate pyroelectric detectors from Infratec, Germany have been studied in detail to assess their suitability for EarthCARE and to provide performance data to aid in the design of the flight instruments. Tests included radiation resistance (cobalt60 and 60 MeV protons plus a heavy ion latch-up test for the InGaAs and microbolometer arrays), dark signal, noise, output stability, linearity, crosstalk and spectral response. In addition, the pyroelectric detectors were tested for low microphony.

  20. A simple device for measuring the spectral transmittance of lens used in InGaAs image intensifier apparatus

    NASA Astrophysics Data System (ADS)

    Bai, Xiaofeng; Guo, Hui; Yin, Lei; He, Yingping; Hou, Zhipeng; Miao, Zhuang; Yan, Lei

    2014-09-01

    In this article, in order to accurately measure the spectral transmittance of imaging lens used in InGaAs imaging apparatus, a simple device, which spectrum ranges from 400 nanometers to 2000 nanometers, based on double grating monochromator and self-collimating has been founded by using stable shortwave infrared radiant source, accurate double grating monochromator and telescope, stable silicon detector and cooled HgCdTe infrared detector. An imaging lens whose spectral transmittance has been known is measured on it. Comparing the test results to known data provided by manufacture, it is shown that the testing device founded in this article is competent to measure spectral transmittance of shortwave infrared imaging lens and which max relative deviation is no more than +/-2.5%. It is worthwhile for selecting InGaAs image intensifier assembly and evaluating the quality of shortwave infrared imaging lens.

  1. Study of strain boundary conditions and GaAs buffer sizes in InGaAs quantum dots

    NASA Technical Reports Server (NTRS)

    Oyafuso, F.; Klimeck, G.; Boykin, T. B.; Bowen, R. C.; Allmen, P. von

    2003-01-01

    NEMO 3-D has been developed for the simulation of electronic structure in self-assembled InGaAs quantum dots on GaAs substrates. Typical self-assembled quantum dots in that material system contain about 0.5 to 1 million atoms. Effects of strain by the surrounding GaAs buffer modify the electronic structure inside the quantum dot significantly and a large GaAs buffer must be included in the strain and electronic structure.

  2. Mechanical properties of Gd123 superconducting bulks at 77 K

    NASA Astrophysics Data System (ADS)

    Fujimoto, H.; Murakami, A.

    2012-05-01

    Mechanical properties of melt-grown GdBa2Cu3Ox (Gd123) large single-domain superconducting bulks with 10 wt% of Ag2O and 0.5 wt% of Pt have been evaluated at 77 K through flexural tests, on specimens cut from the samples, in order to estimate the mechanical properties of the Gd123 material without metal substrates, buffer layers or stabilization layers. The densified bulk was 46 mm in diameter and 25 mm in thickness, with low void density, and the standard bulk was around the same size, with voids. The results show that the mechanical properties of the densified Gd123 bulk with low void density are better than those of the standard Gd123 bulk with voids. We also compared the mechanical properties of as-grown bulks with those of annealed bulks. The relations between the microstructure and the flexural strength or the fracture toughness of the densified Gd123 bulk have been shown.

  3. Effects of forming gas anneal on ultrathin InGaAs nanowire metal-oxide-semiconductor field-effect transistors

    NASA Astrophysics Data System (ADS)

    Si, Mengwei; Gu, Jiangjiang J.; Wang, Xinwei; Shao, Jiayi; Li, Xuefei; Manfra, Michael J.; Gordon, Roy G.; Ye, Peide D.

    2013-03-01

    InGaAs gate-all-around metal-oxide-semiconductor field-effect transistors (MOSFETs) with 6 nm nanowire thickness have been experimentally demonstrated at sub-80 nm channel length. The effects of forming gas anneal (FGA) on the performance of these devices have been systematically studied. The 30 min 400 °C FGA (4% H2/96% N2) is found to improve the quality of the Al2O3/InGaAs interface, resulting in a subthreshold slope reduction over 20 mV/dec (from 117 mV/dec in average to 93 mV/dec). Moreover, the improvement of interface quality also has positive impact on the on-state device performance. A scaling metrics study has been carried out for FGA treated devices with channel lengths down to 20 nm, indicating excellent gate electrostatic control. With the FGA passivation and the ultra-thin nanowire structure, InGaAs MOSFETs are promising for future logic applications.

  4. Low dark current small pixel large format InGaAs 2D photodetector array development at Teledyne Judson Technologies

    NASA Astrophysics Data System (ADS)

    Yuan, Henry; Meixell, Mike; Zhang, Jiawen; Bey, Philip; Kimchi, Joe; Kilmer, Louis C.

    2012-06-01

    Teledyne Judson Technologies (TJT) has been developing technology for small pixel, large format, low dark current, and low capacitance NIR/SWIR InGaAs detector arrays, aiming to produce <10μm pixels and >2Kx2K format arrays that can be operated at or near room temperature. Furthermore, TJT is now developing technology for sub-10μm pixel arrays in response to requirements for a variety of low light level (LLL) imaging applications. In this paper, we will review test data that demonstrates lower dark current density for 10-20μm pixel arrays. We will present preliminary results on the successful fabrication of test arrays with pixels as small as 5μm. In addition, a lot of effort has been made to control and reduce the detector pixel capacitance which can become another source of detector noise. TJT is also developing 4" InGaAs wafer process and now offers four different types of InGaAs 2D arrays/FPAs that are tailored to different customer requirements for dark current, capacitance, spectral response, and bias range.

  5. Metal-organic vapor-phase epitaxy-grown ultra-low density InGaAs/GaAs quantum dots exhibiting cascaded single-photon emission at 1.3 μm

    SciTech Connect

    Paul, Matthias Kettler, Jan; Zeuner, Katharina; Clausen, Caterina; Jetter, Michael; Michler, Peter

    2015-03-23

    By metal-organic vapor-phase epitaxy, we have fabricated InGaAs quantum dots on GaAs substrate with an ultra-low lateral density (<10{sup 7} cm{sup −2}). The photoluminescence emission from the quantum dots is shifted to the telecom O-band at 1.31 μm by an InGaAs strain reducing layer. In time-resolved measurements, we find fast decay times for exciton (∼600 ps) and biexciton (∼300 ps). We demonstrate triggered single-photon emission (g{sup (2)}(0)=0.08) as well as cascaded emission from the biexciton decay. Our results suggest that these quantum dots can compete with their counterparts grown by state-of-the-art molecular beam epitaxy.

  6. Electrical and Optical Gain Lever Effects in InGaAs Double Quantum Well Diode Lasers

    SciTech Connect

    Pocha, M D; Goddard, L L; Bond, T C; Nikolic, R J; Vernon, S P; Kallman, J S; Behymer, E M

    2007-01-03

    In multisection laser diodes, the amplitude or frequency modulation (AM or FM) efficiency can be improved using the gain lever effect. To study gain lever, InGaAs double quantum well (DQW) edge emitting lasers have been fabricated with integrated passive waveguides and dual sections providing a range of split ratios from 1:1 to 9:1. Both the electrical and the optical gain lever have been examined. An electrical gain lever with greater than 7 dB enhancement of AM efficiency was achieved within the range of appropriate DC biasing currents, but this gain dropped rapidly outside this range. We observed a 4 dB gain in the optical AM efficiency under non-ideal biasing conditions. This value agreed with the measured gain for the electrical AM efficiency under similar conditions. We also examined the gain lever effect under large signal modulation for digital logic switching applications. To get a useful gain lever for optical gain quenched logic, a long control section is needed to preserve the gain lever strength and a long interaction length between the input optical signal and the lasing field of the diode must be provided. The gain lever parameter space has been fully characterized and validated against numerical simulations of a semi-3D hybrid beam propagation method (BPM) model for the coupled electron-photon rate equation. We find that the optical gain lever can be treated using the electrical injection model, once the absorption in the sample is known.

  7. Stray light characterization of an InGaAs anamorphic hyperspectral imager.

    PubMed

    Lin, Mike; Swanson, Rand; Moon, Thomas; Smith, Casey; Kehoe, Michael; Brown, Steven W; Lykke, Keith R

    2010-08-01

    Compact hyperspectral sensors potentially have a wide range of applications, including machine vision, quality control, and surveillance from small Unmanned Aerial Vehicles (UAVs). With the development of Indium Gallium Arsenide (InGaAs) focal plane arrays, much of the Short Wave Infra-Red (SWIR) spectral regime can be accessed with a small hyperspectral imaging system, thereby substantially expanding hyperspectral sensing capabilities. To fully realize this potential, system performance must be well-understood. Here, stray light characterization of a recently-developed push-broom hyperspectral sensor sensitive in the 1 microm -1.7 microm spectral regime is described. The sensor utilizes anamorphic fore-optics that partially decouple image formation along the spatial and spectral axes of the instrument. This design benefits from a reduction in complexity over standard high-performance spectrometer optical designs while maintaining excellent aberration control and spatial and spectral distortion characteristics. The stray light performance characteristics of the anamorphic imaging spectrometer were measured using the spectral irradiance and radiance responsivity calibrations using uniform sources (SIRCUS) facility at the National Institute of Standards and Technology (NIST). A description of the measurements and results are presented. Additionally, a stray-light matrix was assembled for the instrument to improve the instrument's spectral accuracy. Transmittance of a silicon wafer was measured to validate this approach. PMID:20721136

  8. Polarized and spatially resolved Raman scattering from composition-graded wurtzite InGaAs nanowires

    NASA Astrophysics Data System (ADS)

    Kim, H.; Rho, H.; Lee, E. H.; Song, J. D.

    2016-05-01

    We report Raman scattering from wurtzite single-crystalline InGaAs nanowires (NWs) to probe optical phonon behaviors associated with spatial grading in alloy composition along the NW length. Polarized Raman spectra revealed several optical phonons and their scattering symmetries: (i) InAs-like A 1(LO) and A 1(TO) phonons and (ii) GaAs-like A 1(LO), A 1(TO), and E 2(high) phonons. In addition, strong anisotropic behavior was observed in the Raman tensor elements of the A 1(TO) phonon mode. Interestingly, a spatial mapping of the GaAs-like A 1(TO) phonon along the NW length direction showed a systematic increase in energy from the NW top (~255 cm‑1) to the midpoint (~263 cm‑1), indicating an increase in the Ga mole fraction from about 0.5 to about 0.8. Further toward the NW bottom, the GaAs-like A 1(TO) phonon energy saturated to the peak value at about 264 cm‑1. In the upper half of the NW, the phonon linewidths broadened significantly due to the spatial grading in In/Ga composition along the NW length. When the composition grading was negligible in the bottom half of the NW, the spectral widths were considerably narrowed. The GaAs-like E 2(high) phonon showed similar variations in both energy and spectral width along the NW length.

  9. Reduction of sidewall interface recombination in GaAs and InGaAs active regions

    NASA Astrophysics Data System (ADS)

    Strand, Timothy Andrew

    In the continual effort to reduce the operating current in semiconductor lasers, the first step is always to reduce the size of the device. When we do so, however, we encounter a new set of challenges. As the device size decreases, the "walls close in" on the electrons and holes, that is, the sidewalls of the device become so close together that the electrons and holes can diffuse to them before recombining radiatively. The device sidewalls, are often littered with carrier traps, which act as nonradiative recombination sites for the electrons and holes. This wasted current, a small fraction of the total in larger devices, becomes the dominant current mechanism in small devices. In this work we present two techniques for limiting this sidewall interface recombination. The first uses semiconductor regrowth to remove the recombination sites that are normally formed at the air-exposed sidewalls. We use buried, in-plane lasers to demonstrate a reduction in the sidewall recombination rate by a factor of forty. In the second technique, we show that the sidewall interface recombination can also be reduced by preventing the carriers from diffusing to the sidewalls. We demonstrate two methods for reducing this lateral carrier diffusion; segmented GaAs quantum wells, and InGaAs quantum dots. In the former, we demonstrate a reduction in the low-temperature lateral carrier diffusion constant by a factor of forty-six (versus a comparable GaAs quantum well).

  10. Conduction mechanisms in ion-irradiated InGaAs layers

    SciTech Connect

    Joulaud, L.; Mangeney, J.; Chimot, N.; Crozat, P.; Fishman, G.; Bourgoin, J.C.

    2005-03-15

    The electrical and optical properties of H{sup +}- and Au{sup +}-irradiated InGaAs layers were studied using Hall-effect, van der Pauw, and relaxation-time measurements. Comparing the different results allows us to obtain information on the nature of the defects created by these two irradiations. Proton irradiation introduces donor-acceptor paired defects. Gold-ion irradiation creates neutral defect clusters and ionized point defects. The carrier mobilities in all of the irradiated materials are degraded, decreasing with increasing irradiation dose. A scattering model taking into account the paired defects is developed and the mobility evolution calculated from this model agrees with the experimental data of both annealed and unannealed samples. The photocurrent spectra reveal a metallic conduction in the band gap in the case of light-ion irradiation, while such type of conduction does not appear for heavy-ion irradiation. This metallic conduction is a consequence of band tailing induced by shallow defects and vanishes when the material is annealed at 400 deg. C. The proton irradiation-induced defects appear to be related to the EL-2-like defects.

  11. InGaAs PIN photodetectors integrated and vertically coupled with silicon-on-insulator waveguides

    NASA Astrophysics Data System (ADS)

    Wang, Zhiqi; Qiu, Chao; Sheng, Zhen; Wu, Aimin; Wang, Xi; Zou, Shichang; Gan, Fuwan

    2014-05-01

    Heterogeneous integration of III-V materials with silicon-on-insulator (SOI) waveguide circuitry by an adhesive die-to-wafer bonding process has been proposed as a solution to Si-based lasers and photodetectors. Here, we present the design and optimization of an InGaAs PIN photodetector vertically coupled with the underlying SOI waveguide, which could be readily fabricated using this bonding process. With the help of grating couplers, a thick bonding layer of 2.5 μm is applied, which inherently avoids the risk of low-bonding yield suffering in the evanescent coupling counterpart. An anti-reflection layer is also introduced between the bonding layer and the III-V layer stack to relieve the accuracy requirement for the bonding layer thickness. Besides, by optimizing the structure parameters, a high-absorption efficiency of 82% and a wide optical 1dB-bandwidth of 220nm are obtained. The analysis shows that the detection bandwidth of the present surface-illuminated photodetector is generally limited by transit-time in the i-InGaAs layer. The relationship of the detection bandwidth and the absorption efficiency versus the i-InGaAs layer thickness is presented for the ease of choosing proper structure parameters for specific applications. With the results presented here, the device can be readily fabricated.

  12. Impact of strain engineering on nanoscale strained InGaAs MOSFET devices.

    PubMed

    Lee, Chang-Chun; Chang, Shu-Tong; Sun, P-H; Huang, C-X

    2011-07-01

    The strain distributions in the In(0.53)Ga(0.47)As channel regions of the In(0.4)Ga(0.6)As source/drain (S/D) with various lengths and widths were studied via 3D process simulations. The resulting mobility improvement was analyzed. The tensile strain along the transport direction was found to dominate the mobility improvement. The strain along the vertical direction perpendicular to the gate oxide was found to affect the mobility the least, while the strain along the width direction was slightly degraded. The impact of the channel width and length on the performance improvement, such as on the mobility gain, was analyzed via TCAD simulations. The novelty of this paper stems from its study of the impact of the channel width and length on the performance of InGaAs NMOSFETs, such as on their mobility gain, and from its exploration of physical insights for scaling the future III-V MOS devices. PMID:22121581

  13. Induction detection of concealed bulk banknotes

    NASA Astrophysics Data System (ADS)

    Fuller, Christopher; Chen, Antao

    2011-10-01

    Bulk cash smuggling is a serious issue that has grown in volume in recent years. By building on the magnetic characteristics of paper currency, induction sensing is found to be capable of quickly detecting large masses of banknotes. The results show that this method is effective in detecting bulk cash through concealing materials such as plastics, cardboards, fabrics and aluminum foil. The significant difference in the observed phase between the received signals caused by conducting materials and ferrite compounds, found in banknotes, provides a good indication that this process can overcome the interference by metal objects in a real sensing application. This identification strategy has the potential to not only detect the presence of banknotes, but also the number, while still eliminating false positives caused by metal objects.

  14. Recent Progress in HTS Bulk Technology and Performance at NSC

    NASA Astrophysics Data System (ADS)

    Teshima, Hidekazu; Morita, Mitsuru

    This paper describes the current status of large single-grained RE-Ba-Cu-O (where RE: Y or rare earth elements) bulk superconductors with excellent superconducting properties in Nippon Steel Corporation. Intensive research on RE-Ba-Cu-O revealed that the optimal RE element is different for application requirements. While Gd-Ba-Cu-O bulk superconductors are greatly attractive for almost all bulk applications, Eu-Ba-Cu-O is suitable for compact NMR/MRI and Dy-Ba-Cu-O for current leads. In addition, single-domain bulk superconductors have been grown up to 150 mm in diameter by incorporating the RE compositional gradient method. Furthermore, progress of machining technology enables to obtain various complicated shapes of bulk superconductors.

  15. Hydrogels: DNA bulks up

    NASA Astrophysics Data System (ADS)

    Labean, Thom

    2006-10-01

    Since the 1940s DNA has been known as the genetic material connected to heredity, and from the early 1980s it has also been considered as a potential structural material for nanoscale construction. Now, a hydrogel made entirely of DNA brings this molecule into the realm of bulk materials.

  16. Growth of L-lysine monohydrochloride dihydrate bulk single crystal by Sankaranarayanan—Ramasamy (SR) method

    NASA Astrophysics Data System (ADS)

    Ramesh Babu, R.; Sethuraman, K.; Gopalakrishnan, R.; Ramasamy, P.

    2006-12-01

    Unidirectional bulk semi-organic nonlinear optical single crystal of L-lysine monohydrochloride dihydrate ( L-LMHCl) has been grown by Sankaranarayanan-Ramasamy (SR) method. The growth conditions have been optimized. The optical transparency of the grown crystal was measured.

  17. Electron mobility in ultra-thin InGaAs channels: Impact of surface orientation and different gate oxide materials

    NASA Astrophysics Data System (ADS)

    Krivec, Sabina; Poljak, Mirko; Suligoj, Tomislav

    2016-01-01

    Electron mobility is investigated in sub-20 nm-thick InGaAs channels, sandwiched between different gate oxides (SiO2, Al2O3, HfO2) and InP as substrate, using physics-based numerical modeling. Effects of body thickness downscaling to 2 nm, different gate oxides, and surface orientation [(1 0 0) and (1 1 1)] are examined by including all electron valleys and all relevant scattering mechanisms. We report that ultra-thin (1 1 1) Al2O3-InGaAs-InP devices offer greater electron mobility than (1 0 0) devices even in the extremely-thin channels. Furthermore, ultra-thin (1 0 0) InGaAs devices outperform SOI in terms of electron mobility for body thicknesses above ∼4 nm, while (1 1 1) InGaAs channels are superior to SOI for all body thickness values above ∼3 nm. The study of different gate oxides indicates that HfO2 is the optimum gate dielectric regardless of device orientation, offering a mobility improvement of up to 124% for (1 1 1) and 149% for (1 0 0) surface orientation, when compared to the initial Al2O3-InGaAs-InP structure. The (1 1 1) orientation offers improvement over (1 0 0) device irrespective of the body thickness and gate oxide material, with the highest difference reported for SiO2, followed by Al2O3 and HfO2.

  18. MBE-grown metamorphic lasers for applications at telecom wavelengths

    NASA Astrophysics Data System (ADS)

    Ledentsov, N. N.; Shchukin, V. A.; Kettler, T.; Posilovic, K.; Bimberg, D.; Karachinsky, L. Ya.; Gladyshev, A. Yu.; Maximov, M. V.; Novikov, I. I.; Shernyakov, Yu. M.; Zhukov, A. E.; Ustinov, V. M.; Kovsh, A. R.

    2007-04-01

    We have studied growth phenomena and structural and optical properties of metamorphic (MM) quantum dots (QDs) and QD lasers emitting in the 1.4-1.5 μm range. InAs/InGaAs QDs were grown on top of (In,Ga)As buffer layers deposited on GaAs (1 0 0) substrates. The wavelength of the QDs could be adjusted in the 1400-1600 nm spectral range by changing the composition of the (In,Ga)As matrix layer and by the amount of InAs deposited to form QDs. An additional wavelength shift can be achieved by strained-layer (In,Ga,Al)As overgrowth of the QDs. It is found that high-performance degradation-robust operation of the devices can be achieved through minimization of the defect density in the matrix material and within the QD sheets. A defect-reduction technique involving steps of strain-sensitive overgrowth and selective evaporation of the material in the defect-related areas was applied, leading to both elimination of dislocated clusters and blocking of propagating defects. MM QD lasers exhibited emission wavelength in the 1.4-1.5 μm range with a differential quantum efficiency of about ˜50% and pulsed power up to 7 W, limited by catastrophic optical mirror damage. The narrow-stripe lasers operate in a single transverse mode withstanding continuous wave current densities above 20 kA cm -2 without irreversible degradation. A maximum single mode continuous-wave output power of 220 mW limited by thermal roll-over is obtained. No beam filamentation was observed up to the highest pumping levels. Single-mode devices with as-cleaved facets are tested for 60 °C (800 h) and 70 °C (200 h) junction temperature. No noticeable degradation has been observed at 50 mW cw single mode output power, clearly manifesting for the first time degradation-free laser diodes on foreign substrates. The technology opens a way for integration of various III-V materials with silicon or germanium substrates for the next generation of microprocessors, optical interconnects and cascaded solar cells.

  19. Radiation performance of AlGaAs and InGaAs concentrator cells and expected performance of cascade structures

    NASA Technical Reports Server (NTRS)

    Curtis, H. B.; Swartz, C. K.; Hart, R. E., Jr.

    1987-01-01

    Aluminum gallium arsenide, GaAs, silicon and InGaAs cells have been irradiated with 1-MeV electrons and 37-MeV protons. These cells are candidates for individual cells in a cascade structure. Data are presented for both electron and proton irradiation studies for one sun and a concentration level of 100X AM0. Results of calculations on the radiation resistance of cascade cell structures based on the individual cell data are also presented. Both series-connected and separately connected structures are investigated.

  20. Long dephasing time and high temperature ballistic transport in an InGaAs open quantum dot

    NASA Astrophysics Data System (ADS)

    Hackens, B.; Faniel, S.; Delfosse, F.; Gustin, C.; Boutry, H.; Huynen, I.; Wallart, X.; Bollaert, S.; Cappy, A.; Bayot, V.

    2003-04-01

    We report on measurements of the magnetoconductance of an open circular InGaAs quantum dot between 1.3 and 204 K. We observe two types of magnetoconductance fluctuations: universal conductance fluctuations (UCFs), and “focusing” fluctuations related to ballistic trajectories between openings. The electron phase coherence time extracted from UCFs amplitude is larger than in GaAs/AlGaAs quantum dots and follows a similar temperature dependence (between T-1 and T-2). Below 150 K, the characteristic length associated with “focusing” fluctuations shows a slightly different temperature dependence from that of the conductivity.

  1. Detection of terahertz radiation by tightly concatenated InGaAs field-effect transistors integrated on a single chip

    SciTech Connect

    Popov, V. V.; Yermolaev, D. M.; Shapoval, S. Yu.; Maremyanin, K. V.; Gavrilenko, V. I.; Zemlyakov, V. E.; Bespalov, V. A.; Yegorkin, V. I.; Maleev, N. A.; Ustinov, V. M.

    2014-04-21

    A tightly concatenated chain of InGaAs field-effect transistors with an asymmetric T-gate in each transistor demonstrates strong terahertz photovoltaic response without using supplementary antenna elements. We obtain the responsivity above 1000 V/W and up to 2000 V/W for unbiased and drain-biased transistors in the chain, respectively, with the noise equivalent power below 10{sup −11} W/Hz{sup 0.5} in the unbiased mode of the detector operation.

  2. InGaAs triangular barrier photodiodes for high-responsivity detection of near-infrared light

    NASA Astrophysics Data System (ADS)

    Sugimura, Kazuya; Ohmori, Masato; Noda, Takeshi; Kojima, Tomoya; Kado, Sakunari; Vitushinskiy, Pavel; Iwata, Naotaka; Sakaki, Hiroyuki

    2016-06-01

    InGaAs triangular barrier (TB) structures of various barrier thicknesses have been formed on InP substrates. With them, we have fabricated TB photodiodes that yield a very high responsivity of 2.3 × 104 A/W at 100 K for the 1312 nm light of 320 fW power. By passivating the diode surface with polyimide, the dark current has been markedly reduced. Diodes with thicker barriers show higher sensitivity and responsivity, reflecting the enhancement of the barrier lowering effect by photogenerated holes.

  3. Electro-optical switching between polariton and cavity lasing in an InGaAs quantum well microcavity.

    PubMed

    Amthor, Matthias; Weißenseel, Sebastian; Fischer, Julian; Kamp, Martin; Schneider, Christian; Höfling, Sven

    2014-12-15

    We report on the condensation of microcavity exciton polaritons under optical excitation in a microcavity with four embedded InGaAs quantum wells. The polariton laser is characterized by a distinct non-linearity in the input-output-characteristics, which is accompanied by a drop of the emission linewidth indicating temporal coherence and a characteristic persisting emission blueshift with increased particle density. The temporal coherence of the device at threshold is underlined by a characteristic drop of the second order coherence function to a value close to 1. Furthermore an external electric field is used to switch between polariton regime, polariton condensate and photon lasing. PMID:25607064

  4. Bulk Email Forensics

    NASA Astrophysics Data System (ADS)

    Cohen, Fred

    Legal matters related to unsolicited commercial email often involve several hundred thousand messages. Manual examination and interpretation methods are unable to deal with such large volumes of evidence. Furthermore, as the actors gain experience, it is increasingly difficult to show evidence of spoliation and detect intentional evidence construction. This paper presents improved automated techniques for bulk email analysis and presentation to aid in evidence interpretation.

  5. Imaging Early Demineralization on Tooth Occlusal Surfaces with a High Definition InGaAs Camera

    PubMed Central

    Fried, William A.; Fried, Daniel; Chan, Kenneth H.; Darling, Cynthia L.

    2013-01-01

    In vivo and in vitro studies have shown that high contrast images of tooth demineralization can be acquired in the near-IR due to the high transparency of dental enamel. The purpose of this study is to compare the lesion contrast in reflectance at near-IR wavelengths coincident with high water absorption with those in the visible, the near-IR at 1300-nm and with fluorescence measurements for early lesions in occlusal surfaces. Twenty-four human molars were used in this in vitro study. Teeth were painted with an acid-resistant varnish, leaving a 4×4 mm window in the occlusal surface of each tooth exposed for demineralization. Artificial lesions were produced in the exposed windows after 1 & 2-day exposure to a demineralizing solution at pH 4.5. Lesions were imaged using NIR reflectance at 3 wavelengths, 1310, 1460 and 1600-nm using a high definition InGaAs camera. Visible light reflectance, and fluorescence with 405-nm excitation and detection at wavelengths greater than 500-nm were also used to acquire images for comparison. Crossed polarizers were used for reflectance measurements to reduce interference from specular reflectance. The contrast of both the 24 hr and 48 hr lesions were significantly higher (P<0.05) for NIR reflectance imaging at 1460-nm and 1600-nm than it was for NIR reflectance imaging at 1300-nm, visible reflectance imaging, and fluorescence. The results of this study suggest that NIR reflectance measurements at longer near-IR wavelengths coincident with higher water absorption are better suited for imaging early caries lesions. PMID:24357911

  6. Low phase noise high power handling InGaAs photodiodes for precise timing applications

    NASA Astrophysics Data System (ADS)

    Datta, Shubhashish; Joshi, Abhay; Becker, Don

    2009-05-01

    Time is the most precisely measured physical quantity. Such precision is achieved by optically probing hyperfine atomic transitions. These high Q-factor resonances demonstrate frequency instability of ~10-18 over 1 s observation time. Conversion of such a stable optical clock signal to an electrical clock through photodetection introduces additional phase noise, thereby resulting in a significant degradation in the frequency stability. This excess phase noise is primarily caused by the conversion of optical intensity noise into electrical phase noise by the phase non-linearity of the photodetector, characterized by its power-to-phase conversion factor. It is necessary to minimize this phase nonlinearity in order to develop the next generation of ultra-high precision electronic clocks. Reduction in excess phase noise must be achieved while ensuring a large output RF signal generated by the photodetector. The phase linearity in traditional system designs that employ a photoreceiver, namely a photodiode followed by a microwave amplifier, is limited by the phase non-linearity of the amplifier. Utilizing high-power handling photodiodes eliminates the need of microwave amplifiers. In this work, we present InGaAs p-i-n photodiodes that display a power-to-phase conversion factor <6 rad/W at a peak-to-peak RF output amplitude of 2 V. In comparison, the photodiode coupled to a transimpedance amplifier demonstrates >44 rad/W at a peak-to-peak RF output amplitude of 0.5 V. These results are supported by impulse response measurements at 1550 nm wavelength at 1 GHz repetition rate. These photodiodes are suitable of applications such as optical clock distribution networks, photonic analog-to-digital converters, and phased array radars.

  7. Imaging early demineralization on tooth occlusional surfaces with a high definition InGaAs camera

    NASA Astrophysics Data System (ADS)

    Fried, William A.; Fried, Daniel; Chan, Kenneth H.; Darling, Cynthia L.

    In vivo and in vitro studies have shown that high contrast images of tooth demineralization can be acquired in the near-IR due to the high transparency of dental enamel. The purpose of this study is to compare the lesion contrast in reflectance at near-IR wavelengths coincident with high water absorption with those in the visible, the near-IR at 1300-nm and with fluorescence measurements for early lesions in occlusal surfaces. Twenty-four human molars were used in this in vitro study. Teeth were painted with an acidresistant varnish, leaving a 4×4 mm window in the occlusal surface of each tooth exposed for demineralization. Artificial lesions were produced in the exposed windows after 1 and 2-day exposure to a demineralizing solution at pH 4.5. Lesions were imaged using NIR reflectance at 3 wavelengths, 1310, 1460 and 1600-nm using a high definition InGaAs camera. Visible light reflectance, and fluorescence with 405-nm excitation and detection at wavelengths greater than 500-nm were also used to acquire images for comparison. Crossed polarizers were used for reflectance measurements to reduce interference from specular reflectance. The contrast of both the 24 hr and 48 hr lesions were significantly higher (P<0.05) for NIR reflectance imaging at 1460-nm and 1600-nm than it was for NIR reflectance imaging at 1300-nm, visible reflectance imaging, and fluorescence. The results of this study suggest that NIR reflectance measurements at longer near-IR wavelengths coincident with higher water absorption are better suited for imaging early caries lesions.

  8. COUGAR: a liquid nitrogen cooled InGaAs camera for astronomy and electro-luminescence

    NASA Astrophysics Data System (ADS)

    Van Bogget, Urbain; Vervenne, Vincent; Vinella, Rosa Maria; van der Zanden, Koen; Merken, Patrick; Vermeiren, Jan

    2014-06-01

    A SWIR FPA was designed and manufactured with 640*512 pixels, 20 μm pitch and InGaAs detectors for electroluminescence characterization and astronomical applications in the [0.9 - 1.55 μm] range. The FPA is mounted in a liquid nitrogen dewar and is operated by a low noise frontend electronics. One of the biggest problem in designing sensors and cameras for electro-luminescence measurements is the autoillumination of the detectors by the readout circuit. Besides of proper shielding of the detectors, the ROIC shall be optimized for minimal electrical activity during the integration time of the very-weak signals coming from the circuit under test. For this reason a SFD (or Source Follower per Detector) architecture (like in the Hawaii sensor) was selected, resulting in a background limited performance of the detector. The pixel has a (somewhat arbitrary) full well capacity of 400 000 e- and a sensitivity of 2.17 μV/e-. The dark signal is app. 1 e-/pixel/sec and with the appropriate Fowler sampling the dark noise lowers below 5 e-rms. The power consumption of the circuit is limited 2 mW, allowing more than 24 hours of operation on less than 1 l of liquid nitrogen. The FPA is equipped with 4 outputs (optional readout on one single channel) and is capable of achieving 3 frames per second. Due to the non-destructive readout it is possible to determine in a dynamic way the optimal integration time for each observation. The Cougar camera is equipped with ultra-low noise power supply and bias lines; the electronics contain also a 24 bit AD converter to fully exploit the sensitivity of the FPA and the camera.

  9. Imaging surface plasmon polaritons using proximal self-assembled InGaAs quantum dots

    SciTech Connect

    Bracher, Gregor; Schraml, Konrad; Blauth, Mäx; Wierzbowski, Jakob; López, Nicolás Coca; Bichler, Max; Müller, Kai; Finley, Jonathan J.; Kaniber, Michael

    2014-07-21

    We present optical investigations of hybrid plasmonic nanosystems consisting of lithographically defined plasmonic Au-waveguides or beamsplitters on GaAs substrates coupled to proximal self-assembled InGaAs quantum dots. We designed a sample structure that enabled us to precisely tune the distance between quantum dots and the sample surface during nano-fabrication and demonstrated that non-radiative processes do not play a major role for separations down to ∼10 nm. A polarized laser beam focused on one end of the plasmonic nanostructure generates propagating surface plasmon polaritons that, in turn, create electron-hole pairs in the GaAs substrate during propagation. These free carriers are subsequently captured by the quantum dots ∼25 nm below the surface, giving rise to luminescence. The intensity of the spectrally integrated quantum dot luminescence is used to image the propagating plasmon modes. As the waveguide width reduces from 5 μm to 1 μm, we clearly observe different plasmonic modes at the remote waveguide end, enabling their direct imaging in real space. This imaging technique is applied to a plasmonic beamsplitter facilitating the determination of the splitting ratio between the two beamsplitter output ports as the interaction length L{sub i} is varied. A splitting ratio of 50:50 is observed for L{sub i}∼9±1 μm and 1 μm wide waveguides for excitation energies close to the GaAs band edge. Our experimental findings are in good agreement with mode profile and finite difference time domain simulations for both waveguides and beamsplitters.

  10. Fracture Toughness Properties of Gd123 Superconducting Bulks

    NASA Astrophysics Data System (ADS)

    Fujimoto, H.; Murakami, A.

    Fracture toughness properties of melt growth GdBa2Cu3Ox (Gd123) large single domain superconducting bulks with Ag2O of 10 wt% and Pt of 0.5 wt%; 45 mm in diameter and 25 mm in thickness with low void density were evaluated at 77 K through flexural tests of specimens cut from the bulks, and compared to those of a conventional Gd123 with voids. The densified Gd123 bulks were prepared with a seeding and temperature gradient method; first melt processed in oxygen, then crystal growth in air; two-step regulated atmosphere heat treatment. The plane strain fracture toughness, KIC was obtained by the three point flexure test of the specimens with through precrack, referring to the single edge pre-cracked beam (SEPB) method, according to the JIS-R-1607, Testing Methods for Fracture Toughness of High Performance Ceramics. The results show that the fracture toughness of the densified Gd123 bulk with low void density was higher than that of the standard Gd123 bulk with voids, as well as the flexural strength previously reported. We also compared the fracture toughness of as-grown bulks with that of annealed bulks. The relation between the microstructure and the fracture toughness of the Gd123 bulk was clearly shown.

  11. Bulk-barrier transistor

    NASA Astrophysics Data System (ADS)

    Mader, H.; Mueller, R.; Beinvogl, W.

    1983-10-01

    Experimental and theoretical results are presented on a bulk-barrier transistor (BBT). In this device the charge-carrier transportation is determined by an energy barrier, which is located inside a semiconductor. The barrier is the result of a space-charge region in a three-layered n-p-n or p-n-p structure with a very thin middle layer. The height of the energy barrier, which is adjustable by technological parameters, can be controlled by an external voltage.

  12. Surfactant-assisted growth and properties of rare-earth arsenide InGaAs nanocomposites for terahertz generation

    NASA Astrophysics Data System (ADS)

    Salas, R.; Guchhait, S.; McNicholas, K. M.; Sifferman, S. D.; Dasika, V. D.; Jung, D.; Krivoy, E. M.; Lee, M. L.; Bank, S. R.

    2016-05-01

    We explore the effects of surfactant-mediated epitaxy on the structural, electrical, and optical properties of fast metal-semiconductor superlattice photoconductors. Specifically, application of a bismuth flux during growth was found to significantly improve the properties of superlattices of LuAs nanoparticles embedded in In0.53Ga0.47As. These improvements are attributed to the enhanced structural quality of the overgrown InGaAs over the LuAs nanoparticles. The use of bismuth enabled a 30% increase in the number of monolayers of LuAs that could be deposited before the InGaAs overgrowth degraded. Dark resistivity increased by up to ˜15× while carrier mobility remained over 2300 cm2/V-s and carrier lifetimes were reduced by >2× at comparable levels of LuAs deposition. These findings demonstrate that surfactant-mediated epitaxy is a promising approach to enhance the properties of ultrafast photoconductors for terahert generation.

  13. Analysis and design of a low-noise ROIC for hybrid InGaAs infrared FPA

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Huang, SongLei; Huang, ZhangCheng; Fang, Jiaxiong

    2011-08-01

    The noises of CMOS readout integrated circuit (ROIC) for hybrid focal plane array (FPA) may occupy a great part of total noise in conditions that a low resistance or large capacitor detector interfacing with CTIA input stage. A novel low noise low power preamplifier with shared current-mirrors bias is designed. It has a gain of more than 90dB, which makes enough inject efficiency and low detector bias offset. Besides, it has strong detector bias control, because the shared current-mirror copies the DC current of the amplifier and generates the bias control voltage. A pixel level Correlated Double Sample circuits is designed in order to suppress the reset KTC noise and 1/f noise from preamplifier. An experimental chip of 30μm pitch 32×32 array was fabricated in standard 0.5μm CMOS mixed signal process. A few experimental structures are designed to study the allocating of layout area for low noise designing. The ROIC is bonded to an existing back-illuminated 30μm pitch InGaAs photodiode array with indium bump fabrication. The test of both the ROIC chips and InGaAs focal plane array is shown in this paper, and the contrast of different structure is shown and analyzed.

  14. An uncooled 1280 x 1024 InGaAs focal plane array for small platform, shortwave infrared imaging

    NASA Astrophysics Data System (ADS)

    Battaglia, J.; Blessinger, M.; Enriquez, M.; Ettenberg, M.; Evans, M.; Flynn, K.; Lin, M.; Passe, J.; Stern, M.; Sudol, T.

    2009-05-01

    The increasing demand for short wave infrared (SWIR) imaging technology for soldier-based and unmanned platforms requires camera systems where size, weight and power consumption are minimized without loss of performance. Goodrich, Sensors Unlimited Inc. reports on the development of a novel focal plane (FPA) array for DARPA's MISI (Micro-Sensors for Imaging) Program. This large format (1280 x 1024) array is optimized for day/night imaging in the wavelength region from 0.4 μm to 1.7 μm and consists of an InGaAs detector bump bonded to a capacitance transimpedance amplifier (CTIA)-based readout integrated circuit (ROIC) on a compact 15 μm pixel pitch. Two selectable integration capacitors provide for high dynamic range with low (< 50 electrons) noise, and expanded onchip ROIC functionality includes analog-to-digital conversion and temperature sensing. The combination of high quality, low dark current InGaAs with temperature-parameterized non-uniformity correction allows operation at ambient temperatures while eliminating the need for thermoelectric cooling. The resulting lightweight, low power implementation is suitable for man-portable and UAV-mounted applications.

  15. Beyond hydrostatic strain in empirical pseudopotentials for the electronic structure of InGaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Bulutay, Ceyhun; Cakan, Asli

    2015-03-01

    Self-assembled quantum dots (SAQDs) are among the prime candidates for realizing semiconductor qubits. Even though much progress has been achieved toward understanding their electronic structure, more efforts are needed to reach the desired quantitative level for a precise control of the carrier and nuclear spin degrees of freedom. In this respect, the empirical pseudopotential method has been highly successful for structures involving more than hundred thousand atoms. However, due to lack of self-consistency, their use in strained environments, as in SAQDS, requires vital improvement. The main contribution of this work is to develop empirical pseudopotentials valid for inhomogeneous strain environments caused by cation alloying in InGaAs SAQDs. In our presentation, we first validate our approach with the ab initio density functional theory results based on Projector Augmented-Wave technique. This is followed by a comparison of the electronic structure results with and without strain-dependent pseudopotentials for InGaAs SAQDs having an alloy composition of 20-30% indium, which is typically the case in the current samples. Supported by TUBITAK with the Project No. 112T178.

  16. Analysis of high frame rate readout circuit for near-infrared InGaAs focal plane array

    NASA Astrophysics Data System (ADS)

    Huang, Zhangcheng; Chen, Yu; Huang, Songlei; Fang, Jiaxiong

    2013-09-01

    High frame rate imaging for applications such as meteorological forecast, motion target tracking require high-speed Read-Out Integrated Circuit (ROIC). In order to achieve 10 KHz of frame rate, this paper analyzes the bandwidth of Capacitive-feedback Trans-Impedance Amplifier (CTIA) in ROIC which is the dominant bandwidth-limiting node when interfaced with large InGaAs detector pixel capacitance of about 10pF. A small-signal model is presented to study the relationship between integration capacitance, detector capacitance, transconductance and CTIA bandwidth. Calculation and simulation results show explicitly how the series resistance at the interface restricts the frame rate of Focal Plane Arrays (FPA). In order to achieve low-noise performance at a high frame rate, this paper describes an optimal solution in ROIC design. A prototype ROIC chip (DL7) has been fabricated with 0.5-μm mixed signal CMOS process and interfaced with InGaAs detector arrays. Test results show that frame rate is above 10 KHz and ROIC noise is around 270 e-, near identical to the design value.

  17. Analysis of crosstalk in front-illuminated InGaAs PIN hetero-junction photovoltaic infrared detector arrays

    NASA Astrophysics Data System (ADS)

    Li, Yongfu; Tang, Hengjing; Zhang, Kefeng; Li, Tao; Ning, Jinhua; Li, Xue; Gong, Haimei

    2009-07-01

    Here presented an experimental study on crosstalk in front illuminated planar and mesa-type InP/ InGaAs/ InP PIN hetero-junction photovoltaic infrared detector arrays. A scanning laser beam with an optical wavelength of 1310 nm coupled in a single-mode optical fiber placed within a few microns of the detector array surface was used to measure the crosstalk between the detector pixels. The crosstalk in the detector array varying with the distance between the incident laser spot and the measured pixel was shown. It is suggested that for the deep mesa-type arrays the dominating source of crosstalk is the light reflected from the detector substrate. And the dominating source of crosstalk that occurs in the planar type and shallow mesa type photovoltaic arrays is associated with photo-induced carries generated in the InGaAs absorption layer that diffuse laterally between neighbor pixels. These results gave out the possibility to optimize the detectors structures in order to reduce crosstalk.

  18. Effect of multilayer barriers on the optical properties of GaInNAs single quantum-well structures grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Sun, H. D.; Clark, A. H.; Calvez, S.; Dawson, M. D.; Kim, K. S.; Kim, T.; Park, Y. J.

    2005-07-01

    We report on the effects of combined strain-compensating and strain-mediating layers of various widths on the optical properties of 1.3 μm GaInNAs/GaAs single quantum well structures grown by metalorganic vapor phase epitaxy (MOVPE). While the emission wavelength of GaInNAs/GaAs quantum wells can be redshifted by the adoption of strain-compensated GaNAs layers, the material quality is degraded by the increased stress at the well/barrier interface. This detrimental effect can be cured by inserting a strain-mediating InGaAs layer between them. Contrary to what is expected, however, the emission wavelength is blueshifted by the insertion of the InGaAs layer, which is attributed to the reduced N incorporation due to the improved interface quality. Our results indicate that the optical properties of MOVPE-grown GaInNAs/GaAs quantum wells can be optimized in quantum efficiency and emission wavelength by combination of strain-compensating and strain-mediating layers with suitable characteristics.

  19. Graphic Grown Up

    ERIC Educational Resources Information Center

    Kim, Ann

    2009-01-01

    It's no secret that children and YAs are clued in to graphic novels (GNs) and that comics-loving adults are positively giddy that this format is getting the recognition it deserves. Still, there is a whole swath of library card-carrying grown-up readers out there with no idea where to start. Splashy movies such as "300" and "Spider-Man" and their…

  20. Analysis of Carrier Recombination Processes in 0.6 eV InGaAs Epitaxial Materials for Thermophotovoltaic Devices

    SciTech Connect

    D Donetsky; F Newman; M Dashiell

    2006-10-30

    Minority carrier lifetime was measured by time-resolved photoluminescence (TRPL) method in sets of p-type and n-type InGaAs double heterostructures (DH) moderately doped with Zn and Te, respectively. Contributions of the radiative and non-radiative recombination terms were separated by fitting experimental data to temperature dependences of the radiative term. The latter was modeled with measured fundamental absorption spectrum and the temperature dependence of the photon recycling effect was taken into account. Different temperature dependences of radiative terms for electron and hole materials were obtained. It was concluded that in 0.6 eV Te-doped InGaAs structures the radiative recombination controls the hole lifetime at liquid nitrogen temperatures, while Auger recombination dominates at room and above room temperatures. In similar 0.6 eV InGaAs with Zn-doped active regions Shockley-Read-Hall (SRH) recombination was found dominant in a wide temperature range from liquid nitrogen to above-room temperatures. Rapid decrease of electron lifetime with decrease of excess carrier concentration was observed and attributed to recombination through partially-ionized deep donor centers. The obtained data allows for more adequate modeling of the performance and design optimization of narrow-gap photonic devices based on InGaAs Indium-rich compounds.

  1. Design of 800×2 low-noise readout circuit for near-infrared InGaAs focal plane array

    NASA Astrophysics Data System (ADS)

    Huang, Zhangcheng; Huang, Songlei; Fang, Jiaxiong

    2012-12-01

    InGaAs near-infrared (NIR) focal plane arrays (FPA) have important applications in space remote sensing. A design of 800×2 low-noise readout integrated circuit (T800 ROIC) with a pitch of 25 μm is presented for a dual-band monolithic InGaAs FPA. Mathematical analysis and transient noise simulations have been presented for predicting and lowering the noise in T800 ROIC. Thermal noise from input-stage amplifier which plays a dominant role in ROIC is reduced by increasing load capacitor under tradeoff and a low input offset voltage in the range of +/-5 mV is obtained by optimizing transistors in the input-stage amplifier. T800 ROIC has been fabricated with 0.5-μm 5V mixed signal CMOS process and interfaced with InGaAs detector arrays. Test results show that ROIC noise is around 90 μV and input offset voltage shows a good correspondence with simulation results. 800×2 InGaAs FPA has a peak detectivity (D*) of about 1.1×1012 cmHz1/2/ W, with dynamic range of above 80dB.

  2. Ultra-low dark current InGaAs technology for focal plane arrays for low-light level visible-shortwave infrared imaging

    NASA Astrophysics Data System (ADS)

    Onat, Bora M.; Huang, Wei; Masaun, Navneet; Lange, Michael; Ettenberg, Martin H.; Dries, Christopher

    2007-04-01

    Under the DARPA Photon Counting Arrays (PCAR) program we have investigated technologies to reduce the overall noise level in InGaAs based imagers for identifying a man at 100m under low-light level imaging conditions. We report the results of our experiments comprising of 15 InGaAs wafers that were utilized to investigate lowering dark current in photodiode arrays. As a result of these experiments, we have achieved an ultra low dark current of 2nA/cm2 through technological advances in InGaAs detector design, epitaxial growth, and processing at a temperature of +12.3 degrees C. The InGaAs photodiode array was hybridized to a low noise readout integrated circuit, also developed under this program. The focal plane array (FPA) achieves very high sensitivity in the shortwave infrared bands in addition to the visible response added via substrate removal process post hybridization. Based on our current room-temperature stabilized SWIR camera platform, these imagers enable a full day-night imaging capability and are responsive to currently fielded covert laser designators, illuminators, and rangefinders. In addition, improved haze penetration in the SWIR compared to the visible provides enhanced clarity in the imagery of a scene. In this paper we show the results of our dark current studies as well as FPA characterization of the camera built under this program.

  3. Bulk material handling system

    DOEpatents

    Kleysteuber, William K.; Mayercheck, William D.

    1979-01-01

    This disclosure relates to a bulk material handling system particularly adapted for underground mining and includes a monorail supported overhead and carrying a plurality of conveyors each having input and output end portions with the output end portion of a first of the conveyors positioned above an input end portion of a second of the conveyors, a device for imparting motion to the conveyors to move the material from the input end portions toward the output end portions thereof, a device for supporting at least one of the input and output end portions of the first and second conveyors from the monorail, and the supporting device including a plurality of trolleys rollingly supported by the monorail whereby the conveyors can be readily moved therealong.

  4. Bulk amorphous materials

    SciTech Connect

    Schwarz, R.B.; Archuleta, J.I.; Sickafus, K.E.

    1998-12-01

    This is the final report for a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this work was to develop the competency for the synthesis of novel bulk amorphous alloys. The authors researched their synthesis methods and alloy properties, including thermal stability, mechanical, and transport properties. The project also addressed the development of vanadium-spinel alloys for structural applications in hostile environments, the measurement of elastic constants and thermal expansion in single-crystal TiAl from 300 to 750 K, the measurement of elastic constants in gallium nitride, and a study of the shock-induced martensitic transformations in NiTi alloys.

  5. Bulk muscles, loose cables.

    PubMed

    Liyanage, Chamari R D G; Kodali, Venkata

    2014-01-01

    The accessibility and usage of body building supplements is on the rise with stronger internet marketing strategies by the industry. The dangers posed by the ingredients in them are underestimated. A healthy young man came to the emergency room with palpitations and feeling unwell. Initial history and clinical examination were non-contributory to find the cause. ECG showed atrial fibrillation. A detailed history for any over the counter or herbal medicine use confirmed that he was taking supplements to bulk muscle. One of the components in these supplements is yohimbine; the onset of symptoms coincided with the ingestion of this product and the patient is symptom free after stopping it. This report highlights the dangers to the public of consuming over the counter products with unknown ingredients and the consequential detrimental impact on health. PMID:25326558

  6. Creating bulk nanocrystalline metal.

    SciTech Connect

    Fredenburg, D. Anthony; Saldana, Christopher J.; Gill, David D.; Hall, Aaron Christopher; Roemer, Timothy John; Vogler, Tracy John; Yang, Pin

    2008-10-01

    Nanocrystalline and nanostructured materials offer unique microstructure-dependent properties that are superior to coarse-grained materials. These materials have been shown to have very high hardness, strength, and wear resistance. However, most current methods of producing nanostructured materials in weapons-relevant materials create powdered metal that must be consolidated into bulk form to be useful. Conventional consolidation methods are not appropriate due to the need to maintain the nanocrystalline structure. This research investigated new ways of creating nanocrystalline material, new methods of consolidating nanocrystalline material, and an analysis of these different methods of creation and consolidation to evaluate their applicability to mesoscale weapons applications where part features are often under 100 {micro}m wide and the material's microstructure must be very small to give homogeneous properties across the feature.

  7. Explosive bulk charge

    DOEpatents

    Miller, Jacob Lee

    2015-04-21

    An explosive bulk charge, including: a first contact surface configured to be selectively disposed substantially adjacent to a structure or material; a second end surface configured to selectively receive a detonator; and a curvilinear side surface joining the first contact surface and the second end surface. The first contact surface, the second end surface, and the curvilinear side surface form a bi-truncated hemispherical structure. The first contact surface, the second end surface, and the curvilinear side surface are formed from an explosive material. Optionally, the first contact surface and the second end surface each have a substantially circular shape. Optionally, the first contact surface and the second end surface consist of planar structures that are aligned substantially parallel or slightly tilted with respect to one another. The curvilinear side surface has one of a smooth curved geometry, an elliptical geometry, and a parabolic geometry.

  8. Low-noise InGaAs infrared 1.0- to 2.4-μm focal plane arrays for SCIAMACHY

    NASA Astrophysics Data System (ADS)

    van der A, Ronald J.; Hoogeveen, Ruud W. M.; Spruijt, Hugo J.; Goede, Albert P. H.

    1997-01-01

    SCIAMACHY has been selected for the ESA environmental satellite ENVISAT with the objective to carry out atmospheric research in the UV, VIS, and IR spectral range. The most innovative parts of the instrument are the low- noise InGaAs semiconductor focal plane arrays covering the 1.0-2.4 micrometers wavelength range. For the first time InGaAs focal plane arrays with an extended wavelength range have become space qualified. In this paper theory and measurement of the dark current and noise behavior of these detectors is presented. Each InGaAs focal plane array consists of a 1024 pixel linear photo-detecting sliver and two 512 pixel multiplexing read-out chips. Each multiplexer contains 512 individual charge transimpedance amplifier and correlated double sampling circuits. A cylindrical lens, integrated in the detector housing, focuses the light on detector in the cross-dispersion direction. The InGaAs composition of the detectors is tuned to match the required wavelength range. Measurements have been performed of the dark current and noise as function of temperature and bias voltage in order to relate their performance to theory presented in this paper. InGaAs detectors sensitive to 2400 nm wavelength achieve dark current levels as low as 20-100 fA per detector pixel area of 1.25 (DOT) 10-4 cm2 at an operating temperature of 150 K and a bias voltage of 2 mV. Lower temperatures further reduce the dark current but also decrease the quantum efficiency at long wavelengths, yielding no net gain in performance. The development programme of these SCIAMACHY detectors has been carried out by Epitaxx Inc., for and in cooperation with the Space Research Organization Netherlands.

  9. InP/InGaAs/InP DHBT structures with graded composition base grown by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Teng, Teng; Ai, Likun; Xu, Anhuai; Sun, Hao; Zhu, Fuying; Qi, Ming

    2011-05-01

    A new InP/InGaAs/InP DHBT structure with graded composition base was optimized and grown successfully in this work. The gallium (Ga) composition increased gradually from 47% on the collector side to 55% on the emitter side. The InP/InGaAs/InP DHBT structures were grown by gas source molecular beam epitaxy (GSMBE). Characteristics of InP, InGaAs and InGaAsP materials were investigated. High quality InP/InGaAs/InP DHBT structural materials were obtained. The InP/InGaAs/InP DHBT device with emitter area of 100×100 μm2 was fabricated. The offset voltage of 0.2 V, BVCEO>1.2 V, current gain of ß=550 at VCE of 1.0 V were achieved. The reasons for the low breakdown voltage were analyzed.

  10. Light-trapping for room temperature Bose-Einstein condensation in InGaAs quantum wells.

    PubMed

    Vasudev, Pranai; Jiang, Jian-Hua; John, Sajeev

    2016-06-27

    We demonstrate the possibility of room-temperature, thermal equilibrium Bose-Einstein condensation (BEC) of exciton-polaritons in a multiple quantum well (QW) system composed of InGaAs quantum wells surrounded by InP barriers, allowing for the emission of light near telecommunication wavelengths. The QWs are embedded in a cavity consisting of double slanted pore (SP2) photonic crystals composed of InP. We consider exciton-polaritons that result from the strong coupling between the multiple quantum well excitons and photons in the lowest planar guided mode within the photonic band gap (PBG) of the photonic crystal cavity. The collective coupling of three QWs results in a vacuum Rabi splitting of 3% of the bare exciton recombination energy. Due to the full three-dimensional PBG exhibited by the SP2 photonic crystal (16% gap to mid-gap frequency ratio), the radiative decay of polaritons is eliminated in all directions. Due to the short exciton-phonon scattering time in InGaAs quantum wells of 0.5 ps and the exciton non-radiative decay time of 200 ps at room temperature, polaritons can achieve thermal equilibrium with the host lattice to form an equilibrium BEC. Using a SP2 photonic crystal with a lattice constant of a = 516 nm, a unit cell height of 2a=730nm and a pore radius of 0.305a = 157 nm, light in the lowest planar guided mode is strongly localized in the central slab layer. The central slab layer consists of 3 nm InGaAs quantum wells with 7 nm InP barriers, in which excitons have a recombination energy of 0.944 eV, a binding energy of 7 meV and a Bohr radius of aB = 10 nm. We take the exciton recombination energy to be detuned 35 meV above the lowest guided photonic mode so that an exciton-polariton has a photonic fraction of approximately 97% per QW. This increases the energy range of small-effective-mass photonlike states and increases the critical temperature for the onset of a Bose-Einstein condensate. With three quantum wells in the central slab layer

  11. Bulk Data Mover

    SciTech Connect

    2011-01-03

    Bulk Data Mover (BDM) is a high-level data transfer management tool. BDM handles the issue of large variance in file sizes and a big portion of small files by managing the file transfers with optimized transfer queue and concurrency management algorithms. For example, climate simulation data sets are characterized by large volume of files with extreme variance in file sizes. The BDN achieves high performance using a variety of techniques, including multi-thraded concurrent transfer connections, data channel caching, load balancing over multiple transfer servers, and storage i/o pre-fetching. Logging information from the BDM is collected and analyzed to study the effectiveness of the transfer management algorithms. The BDM can accept a request composed of multiple files or an entire directory. The request also contains the target site and directory where the replicated files will reside. If a directory is provided at the source, then the BDM will replicate the structure of the source directory at the target site. The BDM is capable of transferring multiple files concurrently as well as using parallel TCP streams. The optimal level of concurrency or parallel streams depends on the bandwidth capacity of the storage systems at both ends of the transfer as well as achievable bandwidth of the wide-area network. Hardware req.-PC, MAC, Multi-platform & Workstation; Software req.: Compile/version-Java 1.50_x or ablove; Type of files: source code, executable modules, installation instructions other, user guide; URL: http://sdm.lbl.gov/bdm/

  12. Poisson Ratio of Epitaxial Germanium Films Grown on Silicon

    NASA Astrophysics Data System (ADS)

    Bharathan, Jayesh; Narayan, Jagdish; Rozgonyi, George; Bulman, Gary E.

    2013-01-01

    An accurate knowledge of elastic constants of thin films is important in understanding the effect of strain on material properties. We have used residual thermal strain to measure the Poisson ratio of Ge films grown on Si ⟨001⟩ substrates, using the sin2 ψ method and high-resolution x-ray diffraction. The Poisson ratio of the Ge films was measured to be 0.25, compared with the bulk value of 0.27. Our study indicates that use of Poisson ratio instead of bulk compliance values yields a more accurate description of the state of in-plane strain present in the film.

  13. New design of InGaAs guided-mode resonance photodiode for SWIR low dark current imaging

    NASA Astrophysics Data System (ADS)

    Verdun, Michaël.; Portier, Benjamin; Jaworowicz, Katarzyna; Jaeck, Julien; Dupuis, Christophe; Haidar, Riad; Pardo, Fabrice; Pelouard, Jean-Luc

    2016-04-01

    We investigate a full-dielectric guided mode resonant photodiode. It has been designed to enhance the absorption by excitation of several resonances in the SWIR domain. The device consists of an InP/InGaAs/InP P-i-N heterojunction containing an active layer as thin as 90 nm on top of a subwavelength lamellar grating and a gold mirror. We successfully compared the electro-optical characterizations of individual pixels with electro-magnetic simulations. In particular, we observe near perfect collection of the photo-carriers and external quantum efficiency (EQE) of up to 71% around 1.55 μm. Moreover, compared with InGaAs resonator state-of-the-art detector, we show a broader spectral response in the 1.2-1.7 μm range, thus paving the way for SWIR low dark current imaging.

  14. Characteristics of the dynamics of breakdown filaments in Al2O3/InGaAs stacks

    NASA Astrophysics Data System (ADS)

    Palumbo, F.; Shekhter, P.; Cohen Weinfeld, K.; Eizenberg, M.

    2015-09-01

    In this paper, the Al2O3/InGaAs interface was studied by X-ray photoelectron spectroscopy (XPS) after a breakdown (BD) event at positive bias applied to the gate contact. The dynamics of the BD event were studied by comparable XPS measurements with different current compliance levels during the BD event. The overall results show that indium atoms from the substrate move towards the oxide by an electro-migration process and oxidize upon arrival following a power law dependence on the current compliance of the BD event. Such a result reveals the physical feature of the breakdown characteristics of III-V based metal-oxide-semiconductor devices.

  15. InGaAs Schottky barrier diode array detector for a real-time compact terahertz line scanner.

    PubMed

    Han, Sang-Pil; Ko, Hyunsung; Park, Jeong-Woo; Kim, Namje; Yoon, Young-Jong; Shin, Jun-Hwan; Kim, Dae Yong; Lee, Dong Hun; Park, Kyung Hyun

    2013-11-01

    We present a terahertz (THz) broadband antenna-integrated 1 × 20 InGaAs Schottky barrier diode (SBD) array detector with an average responsivity of 98.5 V/W at a frequency of 250 GHz, which is measured without attaching external amplifiers and Si lenses, and an average noise equivalent power (NEP) of 106.6 pW/√Hz. The 3-dB bandwidth of the SBD detector is also investigated at approximately 180 GHz. For implementing an array-type SBD detector by a simple fabrication process to achieve a high yield, a structure comprising an SiN(x) layer instead of an air bridge between the anode and the cathode is designed. THz line beam imaging using a Gunn diode emitter with a center frequency of 250 GHz and a 1 × 20 SBD array detector is successfully demonstrated. PMID:24216813

  16. Analysis of cross talk in high density mesa linear InGaAs detector arrays using tiny light dot

    NASA Astrophysics Data System (ADS)

    Zhu, Yaoming; Li, Xue; Wei, Jun; Li, Jianwei; Tang, Hengjing; Gong, Hai-mei

    2012-10-01

    With the development of material growth and device technologies, the pixel density becomes much higher. The pixel size and the spacing between pixels have been becoming smaller and smaller, causing the cross talk of the neighboring pixels acuter. Linear InGaAs detector arrays with 25 μm pitch and 2 μm spacing were fabricated, and the modulation transfer function of detector arrays with infrared lens was measured using a system of collimator tube. A tiny light dot produced by the collimator tube was used to analyze and calculated the cross talk of the detector with conserved absorber around the photosensitive mesa, and the cross talk between two neighboring pixels was approximately estimated. With the conserved absorber structure, the electronic cross talk is dominant in the cross talks between neighboring pixels.

  17. Experimental demonstration of hot-carrier photo-current in an InGaAs quantum well solar cell

    SciTech Connect

    Hirst, L. C.; Walters, R. J.; Führer, M. F.; Ekins-Daukes, N. J.

    2014-06-09

    An unambiguous observation of hot-carrier photocurrent from an InGaAs single quantum well solar cell is reported. Simultaneous photo-current and photoluminescence measurements were performed for incident power density 0.04–3 kW cm{sup −2}, lattice temperature 10 K, and forward bias 1.2 V. An order of magnitude photocurrent increase was observed for non-equilibrium hot-carrier temperatures >35 K. This photocurrent activation temperature is consistent with that of equilibrium carriers in a lattice at elevated temperature. The observed hot-carrier photo-current is extracted from the well over an energy selective GaAs barrier, thus integrating two essential components of a hot-carrier solar cell: a hot-carrier absorber and an energy selective contact.

  18. Long dephasing time and high-temperature conductance fluctuations in an open InGaAs quantum dot

    NASA Astrophysics Data System (ADS)

    Hackens, B.; Delfosse, F.; Faniel, S.; Gustin, C.; Boutry, H.; Wallart, X.; Bollaert, S.; Cappy, A.; Bayot, V.

    2002-12-01

    We measure the electron phase-coherence time τφ up to 18 K using universal fluctuations in the low-temperature magnetoconductance of an open InGaAs quantum dot. The temperature dependence of τφ is quantitatively consistent with the two-dimensional model of electron-electron interactions in disordered systems. In our sample, τφ is two to four times larger than previously reported in GaAs quantum dots. We attribute this enhancement to a larger value of the Fermi energy and the lower electron effective mass in our sample. We also observe a distinct type of conductance fluctuation due to ballistic electron focusing inside the dot up to 204 K.

  19. Indium and gallium diffusion through zirconia in the TiN/ZrO{sub 2}/InGaAs stack

    SciTech Connect

    Ceballos-Sanchez, O.; Martinez, E.; Guedj, C.; Veillerot, M.; Herrera-Gomez, A.

    2015-06-01

    Angle-resolved X-ray Photoelectron Spectroscopy (ARXPS) was applied to the TiN/ZrO{sub 2}/InGaAs stack to assess its thermal stability. Through a robust ARXPS analysis, it was possible to observe subtle effects such as the thermally induced diffusion of substrate atomic species (In and Ga) through the dielectric layer. The detailed characterization of the film structure allowed for assessing the depth profiles of the diffused atomic species by means of the scenarios-method. Since the quantification for the amount of diffused material was done at different temperatures, it was possible to obtain an approximate value of the activation energy for the diffusion of indium through zirconia. The result is very similar to the previously reported values for indium diffusion through alumina and through hafnia.

  20. Compact fiber-pigtailed InGaAs photoconductive antenna module for terahertz-wave generation and detection.

    PubMed

    Han, Sang-Pil; Kim, Namje; Ko, Hyunsung; Ryu, Han-Cheol; Park, Jeong-Woo; Yoon, Young-Jong; Shin, Jun-Hwan; Lee, Dong Hun; Park, Sang-Ho; Moon, Seok-Hwan; Choi, Sung-Wook; Chun, Hyang Sook; Park, Kyung Hyun

    2012-07-30

    We propose a compact fiber-pigtailed InGaAs photoconductive antenna (FPP) module having an effective heat-dissipation solution as well as a module volume of less than 0.7 cc. The heat-dissipation of the FPP modules when using a heat-conductive printed circuit board (PCB) and an aluminium nitride (AlN) submount, without any cooling systems, improve by 40% and 85%, respectively, when compared with a photoconductive antenna chip on a conventional PCB. The AlN submount is superior to those previously reported as a heat-dissipation solution. Terahertz time-domain spectroscopy (THz-TDS) using the FPP module perfectly detects the absorption lines of water vapor in free space and an α-lactose sample. PMID:23038394

  1. Comparison of vacancy and antisite defects in GaAs and InGaAs through hybrid functionals.

    PubMed

    Komsa, Hannu-Pekka; Pasquarello, Alfredo

    2012-02-01

    The formation energies and charge transition levels of vacancy and antisite defects in GaAs and In(0.5)Ga(0.5)As are calculated through hybrid density functionals. In As-rich conditions, the As antisite is the most stable defect in both GaAs and InGaAs, except for n-type GaAs for which the Ga vacancy is favored. The Ga antisite shows the lowest formation energy in Ga-rich conditions. The As antisite provides a consistent interpretation of the defect densities measured at mid-gap for both GaAs/oxide and InGaAs/oxide interfaces. PMID:22214854

  2. Identification and thermal stability of the native oxides on InGaAs using synchrotron radiation based photoemission

    NASA Astrophysics Data System (ADS)

    Brennan, B.; Hughes, G.

    2010-09-01

    A high resolution synchrotron radiation core level photoemission study of the native oxides on In0.53Ga0.47As was carried out in order to determine the various oxidation states present on the surface. The thermal stability of the oxidation states was also investigated by annealing the samples in vacuum at temperatures ranging from 150 to 450 °C. As well as the widely reported oxidation states, various arsenic, gallium, and indium oxides, along with mixed phase gallium arsenic and indium gallium oxides are identified. Elemental binary oxides have been identified as residing at the oxide substrate interface and could play an important role in understanding the growth of metal oxide dielectric layers on the InGaAs surface, due to their apparent chemical stability.

  3. Sensitivity and noise of micro-Hall magnetic sensors based on InGaAs quantum wells

    NASA Astrophysics Data System (ADS)

    Chenaud, B.; Segovia-Mera, A.; Delgard, A.; Feltin, N.; Hoffmann, A.; Pascal, F.; Zawadzki, W.; Mailly, D.; Chaubet, C.

    2016-01-01

    We study the room-temperature performance of micro-Hall magnetic sensors based on pseudomorphic InGaAs quantum wells. Active areas of our sensors range from 1 to 80 μm. We focus on the smallest detectable magnetic fields in small sensors and perform a systematic study of noise at room temperature in the frequency range between 1 Hz and 100 kHz. Our data are interpreted by the mobility fluctuation model. The Hooge parameter is determined for the applied technology. We show that, independently of the experimental frequency, the ratio of sensitivity to noise is proportional to characteristic length of the sensor. The resolution of 1 mG/√{Hz } is achievable in a 3 μm sensor at room temperature.

  4. Fermi level pinning in metal/Al2O3/InGaAs gate stack after post metallization annealing

    NASA Astrophysics Data System (ADS)

    Winter, R.; Krylov, I.; Cytermann, C.; Tang, K.; Ahn, J.; McIntyre, P. C.; Eizenberg, M.

    2015-08-01

    The effect of post metal deposition annealing on the effective work function in metal/Al2O3/InGaAs gate stacks was investigated. The effective work functions of different metal gates (Al, Au, and Pt) were measured. Flat band voltage shifts for these and other metals studied suggest that their Fermi levels become pinned after the post-metallization vacuum annealing. Moreover, there is a difference between the measured effective work functions of Al and Pt, and the reported vacuum work function of these metals after annealing. We propose that this phenomenon is caused by charging of indium and gallium induced traps at the annealed metal/Al2O3 interface.

  5. An InGaAs detector based radiation thermometer and fixed-point blackbodies for temperature scale realization at NIM

    SciTech Connect

    Hao, X.; Yuan, Z.; Wang, J.; Lu, X.

    2013-09-11

    In this paper, we describe an InGaAs detector based radiation thermometer (IRT) and new design of fixed-point blackbodies, including Sn, Zn, Al and Cu, for the establishment of a temperature scale from 200 °C to 1085 °C at the National Institute of Metrology of China. The construction and calibration of the IRT with the four fixed-point blackbodies are described. Characteristics of the IRT, such as the size-of-source effect, the amplifier performance and its stability are determined. The design of the four fixed-points, with 10 mm diameter of aperture and 0.9999 emissivity, is described. The uncertainty of the scale realization is elaborated.

  6. An InGaAs detector based radiation thermometer and fixed-point blackbodies for temperature scale realization at NIM

    NASA Astrophysics Data System (ADS)

    Hao, X.; Yuan, Z.; Wang, J.; Lu, X.

    2013-09-01

    In this paper, we describe an InGaAs detector based radiation thermometer (IRT) and new design of fixed-point blackbodies, including Sn, Zn, Al and Cu, for the establishment of a temperature scale from 200 °C to 1085 °C at the National Institute of Metrology of China. The construction and calibration of the IRT with the four fixed-point blackbodies are described. Characteristics of the IRT, such as the size-of-source effect, the amplifier performance and its stability are determined. The design of the four fixed-points, with 10 mm diameter of aperture and 0.9999 emissivity, is described. The uncertainty of the scale realization is elaborated.

  7. Reliability and failure mode investigation of high-power multimode InGaAs strained quantum well single emitters

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Foran, Brendan; Presser, Nathan; Mason, Maribeth; Moss, Steven C.

    2007-02-01

    In recent years record performance characteristics from multi-mode InGaAs strained quantum well single emitters at 920-980nm have been reported including a maximum CW optical output power of ~20W and a power conversion efficiency of ~75%. These excellent performance characteristics are only possible through combined optimization of laser structure design, chip fabrication processes, and packaging. Whereas broad area multi-mode single emitters likely have sufficient reliability for industrial uses, reliability of these lasers still remains a concern for communications applications including deployment in potential space satellite systems where high reliability is required. Most of previous reports on these lasers have been focused on their performance characteristics with very limited reports on failure mode analysis although understanding the physics of failure is crucial in developing a proper lifetime model for these lasers. We thus report on the reliability and failure mode analysis of high power multi-mode single emitters. The lasers studied were broad area strained InGaAs single QW lasers at 940-980nm with typical aperture widths of around 100μm. At an injection current of 7A typical CW output powers were over 6W at 25°C with a wall plug efficiency of ~60%. First, various lasing characteristics were measured including spatial and thermal characteristics that are critical to understanding performance and reliability of these devices. ACC burn-in tests with different stress conditions were performed on these devices until their failure. We report accelerated lifetest results with over 5000 accumulated test hours. Finally, we report failure mode investigation results of the degraded lasers.

  8. Spectral imaging of chemical compounds using multivariate optically enhanced filters integrated with InGaAs VGA cameras

    NASA Astrophysics Data System (ADS)

    Priore, Ryan J.; Jacksen, Niels

    2016-05-01

    Infrared hyperspectral imagers (HSI) have been fielded for the detection of hazardous chemical and biological compounds, tag detection (friend versus foe detection) and other defense critical sensing missions over the last two decades. Low Size/Weight/Power/Cost (SWaPc) methods of identification of chemical compounds spectroscopy has been a long term goal for hand held applications. We describe a new HSI concept for low cost / high performance InGaAs SWIR camera chemical identification for military, security, industrial and commercial end user applications. Multivariate Optical Elements (MOEs) are thin-film devices that encode a broadband, spectroscopic pattern allowing a simple broadband detector to generate a highly sensitive and specific detection for a target analyte. MOEs can be matched 1:1 to a discrete analyte or class prediction. Additionally, MOE filter sets are capable of sensing an orthogonal projection of the original sparse spectroscopic space enabling a small set of MOEs to discriminate a multitude of target analytes. This paper identifies algorithms and broadband optical filter designs that have been demonstrated to identify chemical compounds using high performance InGaAs VGA detectors. It shows how some of the initial models have been reduced to simple spectral designs and tested to produce positive identification of such chemicals. We also are developing pixilated MOE compressed detection sensors for the detection of a multitude of chemical targets in challenging backgrounds/environments for both commercial and defense/security applications. This MOE based, real-time HSI sensor will exhibit superior sensitivity and specificity as compared to currently fielded HSI systems.

  9. Direct Measurements of Fermi Level Pinning at the Surface of Intrinsically n-Type InGaAs Nanowires.

    PubMed

    Speckbacher, Maximilian; Treu, Julian; Whittles, Thomas J; Linhart, Wojciech M; Xu, Xiaomo; Saller, Kai; Dhanak, Vinod R; Abstreiter, Gerhard; Finley, Jonathan J; Veal, Tim D; Koblmüller, Gregor

    2016-08-10

    Surface effects strongly dominate the intrinsic properties of semiconductor nanowires (NWs), an observation that is commonly attributed to the presence of surface states and their modification of the electronic band structure. Although the effects of the exposed, bare NW surface have been widely studied with respect to charge carrier transport and optical properties, the underlying electronic band structure, Fermi level pinning, and surface band bending profiles are not well explored. Here, we directly and quantitatively assess the Fermi level pinning at the surfaces of composition-tunable, intrinsically n-type InGaAs NWs, as one of the prominent, technologically most relevant NW systems, by using correlated photoluminescence (PL) and X-ray photoemission spectroscopy (XPS). From the PL spectral response, we reveal two dominant radiative recombination pathways, that is, direct near-band edge transitions and red-shifted, spatially indirect transitions induced by surface band bending. The separation of their relative transition energies changes with alloy composition by up to more than ∼40 meV and represent a direct measure for the amount of surface band bending. We further extract quantitatively the Fermi level to surface valence band maximum separation using XPS, and directly verify a composition-dependent transition from downward to upward band bending (surface electron accumulation to depletion) with increasing Ga-content x(Ga) at a crossover near x(Ga) ∼ 0.2. Core level spectra further demonstrate the nature of extrinsic surface states being caused by In-rich suboxides arising from the native oxide layer at the InGaAs NW surface. PMID:27458736

  10. Phobos: Observed bulk properties

    NASA Astrophysics Data System (ADS)

    Pätzold, Martin; Andert, Tom; Jacobson, Robert; Rosenblatt, Pascal; Dehant, Véronique

    2014-11-01

    This work is a review of the mass determinations of the Mars moon Phobos by spacecraft close flybys, by solving for the Martian gravity field and by the analysis of secular orbit perturbations. The absolute value and accuracy is sensitive on the knowledge and accuracy of the Phobos ephemeris, of the spacecraft orbit, other perturbing forces acting on the spacecraft and the resolution of the Martian gravity field besides the measurement accuracy of the radio tracking data. The mass value and its error improved from spacecraft mission to mission or from the modern analysis of “old” tracking data but these solutions depend on the accuracy of the ephemeris at the time of observation. The mass value seems to settle within the range of GMPh=(7.11±0.09)×10-4 km3 s-2 which covers almost all mass values from close flybys and “distant” encounters within its 3-σ error (1.5%). Using the volume value determined from MEX HRSC imaging, the bulk density is (1873±31) kg m-3 (3-σ error or 1.7%), a low value which suggests that Phobos is either highly porous, is composed partially of light material or both. The determination of the gravity coefficients C20 and C22 from the Mars Express 2010 close flyby does not allow to draw conclusion on the internal structure. The large errors do not distinguish whether Phobos is homogeneous or not. In view of theories of the Phobos' origin, one possibility is that Phobos is not a captured asteroid but accreted from a debris disk in Mars orbit as a second generation solar system object.

  11. Bulk Data Mover

    2011-01-03

    Bulk Data Mover (BDM) is a high-level data transfer management tool. BDM handles the issue of large variance in file sizes and a big portion of small files by managing the file transfers with optimized transfer queue and concurrency management algorithms. For example, climate simulation data sets are characterized by large volume of files with extreme variance in file sizes. The BDN achieves high performance using a variety of techniques, including multi-thraded concurrent transfer connections,more » data channel caching, load balancing over multiple transfer servers, and storage i/o pre-fetching. Logging information from the BDM is collected and analyzed to study the effectiveness of the transfer management algorithms. The BDM can accept a request composed of multiple files or an entire directory. The request also contains the target site and directory where the replicated files will reside. If a directory is provided at the source, then the BDM will replicate the structure of the source directory at the target site. The BDM is capable of transferring multiple files concurrently as well as using parallel TCP streams. The optimal level of concurrency or parallel streams depends on the bandwidth capacity of the storage systems at both ends of the transfer as well as achievable bandwidth of the wide-area network. Hardware req.-PC, MAC, Multi-platform & Workstation; Software req.: Compile/version-Java 1.50_x or ablove; Type of files: source code, executable modules, installation instructions other, user guide; URL: http://sdm.lbl.gov/bdm/« less

  12. The effect of post oxide deposition annealing on the effective work function in metal/Al{sub 2}O{sub 3}/InGaAs gate stack

    SciTech Connect

    Winter, R.; Krylov, I.; Eizenberg, M.; Ahn, J.; McIntyre, P. C.

    2014-05-19

    The effect of post oxide deposition annealing on the effective work function in metal/Al{sub 2}O{sub 3}/ InGaAs gate stacks was investigated. Using a systematic method for effective work function extraction, a shift of 0.3 ± 0.1 eV was found between the effective work function of forming gas annealed samples and vacuum annealed samples. The electrical measurements enabled us to obtain the band alignment of the metal/Al{sub 2}O{sub 3}/InGaAs gate stack. This band alignment was confirmed by X-ray photoelectron spectroscopy. The measured shift in the effective work function between different annealing ambient may be attributed to indium out-diffusion during post oxide deposition annealing that is observed in forming gas anneal to a much larger extent than in vacuum.

  13. Formation of self-assembled InGaAs quantum dot arrays aligned along quasiperiodic multiatomic steps on vicinal (111)B GaAs

    SciTech Connect

    Akiyama, Y.; Sakaki, H.

    2006-10-30

    Dense and highly ordered arrays of self-assembled InGaAs quantum dots are formed by molecular beam epitaxy along multiatomic steps on vicinal (111)B GaAs. This unique structure has been synthesized by depositing a nominally 3-nm-thick In{sub 0.3}Ga{sub 0.7}As layer onto a periodically corrugated surface prepared on a GaAs substrate tilted 8.5 deg. from (111)B. Each dot is typically 30-50 nm in lateral size and about 4 nm in height. Accumulation and release processes of strains in InGaAs layers deposited on stepped surfaces are discussed to suggest a possible mechanism for the aligned dot formation.

  14. Detailed Study of the Influence of InGaAs Matrix on the Strain Reduction in the InAs Dot-In-Well Structure.

    PubMed

    Wang, Peng; Chen, Qimiao; Wu, Xiaoyan; Cao, Chunfang; Wang, Shumin; Gong, Qian

    2016-12-01

    InAs/InGaAs dot-in-well (DWELL) structures have been investigated with the systematically varied InGaAs thickness. Both the strained buffer layer (SBL) below the dot layer and the strain-reducing layer (SRL) above the dot layer were found to be responsible for the redshift in photoluminescence (PL) emission of the InAs/InGaAs DWELL structure. A linear followed by a saturation behavior of the emission redshift was observed as a function of the SBL and SRL thickness, respectively. The PL intensity is greatly enhanced by applying both of the SRL and SBL. Finite element analysis simulation and transmission electron microscopy (TEM) measurement were carried out to analyze the strain distribution in the InAs QD and the InGaAs SBL. The results clearly indicate the strain reduction in the QD induced by the SBL, which are likely the main cause for the emission redshift. PMID:26932758

  15. The simulation of localized surface plasmon and surface plasmon polariton in wire grid polarizer integrated on InP substrate for InGaAs sensor

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Li, Tao; Shao, Xiumei; Li, Xue; Gong, Haimei

    2015-07-01

    We numerically demonstrate the integration of gold wire grid polarizer on InP substrate for InGaAs polarimetric imaging. The effective spectral range of wire grid polarizer has been designed in 0.8-3 μm according to InGaAs response waveband. The dips in TM transmission are observed due to surface plasmon (SPs) significantly damaging polarization performance. To further understand the coupling mechanism between gold wire grid grating and InP, the different contributions of surface plasmon polariton (SPP) and localized surface plasmon (LSP) to the dips are analyzed. Both transmission and reflectance spectra are simulated at different grating periods and duty cycles by finite-different time-domain (FDTD) method. LSP wavelength is located at around 1 μm and sensitive to the specific shape of metal wire. SPP presents higher resonance wavelength closely related to grating period. The simulations of electric field distribution show the same results.

  16. Low interface defect density of atomic layer deposition BeO with self-cleaning reaction for InGaAs metal oxide semiconductor field effect transistors

    SciTech Connect

    Shin, H. S.; Yum, J. H.; Johnson, D. W.; Harris, H. R.; Hudnall, Todd W.; Oh, J.; Kirsch, P.; Wang, W.-E.; Bielawski, C. W.; Banerjee, S. K.; Lee, J. C.; Lee, H. D.

    2013-11-25

    In this paper, we discuss atomic configuration of atomic layer deposition (ALD) beryllium oxide (BeO) using the quantum chemistry to understand the theoretical origin. BeO has shorter bond length, higher reaction enthalpy, and larger bandgap energy compared with those of ALD aluminum oxide. It is shown that the excellent material properties of ALD BeO can reduce interface defect density due to the self-cleaning reaction and this contributes to the improvement of device performance of InGaAs MOSFETs. The low interface defect density and low leakage current of InGaAs MOSFET were demonstrated using X-ray photoelectron spectroscopy and the corresponding electrical results.

  17. Indium out-diffusion in Al{sub 2}O{sub 3}/InGaAs stacks during anneal at different ambient conditions

    SciTech Connect

    Krylov, Igor; Winter, Roy; Ritter, Dan; Eizenberg, Moshe

    2014-06-16

    Indium out-diffusion during anneal enhances leakage currents in metal/dielectric/InGaAs gate stacks. In this work, we study the influence of ambient conditions during anneal on indium out-diffusion in Al{sub 2}O{sub 3}/InGaAs structures, prior to the gate metal deposition. Using X-ray photoemission spectroscopy and time of flight secondary ions mass spectrometry, we observed much lower indium concentrations in the Al{sub 2}O{sub 3} layer following vacuum and O{sub 2} anneals compared to forming gas or nitrogen anneals. The electrical characteristics of the Ni/Al{sub 2}O{sub 3}/InGaAs gate stack following these pre-metallization anneals as well as after subsequent post metallization anneals are presented. Possible explanations for the role of the annealing ambient conditions on indium out-diffusion are presented.

  18. Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries: Part II. InP, InSb, InGaP and InGaAs

    SciTech Connect

    Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Hobson, W.S.; Jung, K.B.; Lambers, E.S.; Pearton, S.J.; Shul, R.J.

    1998-11-23

    A parametric study of Inductively Coupled Plasma etching of InP, InSb, InGaP and InGaAs has been carried out in IC1/Ar and IBr/Ar chemistries. Etch rates in excess of 3.1 prrdmin for InP, 3.6 prnh-nin for InSb, 2.3 pm/min for InGaP and 2.2 ~rrdmin for InGaAs were obtained in IBr/Ar plasmas. The ICP etching of In-based materials showed a general tendency: the etch rates increased substantially with increasing the ICP source power and rf chuck power in both chemistries, while they decreased with increasing chamber pressure. The IBr/Ar chemistry typically showed higher etch rates than IC1/Ar, but the etched surface mophologies were fairly poor for both chemistries.

  19. Toward a single-chip TECless/NUCless InGaAs SWIR camera with 120-dB intrinsic operation dynamic range

    NASA Astrophysics Data System (ADS)

    Ni, Y.; Arion, B.; Zhu, Y. M.; Potet, P.; Huet, Odile; Reverchon, Jean Luc; Truffer, Jean Patrick; Robo, Jean Alexandre; Costard, Eric

    2011-06-01

    This paper describes a single-chip InGaAs SWIR camera with more than 120dB instant operational dynamic range with an innovative CMOS ROIC technology, so called MAGIC, invented and patented by New Imaging Technologies. A 320x256- pixel InGaAs 25μm pitch photodiode array, designed and fabricated by III-Vlab/Thales Research & Technology(TRT), has been hybridized on this new generation CMOS ROIC. With NIT's MAGIC technology, the sensor's output follows a precise logarithmic law in function of incoming photon flux and gives instant operational dynamic range (DR) better than 120 dB. The ROIC incorporates the entire video signal processing function including a CCIR TV encoder, so a complete SWIR InGaAs camera with standard video output has been realized on a single 30x30 mm2 PCB board with ¼ W power consumption. Neither TEC nor NUC is needed from room temperature operation. The camera can be switched on and off instantly, ideal for all the portable battery operated SWIR band observation applications. The measured RMS noise and FPN noise on the prototype sensor in dark conditions are 0.4 mV and 0.27 mV respectively. The signal excursion from pixel is about 300mV over the 120 dB dynamic range. The FPN remains almost constant over the whole operation dynamic range. The NEI has been measured to be 3,71E+09 ph/s/cm2 with 92 equivalent noise photons at 25Hz frame rate, better than the same architecture of InGaAs photodiode array hybridized on an Indigo ROIC ISC9809 with a pitch of 30 μm for which a readout noise of 120 electrons is observed.

  20. Electrical and optical performance characteristics of 0.74 eV p/n InGaAs monolithic interconnected modules

    SciTech Connect

    Wilt, D.M.; Fatemi, N.S.; Jenkins, P.P.; Weizer, V.G.; Hoffman, R.W. Jr.; Jain, R.K.; Murray, C.S.; Riley, D.R.

    1997-03-01

    There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1cm{sup 2} device consisting of eight series interconnected cells. MIM devices, produced from 0.74 eV InGaAs, have demonstrated V{sub oc}=3.2V , J{sub sc}=70mA/cm{sup 2} and a fill factor of 66{percent} under flashlamp testing. Infrared (IR) reflectance measurements ({gt}2{mu}m) of these devices indicate a reflectivity of {gt}82{percent}. MIM devices produced from 0.55 eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7{percent} AMO) have been demonstrated. {copyright} {ital 1997 American Institute of Physics.}

  1. Passivation of InGaAs(001)-(2 × 4) by Self-Limiting Chemical Vapor Deposition of a Silicon Hydride Control Layer.

    PubMed

    Edmonds, Mary; Kent, Tyler; Chagarov, Evgueni; Sardashti, Kasra; Droopad, Ravi; Chang, Mei; Kachian, Jessica; Park, Jun Hong; Kummel, Andrew

    2015-07-01

    A saturated Si-Hx seed layer for gate oxide or contact conductor ALD has been deposited via two separate self-limiting and saturating CVD processes on InGaAs(001)-(2 × 4) at substrate temperatures of 250 and 350 °C. For the first self-limiting process, a single silicon precursor, Si3H8, was dosed at a substrate temperature of 250 °C, and XPS results show the deposited silicon hydride layer saturated at about 4 monolayers of silicon coverage with hydrogen termination. STS results show the surface Fermi level remains unpinned following the deposition of the saturated silicon hydride layer, indicating the InGaAs surface dangling bonds are electrically passivated by Si-Hx. For the second self-limiting process, Si2Cl6 was dosed at a substrate temperature of 350 °C, and XPS results show the deposited silicon chloride layer saturated at about 2.5 monolayers of silicon coverage with chlorine termination. Atomic hydrogen produced by a thermal gas cracker was subsequently dosed at 350 °C to remove the Si-Cl termination by replacing with Si-H termination as confirmed by XPS, and STS results confirm the saturated Si-Hx bilayer leaves the InGaAs(001)-(2 × 4) surface Fermi level unpinned. Density function theory modeling of silicon hydride surface passivation shows an Si-Hx monolayer can remove all the dangling bonds and leave a charge balanced surface on InGaAs. PMID:26070022

  2. Electrical and optical performance characteristics of 0.74eV p/n InGaAs monolithic interconnected modules

    SciTech Connect

    Wilt, D.M.; Weizer, V.G.; Fatemi, N.S.; Jenkins, P.P.; Hoffman, R.W. Jr.; Jain, R.K.; Murray, C.S.; Riley, D.R.

    1997-06-01

    There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 cm{sup 2} device consisting of eight series interconnected cells. MIM devices, produced from 0.74 eV InGaAs, have demonstrated V{sub oc} = 3.2 volts, J{sub sc} = 70 mA/cm{sup 2} and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurements (> 2 {micro}m) of these devices indicate a reflectivity of > 82%. MIM devices produced from 0.55 eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

  3. Electrical and Optical Performance Characteristics of 0.74-eV p/n InGaAs Monolithic Interconnected Modules

    NASA Technical Reports Server (NTRS)

    Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Jain, Raj K.; Murray, Christopher S.; Riley, David R.

    1997-01-01

    There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74-eV InGaAs, have demonstrated V(sub oc) = 3.2 volts, J(sub sc) = 70 mA/sq cm, and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurements (greater than 2 micron) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55-eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

  4. In-situ atomic layer deposition of tri-methylaluminum and water on pristine single-crystal (In)GaAs surfaces: electronic and electric structures

    NASA Astrophysics Data System (ADS)

    Pi, T. W.; Lin, Y. H.; Fanchiang, Y. T.; Chiang, T. H.; Wei, C. H.; Lin, Y. C.; Wertheim, G. K.; Kwo, J.; Hong, M.

    2015-04-01

    The electronic structure of single-crystal (In)GaAs deposited with tri-methylaluminum (TMA) and water via atomic layer deposition (ALD) is presented with high-resolution synchrotron radiation core-level photoemission and capacitance-voltage (CV) characteristics. The interaction of the precursor atoms with (In)GaAs is confined at the topmost surface layer. The Ga-vacant site on the GaAs(111)A-2 × 2 surface is filled with Al, thereby effectively passivating the As dangling bonds. The As-As dimers on the GaAs(001)-2 × 4 surface are entirely passivated by one cycle of TMA and water. The presumed layerwise deposition fails to happen in GaAs(001)-4 × 6. In In0.20Ga0.80As(001)-2 × 4, the edge row As atoms are partially bonded with the Al, and one released methyl then bonds with the In. It is suggested that the unpassivated surface and subsurface atoms cause large frequency dispersions in CV characteristics under the gate bias. We also found that the (In)GaAs surface is immune to water in ALD. However, the momentary exposure of it to air (less than one minute) introduces significant signals of native oxides. This indicates the necessity of in situ works of high κ/(In)GaAs-related experiments in order to know the precise interfacial atomic bonding and thus know the electronic characteristics. The electric CV measurements of the ALD-Al2O3 on these (In)GaAs surfaces are correlated with their electronic properties.

  5. High-speed InGaAs thin film MSM photodetector characterization using a fiber-based electro-optic sampling system

    NASA Astrophysics Data System (ADS)

    Seo, Sang-Woo; Cho, Sang-Yeon; Huang, Sa; Brown, April; Jokerst, Nan M.

    2004-06-01

    As optoelectronic devices increase in speed, the measurement system used to characterize these devices must have sufficient bandwidth and minimum parasitic loading during test to accurately determine the intrinsic performance of the device under test. Conventional electrical measurement systems have an intrinsic bandwidth due to the available components for test and have parasitic loading due to direct electrical contact to the device under the test. Electro-optic sampling is an excellent measurement technique for characterizing ultra-fast devices because it has high bandwidth, is non-contact, is non-destructive, and relatively non-invasive. In this paper, an optical fiber-based electro-optic sampling system is designed and used for characterizing high speed InGaAs thin film MSM photodetectors. A fiber laser which is operating at 1556 nm wavelength was used for the sampling and excitation beam. Optical fibers were used to connect each component in the system for flexibility. InGaAs thin film MSM photodetectors were fabricated and characterized. InGaAs thin film MSM photodetectors were bonded onto a coplanar strip line deposited on a benzocyclobutene (BCB)-coated glass substrate for characterization. These thin film photodetectors show high speed operation combined with high responsivity and large detection area compared to P-I-N photodetectors operating at similar speeds

  6. Non-destructive mapping of doping and structural composition of MOVPE-grown high current density resonant tunnelling diodes through photoluminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Jacobs, K. J. P.; Stevens, B. J.; Mukai, T.; Ohnishi, D.; Hogg, R. A.

    2015-05-01

    We report on photoluminescence (PL) characterisation of metal-organic vapour phase epitaxy (MOVPE) grown high current density (~700 kA/cm2) InGaAs/AlAs/InP based resonant tunnelling diodes (RTDs) for terahertz emission. The PL mapping we describe allows important information about doping level and uniformity, ternary alloy composition and uniformity, and uniformity of quantum well thickness to be deduced. PL as a function of doping concentration is studied for InGaAs test layers at low temperatures and correlated to secondary-ion mass spectroscopy (SIMS) and electrochemical capacitance-voltage (eCV) profiling to provide non-destructive mapping of doping over the wafer. For the RTD structures, we utilise eCV as a selective etch tool to identify the origin of low temperature PL emission from the quantum well (QW) and the highly doped contact layers. PL mapping of the RTD wafer at low temperatures is shown to allow the assessment of variations in InGaAs alloy composition and QW thickness. Details of the growth process are discussed and confirmed using high resolution X-ray diffraction (HRXRD) crystallography. The rapid non-destructive characterisation and wafer mapping of these structures promises a route to future growth optimisation of such structures.

  7. Dynamic measurement of bulk modulus

    NASA Technical Reports Server (NTRS)

    Dowler, W. L.; Strand, L. D.

    1979-01-01

    Technique based on measuring phase difference between microwave reference and test signals and has been used to determine change in bulk modulus of solid-fuel rocket propellants should be useful in studying other dielectric materials.

  8. Bulk pesticide storage - state perspective

    SciTech Connect

    Buzicky, G.

    1994-12-31

    State bulk pesticide storage regulations continue to evolve differentially due, in large part, to the absence of federal regulations. This is about to change because of the pending promulgation of 40 CFR Part 165, as amended in 1988 by the Environmental Protection Agency (EPA) rules regarding storage, handling and disposal. Until final adoption of the rules by EPA, states continue to address bulk pesticide storage and handling according to individual state statute, rules and guidelines.

  9. Texturing studies on ? bulk crystals

    NASA Astrophysics Data System (ADS)

    Prabhakaran, D.; Subramanian, C.

    1998-08-01

    Textured crystals of 0953-2048/11/8/013/img2 have been grown by the platinum strip heater-floating zone technique. Texturing ratio and phase purity (Bi-2212) of the grown crystals were calculated from the x-ray diffraction data. Chemical compositions of the grown crystals were quantified from the inductively coupled plasma analysis. 0953-2048/11/8/013/img3 was found to be increased by 2 K for a lower level of substitution and a superconductor to semiconductor transition was observed for the higher order Y substitution. Oxygen stoichiometries of the Y substituted crystals were quantified from the iodometry titration method. Micro-twinning along the growth axis was revealed during etching studies for the cleaved crystals.

  10. Current-induced spin polarization in InGaAs epilayers with varying doping densities

    NASA Astrophysics Data System (ADS)

    Luengo-Kovac, Marta; Huang, Simon; Del Gaudio, Davide; Occena, Jordan; Goldman, Rachel; Sih, Vanessa

    Current-induced spin polarization (CISP) is a phenomena in which an applied electric field produces a bulk spin polarization in the plane of the sample. As this is thought to arise from the spin-orbit coupling, it was originally predicted that the magnitude of CISP should be proportional to the spin-orbit (SO) splitting. However, crystal axis-dependent measurements of the CISP and SO fields showed a negative differential relationship between these two quantities. To develop a phenomenological understanding of the factors affecting the magnitude of CISP, we performed measurements on three In0.025Ga0.975As epilayers, Si-doped at 0.67, 9.6, and 14.1 x 1017 cm-3. We will discuss the effects of the doping density and electron mobility on the magnitudes of the SO fields and CISP.

  11. Plasmonic field confinement for separate absorption-multiplication in InGaAs nanopillar avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Farrell, Alan C.; Senanayake, Pradeep; Hung, Chung-Hong; El-Howayek, Georges; Rajagopal, Abhejit; Currie, Marc; Hayat, Majeed M.; Huffaker, Diana L.

    2015-12-01

    Avalanche photodiodes (APDs) are essential components in quantum key distribution systems and active imaging systems requiring both ultrafast response time to measure photon time of flight and high gain to detect low photon flux. The internal gain of an APD can improve system signal-to-noise ratio (SNR). Excess noise is typically kept low through the selection of material with intrinsically low excess noise, using separate-absorption-multiplication (SAM) heterostructures, or taking advantage of the dead-space effect using thin multiplication regions. In this work we demonstrate the first measurement of excess noise and gain-bandwidth product in III-V nanopillars exhibiting substantially lower excess noise factors compared to bulk and gain-bandwidth products greater than 200 GHz. The nanopillar optical antenna avalanche detector (NOAAD) architecture is utilized for spatially separating the absorption region from the avalanche region via the NOA resulting in single carrier injection without the use of a traditional SAM heterostructure.

  12. Modelling of bulk superconductor magnetization

    NASA Astrophysics Data System (ADS)

    Ainslie, M. D.; Fujishiro, H.

    2015-05-01

    This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet-superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed.

  13. Single mode 1.3 μm InGaAs VCSELs for access network applications

    NASA Astrophysics Data System (ADS)

    Westbergh, Petter; Söderberg, Emma; Gustavsson, Johan S.; Modh, Peter; Larsson, Anders; Zhang, Zhenzhong; Berggren, Jesper; Hammar, Mattias

    2008-04-01

    GaAs-based VCSELs emitting near 1.3 μm are realized using highly strained InGaAs quantum wells and a large detuning of the cavity resonance with respect to the gain peak. The VCSELs have an oxide aperture for current and optical confinement and an inverted surface relief for suppression of higher-order transverse modes. The inverted surface relief structure also has the advantage of suppressing oxide modes that otherwise appear in VCSELs with a large detuning between the cavity resonance and the gain peak. Under large signal, digital modulation, clear and open eyes and error free transmission over 9 km of single mode fiber have been demonstrated at the OC-48 and 10 GbE bit rates up to 85°C. Here we review these results and present results from a complementary study of the RF modulation characteristics, including second order harmonic and third order intermodulation distortion, relative intensity noise (RIN), and spurious free dynamic range (SFDR). RIN levels comparable to those of single mode VCSELs emitting at 850 nm are demonstrated, with values from -140 to -150 dB/Hz. SFDR values of 100 and 95 dB•Hz 2/3 were obtained at 2 and 5 GHz, respectively, which is in the range of those required in radio-over-fiber systems.

  14. Study on the Infrared Lens-Free Irradiation Thermometer Based on InGaAs Detector at NIM

    NASA Astrophysics Data System (ADS)

    Hao, X. P.; Yuan, Z. D.; Huang, S. Y.; Song, J.; Xu, K.

    2015-12-01

    A lens-free irradiation thermometer (LF-IRRT) designed for laboratory applications, with 1.55 \\upmu m center wavelength based on the InGaAs detector, and a temperature range from 300° C to 1000° C, has been developed at NIM of China. The thermometer has no imaging optics for collecting the radiation, for which a major benefit is improved stability compared to other radiation thermometers. This paper introduces the measurement principle, the structure of the LF-IRRT, the multiple-point calibration method, and the stability and expanded uncertainty of the thermometer. The stability of the LF-IRRT is better than 0.070° C at temperatures from 300° C to 1000° C over a period of 1 month. The expanded uncertainty is less than 0.20° C for temperatures between 300° C and 1000° C. The size-of-source effect of the LF-IRRT is 0.6 % from the source diameter range from 10 mm to 65 mm.

  15. Reliability and performance of InGaAs broad-area lasers emitting between 910 and 980 nm

    NASA Astrophysics Data System (ADS)

    Zou, Yao; Zucker, Erik P.; Uppal, Kushant; Coblentz, Debbie L.; Liang, Pamela X.; Peters, Matthew G.; Craig, Richard R.

    2001-05-01

    High power InGaAs multi-mode broad area semiconductor lasers emitting between 190 nm and 980 nm are required as optical pumps for Er+ and Yb+ doped double clad fiber lasers and amplifiers. In this paper, we present performance and reliability of two generations of 100 micrometer aperture broad area devices emitting at 920 nm and 970 nm. The first generation devices have been deployed in the field with up to 2.5 W ex-facet optical power. More than 500,000 device-hrs of actual multi-cell lifetest data, and nearly 100 million accelerated device-hrs have been accumulated with 91FIT at 1.2W and 25 degrees Celsius or 1.9 million hrs MTBF at 2W and 25 degrees Celsius. A next-generation design further reduces thermal resistance, optical loss, and far-field divergence resulting in up to 4W ex-facet CW output power with superb reliability. Multi-mode fiber coupled modules demonstrate high coupling efficiency due to the reduced divergence angles of the new design. Lifetest of the new generation devices demonstrate the reliability of 167 FIT at 2W and 25 degrees Celsius or 499,000 hrs MTBF at 4W and 25 degrees Celsius.

  16. A low noise low power 512×256 ROIC for extended wavelength InGaAs FPA

    NASA Astrophysics Data System (ADS)

    Huang, Songlei; Huang, Zhangcheng; Chen, Yu; Li, Tao; Fang, Jiaxiong

    2015-05-01

    A low noise low power 512×256 readout integrated circuit (ROIC) based on Capacitance Trans-impedance Amplifier (CTIA) was designed in this paper. The ROIC with 30μm pixel-pitch and 70 fF integrated capacitance as normal structure and test structure capacitance from 5 to 60 fF, was fabricated in 0.5μm DPTM CMOS process. The results showed that output voltage was larger than 2.0V and power consumption was about 150mW, output ROIC noise was about 3.6E-4V which equivalent noise was 160e-, and the test structure noise was from 20e- to 140 e-. Compared the readout noises in Integration Then Readout (ITR) mode and Integration While Readout (IWR) mode, it indicated that in IWR mode, readout noise comes mainly from both integration capacitance and sampling capacitance, while in ITR mode, readout noise comes mostly from sampling capacitance. Finally the ROIC was flip-chip bonded with Indium bumps to extended wavelength InGaAs detectors with cutoff wavelength 2.5μm at 200K. The peak detectivity exceeded 5E11cmHz1/2/w with 70nA/cm2 dark current density at 200K.

  17. Gallium Arsenide Layers Grown by Molecular Beam Epitaxy on Single Crystalline Germanium Islands on Insulator

    NASA Astrophysics Data System (ADS)

    Takai, Mikio; Tanigawa, Takaho; Minamisono, Tadanori; Gamo, Kenji; Namba, Susumu

    1984-05-01

    Gallium arsenide (GaAs) layers have successfully been grown by molecular beam epitaxy on single crystalline germanium (Ge) islands, recrystallized by zone melting with SiO2 capping layers, on thermally-oxidized Si-wafers. The GaAs layers, grown on the single crystalline Ge islands, show smooth surfaces without any grain-boundaries, while those, grown on the Ge islands with grain-boundaries and on the SiO2, have grain-boundaries. The GaAs layers on the single crystalline Ge islands emit photoluminescence, the intensity of which is almost comparable to that of GaAs layers on bulk Ge crystals.

  18. Diffused P+-N solar cells in bulk GaAs

    NASA Technical Reports Server (NTRS)

    Borrego, J. M.; Ghandhi, S. K.

    1982-01-01

    Recently melt grown GaAs, made by liquid encapsulation techniques, has become available. This material is of sufficiently good quality to allow the fabrication of solar cells by direct diffusion. Results obtained with p(+)/n junction solar cells made by zinc diffusion are described. The quality of bulk GaAs for this application is evaluated.

  19. Growth of bulk single crystals of organic materials for nonlinear optical devices - An overview

    NASA Technical Reports Server (NTRS)

    Penn, Benjamin G.; Cardelino, Beatriz H.; Moore, Craig E.; Shields, Angela W.; Frazier, D. O.

    1991-01-01

    Highly perfect single crystals of nonlinear optical organic materials are required for use in optical devices. An overview of the bulk crystal growth of these materials by melt, vapor, and solution processes is presented. Additionally, methods that may be used to purify starting materials, detect impurities at low levels, screen materials for crystal growth, and process grown crystals are discussed.

  20. Recent developments of film bulk acoustic resonators

    NASA Astrophysics Data System (ADS)

    Gao, Junning; Liu, Guorong; Li, Jie; Li, Guoqiang

    2016-06-01

    Film bulk acoustic wave resonator (FBAR) experienced skyrocketing development in the past 15 years, owing to the explosive development of mobile communication. It stands out in acoustic filters mainly because of high quality factor, which enables low insertion loss and sharp roll off. Except for the massive application in wireless communication, FBARs are also promising sensors because of the high sensitivity and readily integration ability to miniaturize circuits. On the ground of summarizing FBAR’s application in wireless communication as filters and in sensors including electronic nose, bio field, and pressure sensing, this paper review the main challenges of each application faced. The number of filters installed in the mobile phone has being grown explosively, which leads to overcrowded bands and put harsh requirements on component size and power consumption control for each unit. Data flow and rate are becoming increasingly demanding as well. This paper discusses three promising technical strategies addressing these issues. Among which coupled resonator filter is given intense attention because it is able to vigorously reduce the filter size by stacking two or more resonators together, and it is a great technique to increase data flow and rate. Temperature compensation methods are discussed considering their vital influence on frequency stability. Finally, materials improvement and novel materials exploration for band width modulation, tunable band acquisition, and quality factor improvement are discussed. The authors appeal attention of the academic society to bring AlN epitaxial thin film into the FBAR fabrication and have proposed a configuration to implement this idea.

  1. InP/InGaAs/InP DHBT structures with high carbon-doped base grown by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Teng, Teng; Xu, Anhuai; Ai, Likun; Sun, Hao; Qi, Ming

    2013-09-01

    A new InP/InGaAs/InP DHBT structure with high carbon (C)-doped base was optimized and grown successfully by gas source molecular beam epitaxy (GSMBE) in this work. The C-doping concentration is 3×1019 cm-3 with carrier mobility of 66.3 cm2/V s. Characteristics of C-doped InGaAs materials were investigated. High quality InP/InGaAs/InP DHBT structural materials were obtained. The InP/InGaAs/InP DHBT device with emitter area of 100×100 μm2 was fabricated. The open base breakdown voltage (VBCEO) of 4.2 V and current gain of 60 at VCE of 3.0 V were achieved. All these results prove the material is suitable for DHBT device fabrication.

  2. Hanle effect in (In,Ga)As quantum dots: Role of nuclear spin fluctuations

    NASA Astrophysics Data System (ADS)

    Kuznetsova, M. S.; Flisinski, K.; Gerlovin, I. Ya.; Ignatiev, I. V.; Kavokin, K. V.; Verbin, S. Yu.; Yakovlev, D. R.; Reuter, D.; Wieck, A. D.; Bayer, M.

    2013-06-01

    The role of nuclear spin fluctuations in the dynamic polarization of nuclear spins by electrons is investigated in (In,Ga)As/GaAs quantum dots. The photoluminescence polarization under circularly polarized optical pumping in transverse magnetic fields (Hanle effect) is studied. A weak additional magnetic field parallel to the optical axis is used to control the efficiency of nuclear spin cooling and the sign of nuclear spin temperature. The shape of the Hanle curve is drastically modified when changing this control field, as observed earlier in bulk semiconductors and quantum wells. However, the standard nuclear spin cooling theory, operating with the mean nuclear magnetic field (Overhauser field), fails to describe the experimental Hanle curves in a certain range of control fields. This controversy is resolved by taking into account the nuclear spin fluctuations owed to the finite number of nuclei in the quantum dot. We propose a model considering cooling of the nuclear spin system by electron spins experiencing fast vector precession in the random Overhauser fields of nuclear spin fluctuations. The model allows us to accurately describe the measured Hanle curves and to evaluate the parameters of the electron-nuclear spin system of the studied quantum dots.

  3. Plasmonic field confinement for separate absorption-multiplication in InGaAs nanopillar avalanche photodiodes.

    PubMed

    Farrell, Alan C; Senanayake, Pradeep; Hung, Chung-Hong; El-Howayek, Georges; Rajagopal, Abhejit; Currie, Marc; Hayat, Majeed M; Huffaker, Diana L

    2015-01-01

    Avalanche photodiodes (APDs) are essential components in quantum key distribution systems and active imaging systems requiring both ultrafast response time to measure photon time of flight and high gain to detect low photon flux. The internal gain of an APD can improve system signal-to-noise ratio (SNR). Excess noise is typically kept low through the selection of material with intrinsically low excess noise, using separate-absorption-multiplication (SAM) heterostructures, or taking advantage of the dead-space effect using thin multiplication regions. In this work we demonstrate the first measurement of excess noise and gain-bandwidth product in III-V nanopillars exhibiting substantially lower excess noise factors compared to bulk and gain-bandwidth products greater than 200 GHz. The nanopillar optical antenna avalanche detector (NOAAD) architecture is utilized for spatially separating the absorption region from the avalanche region via the NOA resulting in single carrier injection without the use of a traditional SAM heterostructure. PMID:26627932

  4. Photoexcited-induced sensitivity of InGaAs surface QDs to environment.

    PubMed

    Milla, M J; Ulloa, J M; Guzmán, A

    2014-11-01

    A detailed analysis of the impact of illumination on the electrical response of In0.5Ga0.5As surface nanostructures is carried out as a function of different relative humidity conditions. The importance of the surface-to-volume ratio for sensing applications is once more highlighted. From dark-to-photo conditions, the sheet resistance (SR) of a three-dimensional In0.5Ga0.5As nanostructure decays two orders of magnitude compared with that of a two-dimensional nanostructure. The electrical response is found to be vulnerable to the energy of the incident light and the external conditions. Illuminating with high energy light translates into an SR reduction of one order of magnitude under humid atmospheres, whereas it remains nearly unchanged under dry environments. Conversely, lighting with energy below the bulk energy bandgap, shows a negligible effect on the electrical properties regardless the local moisture. Both illumination and humidity are therefore needed for sensing. Photoexcited carriers can only contribute to conductivity if surface states are inactive due to water physisorption. The strong dependence of the electrical response on the environment makes these nanostructures very suitable for the development of highly sensitive and efficient sensing devices. PMID:25325146

  5. Plasmonic field confinement for separate absorption-multiplication in InGaAs nanopillar avalanche photodiodes

    PubMed Central

    Farrell, Alan C.; Senanayake, Pradeep; Hung, Chung-Hong; El-Howayek, Georges; Rajagopal, Abhejit; Currie, Marc; Hayat, Majeed M.; Huffaker, Diana L.

    2015-01-01

    Avalanche photodiodes (APDs) are essential components in quantum key distribution systems and active imaging systems requiring both ultrafast response time to measure photon time of flight and high gain to detect low photon flux. The internal gain of an APD can improve system signal-to-noise ratio (SNR). Excess noise is typically kept low through the selection of material with intrinsically low excess noise, using separate-absorption-multiplication (SAM) heterostructures, or taking advantage of the dead-space effect using thin multiplication regions. In this work we demonstrate the first measurement of excess noise and gain-bandwidth product in III–V nanopillars exhibiting substantially lower excess noise factors compared to bulk and gain-bandwidth products greater than 200 GHz. The nanopillar optical antenna avalanche detector (NOAAD) architecture is utilized for spatially separating the absorption region from the avalanche region via the NOA resulting in single carrier injection without the use of a traditional SAM heterostructure. PMID:26627932

  6. Bulk charges in eleven dimensions

    NASA Astrophysics Data System (ADS)

    Hawking, S. W.; Taylor-Robinson, M. M.

    1998-07-01

    Eleven dimensional supergravity has electric type currents arising from the Chern-Simon and anomaly terms in the action. However the bulk charge integrates to zero for asymptotically flat solutions with topological trivial spatial sections. We show that by relaxing the boundary conditions to generalisations of the ALE and ALF boundary conditions in four dimensions one can obtain static solutions with a bulk charge. Solutions involving anomaly terms preserve between 1/16 and 1/4 of the supersymmetries but Chern-Simons fluxes generally break all of the remaining supersymmetry. One can introduce membranes with the same sign of charge into these backgrounds. This raises the possibility that these generalized membranes might decay quantum mechanically to leave just a bulk distribution of charge. Alternatively and more probably, a bulk distribution of charge can decay into a collection of singly charged membranes. Dimensional reductions of these solutions lead to novel representations of extreme black holes in four dimensions with up to four charges. We discuss how the eleven-dimensional Kaluza-Klein monopole wrapped around a space with non-zero first Pontryagin class picks up an electric charge proportional to the Pontryagin number.

  7. REL - English Bulk Data Input.

    ERIC Educational Resources Information Center

    Bigelow, Richard Henry

    A bulk data input processor which is available for the Rapidly Extensible Language (REL) English versions is described. In REL English versions, statements that declare names of data items and their interrelationships normally are lines from a terminal or cards in a batch input stream. These statements provide a convenient means of declaring some…

  8. Hanford Bulk Vitrification Technology Status

    SciTech Connect

    Witwer, Keith S.; Dysland, Eric J.; Bagaasen, Larry M.; Schlahta, Stephan N.; Kim, Dong-Sang; Schweiger, Michael J.; Hrma, Pavel R.

    2007-01-25

    Research and testing was initiated in 2003 to support the selection of a supplemental treatment technology for Hanford low-activity wastes (LAWs). AMEC’s bulk vitrification process was chosen for full-scale demonstration, and the Demonstration Bulk Vitrification System (DBVS) project was started in 2004. Also known as in-container vitrification™ (ICV™), the bulk vitrification process combines soil, liquid LAW, and additives (B2O3 and ZrO2); dries the mixture; and then vitrifies the material in a batch feed-while-melt process in a refractory lined steel container. The DBVS project was initiated with the intent to engineer, construct, and operate a full-scale bulk vitrification pilot-plant to treat LAW from Tank 241-S-109 at the U.S. Department of Energy (DOE) Hanford Site. AMEC is adapting its ICV™ technology for this application with technical and analytical support from Pacific Northwest National Laboratory (PNNL). The DBVS project is funded by the DOE Office of River Protection and administered by CH2M HILL Hanford Group, Inc. Since the beginning of the selection process in 2003, testing has utilized crucible-scale, engineering-scale, and full-scale bulk vitrification equipment. Crucible-scale testing, coupled with engineering-scale testing, helps establish process limitations of selected glass formulations. Full-scale testing provides critical design verification of the ICV™ process both before and during operation of the demonstration facility. Initial testing focused on development and validation of the baseline equipment configuration and glass formulation. Subsequent testing was focused on improvements to the baseline configuration. Many improvements have been made to the bulk vitrification system equipment configuration and operating methodology since its original inception. Challenges have been identified and met as part of the parallel testing and design process. A 100% design package for the pilot plant is complete and has been submitted to DOE

  9. InGaAs inversion layers band structure, electrostatics, and mobility modeling based on 8 band k → · p → theory

    NASA Astrophysics Data System (ADS)

    Pham, Anh-Tuan; Jin, Seonghoon; Choi, Woosung; Lee, Myoung-Jae; Cho, Seong-Ho; Kim, Young-Tae; Lee, Keun-Ho; Park, Youngkwan

    2015-11-01

    8 band k → · p → method is used to calculate subband structures of InGaAs inversion layers accounting for strong coupling between conduction and valence bands around Γ point as well as quantum confinement. Inversion layer mobility is computed employing Kubo-Greenwood formalism. Scatterings due to acoustic phonons, polar optical phonons, ionized impurities, interface fixed charges, surface roughness, and alloy disorder are included. The simulated low-field electron mobility results are in good agreement with experimental data with and without an InP capping layer.

  10. Controlling Planar and Vertical Ordering in Three-Dimensional (In,Ga)As Quantum Dot Lattices by GaAs Surface Orientation

    SciTech Connect

    Schmidbauer, M.; Seydmohamadi, Sh.; Wang, Zh.M.; Mazur, Yu.I.; Salamo, G.J.; Grigoriev, D.; Schaefer, P.; Koehler, R.; Hanke, M.

    2006-02-17

    Anisotropic surface diffusion and strain are used to explain the formation of three-dimensional (In,Ga)As quantum dot lattices. The diffusion characteristics of the surface, coupled with the elastic anisotropy of the matrix, provides an excellent opportunity to influence the dot positions. In particular, quantum dots that are laterally organized into long chains or chessboard two-dimensional arrays vertically organized with strict vertical ordering or vertical ordering that is inclined to the sample surface normal are accurately predicted and observed.

  11. Protein Crystals Grown in Space

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A collage of protein and virus crystals, many of which were grown on the U.S. Space Shuttle or Russian Space Station, Mir. The crystals include the proteins canavalin; mouse monoclonal antibody; a sweet protein, thaumatin; and a fungal protease. Viruses are represented here by crystals of turnip yellow mosaic virus and satellite tobacco mosaic virus. The crystals are photographed under polarized light (thus causing the colors) and range in size from a few hundred microns in edge length up to more than a millimeter. All the crystals are grown from aqueous solutions and are useful for X-ray diffraction analysis. Credit: Dr. Alex McPherson, University of California, Irvine.

  12. Evaluation of InGaAs 640×512 detector array manufactured by Chunghwa Leading Photonics Tech

    NASA Astrophysics Data System (ADS)

    Nagayama, Takahiro; Takeuchi, Nami; Kokusho, Takuma; Yamanaka, Asa; Nishiyama, Miho; Kaneda, Hidehiro

    2014-07-01

    Focal Plane Arrays (FPA) are key items for modern astronomical observations in the near infrared wavelength, but it is very expensive and not easy to get them. Less expensive NIR FPAs with reasonable performance are very important to spread NIR observation extensively. FPA640×512 manufactured by Chunghwa Leading Photonics Tech is a 640×512 InGaAs detector covering the 0.9-1.7 μm wavelength. Since this array is significantly cheaper than the commonly used NIR FPAs in the astronomical observation, it is possible to be a good choice for particular projects which do not need many pixels, if FPA640×512 has acceptable performance for the purpose. We have evaluated one test grade array of FPA640×512 both in the room and low temperature environment. In order to evaluate the characteristics of this FPA in the low temperature environment, we cooled it down by the mechanical refrigerator and confirmed that it works at 100 K. We have found that the dark current reduces exponentially as the FPA temperature decreases, but it hits the bottom at~1000 e-/sec bellow 200 K with the default setting. We are trying to reduce the dark current by optimizing the bias voltage and the current to the MUX circuit. The latest experiments have shown the possibility that the dark current decreases to~200 e-/sec. This value is still higher than that of NIR FPAs used in the scientific observation, but it may be applicable for the particular purpose, for example, FPAs for slit viewer in spectrometers, wave front sensor, and so on.

  13. High-Performance Wrap-Gated InGaAs Nanowire Field-Effect Transistors with Sputtered Dielectrics

    PubMed Central

    Shen, Li-Fan; Yip, SenPo; Yang, Zai-xing; Fang, Ming; Hung, TakFu; Pun, Edwin Y.B.; Ho, Johnny C.

    2015-01-01

    Although wrap-gated nanowire field-effect-transistors (NWFETs) have been explored as an ideal electronic device geometry for low-power and high-frequency applications, further performance enhancement and practical implementation are still suffering from electron scattering on nanowire surface/interface traps between the nanowire channel and gate dielectric as well as the complicated device fabrication scheme. Here, we report the development of high-performance wrap-gated InGaAs NWFETs using conventional sputtered Al2O3 layers as gate dielectrics, instead of the typically employed atomic layer deposited counterparts. Importantly, the surface chemical passivation of NW channels performed right before the dielectric deposition is found to significantly alleviate plasma induced defect traps on the NW channel. Utilizing this passivation, the wrap-gated device exhibits superior electrical performances: a high ION/IOFF ratio of ~2 × 106, an extremely low sub-threshold slope of 80 mV/decade and a peak field-effect electron mobility of ~1600 cm2/(Vs) at VDS = 0.1 V at room temperature, in which these values are even better than the ones of state-of-the-art NWFETs reported so far. By combining sputtering and pre-deposition chemical passivation to achieve high-quality gate dielectrics for wrap-gated NWFETs, the superior gate coupling and electrical performances have been achieved, confirming the effectiveness of our hybrid approach for future advanced electronic devices. PMID:26607169

  14. Low-noise, fast frame-rate InGaAs 320 x 256 FPA for hyperspectral applications

    NASA Astrophysics Data System (ADS)

    Vermeiren, Jan; Van Bogget, Urbain; Van Horebeek, Guido; Bentell, Jonas; Verbeke, Peet; Colin, Thierry

    2009-05-01

    InGaAs is the material of preference for uncooled imaging in the [0.9-1.7 μm] SWIR range, as it can be manufactured on low cost InP substrates in a mainstream technology for optical telecommunications. By removing the substrate the spectral range can be extended to the [0.6 - 1.7 μm] range. In this way low cost, room temperature operated FPAs cameras for imaging and hyperspectral applications can be developed. The FPA is built around a low power CTIA stage with 3 S&H capacitors in the 20*20 um2 unit cell. This approach results in a synchronous shutter operation, which will support both ITR and IWR operation. In IWR mode the integration dead time is limited to max. 10 μsec. The CDS operation yields in a high sensitivity combined with a low noise: This presentation will focus on the development of a 20 μm pitch 320*256 device, with the following main characteristics: 20 μV/e-sensitivity and < 60 e-noise. The 4 low-power, differential outputs are enabling to drive an output load of > 30 pF at 40 Msamples/sec each, resulting in a > 1700 Hz frame rate, while at the same time the overall nominal power dissipation is < 200 mW. The ROIC is realized in a 0.35 um technology and the outputs are designed to drive directly a 3.3 V, 1.5 V VCM differential AD convertor. The circuit also supports a NDR operating mode to further reduce the noise of the FPA. A small from factor camera with Cameralink output is built around this FPA.

  15. AC and DC transport currents in melt-grown YBCO

    SciTech Connect

    Yi, Z.; Ashworth, S.; Becluz, C.; Scurlock, R.G. )

    1991-03-01

    It has been suggested that the transport J{sub c} in multi-grain samples of bulk YBCO are limited by the intergrain links. This paper reports on preliminary measurements of intergrain currents. The intergrain critical currents in melt grown YBCO do not appear to be as sensitive to the precise crystallographic alignment of adjacent grains a has been reported for thin films. The measured critical current of similar grain boundaries varies widely, between 15000 A/cm{sup 2} and 200A/Cm{sub 2} for adjacent boundaries in the same sample.

  16. Growth and Characteristics of Bulk Single Crystals Grown from Solution on Earth and in Microgravity

    NASA Technical Reports Server (NTRS)

    Aggarwal, M. D.; Batra, A. K.; Lal, R. B.; Penn, Benjamin G.; Frazier, Donald O.

    2011-01-01

    The growth of crystals has been of interest to physicists and engineers for a long time because of their unique properties. Single crystals are utilized in such diverse applications as pharmaceuticals, computers, infrared detectors, frequency measurements, piezoelectric devices, a variety of high technology devices and sensors. Solution crystal growth is one of the important techniques to grow a variety of crystals when the material decomposes at the melting point and a suitable solvent is available to make a saturated solution at a desired temperature. In this chapter an attempt is made to give some fundamentals of growing crystals from solution including improved designs of various crystallizers. Since the same solution crystal growth technique could not be used in microgravity, authors had proposed a new cooled sting technique to grow crystals in space. Authors? experiences of conducting two space shuttle experiments relating to solution crystal growth are also detailed in this work. The complexity of these solution growth experiments to grow crystals in space are discussed. These happen to be some of the early experiments performed in space, and various lessons learned are described. A brief discussion of protein crystal growth that also shares basic principles of solution growth technique is given along with some flight hardware information for its growth in microgravity.

  17. Diffusion length measurements in bulk and epitaxially grown 3-5 semiconductors using charge collection microscopy

    NASA Technical Reports Server (NTRS)

    Leon, R. P.

    1987-01-01

    Diffusion lengths and surface recombination velocities were measured in GaAs diodes and InP finished solar cells. The basic techniques used was charge collection microscopy also known as electron beam induced current (EBIC). The normalized currents and distances from the pn junction were read directly from the calibrated curves obtained while using the line scan mode in an SEM. These values were then equated to integral and infinite series expressions resulting from the solution of the diffusion equation with both extended generation and point generation functions. This expands previous work by examining both thin and thick samples. The surface recombination velocity was either treated as an unknown in a system of two equations, or measured directly using low e(-) beam accelerating voltages. These techniques give accurate results by accounting for the effects of surface recombination and the finite size of the generation volume.

  18. A direct comparison of CVD-grown and exfoliated MoS2 using optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Plechinger, G.; Mann, J.; Preciado, E.; Barroso, D.; Nguyen, A.; Eroms, J.; Schüller, C.; Bartels, L.; Korn, T.

    2014-06-01

    MoS2 is a highly interesting material, which exhibits a crossover from an indirect band gap in the bulk crystal to a direct gap for single layers. Here, we perform a direct comparison between large-area MoS2 films grown by chemical vapor deposition (CVD) and MoS2 flakes prepared by mechanical exfoliation from mineral bulk crystal. Raman spectroscopy measurements show differences between the in-plane and out-of-plane phonon mode positions in CVD-grown and exfoliated MoS2. Photoluminescence (PL) mapping reveals large regions in the CVD-grown films that emit strong PL at room-temperature, and low-temperature PL scans demonstrate a large spectral shift of the A exciton emission as a function of position. Polarization-resolved PL measurements under near-resonant excitation conditions show a strong circular polarization of the PL, corresponding to a valley polarization.

  19. Bulk Crystal Growth of Nonlinear Optical Organic Materials Using Inverted Vertical Gradient Freeze Method

    NASA Technical Reports Server (NTRS)

    Choi, J.; Cruz, Magda; Metzl, R.; Wang, W. S.; Aggarwal, M. D.; Penn, Benjamin G.; Frazier, Donald O.

    1998-01-01

    A new process for producing large bulk single crystals of benzil (C6H5COCOC6H5) is reported in this paper. Good quality crystals have been successfully grown using this approach to crystal growth. This method seems to be very promising for other thermally stable NLO organic materials also. The entire contents vycor crucible 1.5 inch in diameter and 2 inch deep was converted to single crystal. Purity of the starting growth material is also an important factor in the final quality of the grown crystals. The entire crystal can be very easily taken out of the crucible by simple maneuvering. Initial characterization of the grown crystals indicated that the crystals are as good as other crystals grown by conventional Bridgman Stockbarger technique.

  20. Longitudinal bulk acoustic mass sensor

    SciTech Connect

    Hales, J. H.; Teva, J.; Boisen, A.; Davis, Z. J.

    2009-07-20

    A polycrystalline silicon longitudinal bulk acoustic cantilever is fabricated and operated in air at 51 MHz. A mass sensitivity of 100 Hz/fg (1 fg=10{sup -15} g) is obtained from the preliminary experiments where a minute mass is deposited on the device by means of focused ion beam. The total noise in the currently applied measurement system allows for a minimum detectable mass of 0.5 fg in air.

  1. Bulk Superconductors in Mobile Application

    NASA Astrophysics Data System (ADS)

    Werfel, F. N.; Delor, U. Floegel-; Rothfeld, R.; Riedel, T.; Wippich, D.; Goebel, B.; Schirrmeister, P.

    We investigate and review concepts of multi - seeded REBCO bulk superconductors in mobile application. ATZ's compact HTS bulk magnets can trap routinely 1 T@77 K. Except of magnetization, flux creep and hysteresis, industrial - like properties as compactness, power density, and robustness are of major device interest if mobility and light-weight construction is in focus. For mobile application in levitated trains or demonstrator magnets we examine the performance of on-board cryogenics either by LN2 or cryo-cooler application. The mechanical, electric and thermodynamical requirements of compact vacuum cryostats for Maglev train operation were studied systematically. More than 30 units are manufactured and tested. The attractive load to weight ratio is more than 10 and favours group module device constructions up to 5 t load on permanent magnet (PM) track. A transportable and compact YBCO bulk magnet cooled with in-situ 4 Watt Stirling cryo-cooler for 50 - 80 K operation is investigated. Low cooling power and effective HTS cold mass drives the system construction to a minimum - thermal loss and light-weight design.

  2. X ray photoelectron analysis of oxide-semiconductor interface after breakdown in Al{sub 2}O{sub 3}/InGaAs stacks

    SciTech Connect

    Shekhter, P.; Palumbo, F.; Cohen Weinfeld, K.; Eizenberg, M.

    2014-09-08

    In this work, the post-breakdown characteristics of metal gate/Al{sub 2}O{sub 3}/InGaAs structures were studied using surface analysis by x ray photoelectron spectroscopy. The results show that for dielectric breakdown under positive bias, localized filaments consisting of oxidized substrate atoms (In, Ga and As) were formed, while following breakdown under negative bias, a decrease of oxidized substrate atoms was observed. Such differences in the microstructure at the oxide-semiconductor interface after breakdown for positive and negative voltages are explained by atomic diffusion of the contact atoms into the gate dielectric in the region of the breakdown spot by the current induced electro-migration effect. These findings show a major difference between Al{sub 2}O{sub 3}/InGaAs and SiO{sub 2}/Si interfaces, opening the way to a better understanding of the breakdown characteristics of III-V complementary-metal-oxide-semiconductor technology.

  3. Comparison of the degradation characteristics of AlON/InGaAs and Al2O3/InGaAs stacks

    NASA Astrophysics Data System (ADS)

    Palumbo, F.; Krylov, I.; Eizenberg, M.

    2015-03-01

    In this paper, the degradation characteristics of MOS (Metal-Oxide-Semiconductor) stacks with Al2O3/AlON or Al2O3 only as dielectric layers on InGaAs were studied. The dielectric nitrides are proposed as possible passivation layers to prevent InGaAs oxidation. At negative bias, it has been found out that the main contribution to the overall degradation of the gate oxide is dominated by the generation of positive charge in the gate oxide. This effect is pronounced in MOS stacks with Al2O3/AlON as dielectric, where we think the positive charge is mainly generated in the AlON interlayer. At positive bias, the degradation is dominated by buildup of negative charge due to electron trapping in pre-existing or stress-induced traps. For stress biases where the leakage currents are low, the changes in the electrical characteristics are dominated by electron-trapping into traps located in energy levels in the upper part of the semiconductor gap. For stress biases with higher leakage current levels, the electron trapping occurs in stress-induced traps increasing the shift of VFB towards positive bias. The overall results clearly show that the improvement of the high-k dielectric/InGaAs interface by introducing N into the Al-oxide does not necessarily mean an increase in the reliability of the MOS stack.

  4. High-optical-power handling InGaAs photodiodes and balanced receivers for high-spurious free dynamic range (SFDR) analog photonic links

    NASA Astrophysics Data System (ADS)

    Joshi, Abhay M.; Wang, Xinde; Mohr, Dan; Becker, Donald; Patil, Ravikiran

    2004-08-01

    We have developed 20 mA or higher photocurrent handling InGaAs photodiodes with 20 GHz bandwidth, and 10 mA or higher photocurrent handling InGaAs photodiodes with >40 GHz bandwidth. These photodiodes have been thoroughly tested for reliability including Bellcore GR 468 standard and are built to ISO 9001:2000 Quality Management System. These Dual-depletion InGaAs/InP photodiodes are surface illuminated and yet handle such large photocurrent due to advanced band-gap engineering. They have broad wavelength coverage from 800 nm to 1700 nm, and thus can be used at several wavelengths such as 850 nm, 1064 nm, 1310 nm, 1550 nm, and 1620 nm. Furthermore, they exhibit very low Polarization Dependence Loss of 0.05dB typical to 0.1dB maximum. Using above high current handling photodiodes, we have developed classical Push-Pull pair balanced photoreceivers for the 2 to 18 GHz EW system. These balanced photoreceivers boost the Spurious Free Dynamic Range (SFDR) by almost 3 dB by eliminating the laser RIN noise. Future research calls for designing an Avalanche Photodiode Balanced Pair to boost the SFDR even further by additional 3 dB. These devices are a key enabling technology in meeting the SFDR requirements for several DoD systems.

  5. Bulk nucleation and growth of inorganic nanowires and nanotubes

    NASA Astrophysics Data System (ADS)

    Sharma, Shashank

    The nanometer scale materials such as nanowires and nanotubes will be of particular interest as building blocks for designing novel sensors, catalysts, electronic, optical, and optoelectronic devices. However, in order to realize these applications, bulk amounts of nanowires and nanotubes need to be synthesized with precise control over the nanostructure characteristics. In addition, the structure-property relationships for one-dimensional structures are expected to be different than their bulk when their diameters are less than a characteristic Bohr exciton radius. This fundamental curiosity also necessitates bulk synthesis of nanostructures. The current bulk nanowire synthesis methods utilize either nanometer scale porous molds or nanometer scale transition metal clusters to template one-dimensional growth. All these techniques have inherent limitations in terms of control over the nanowire diameter distribution, composition, the growth direction, and the ability to generate abrupt interfaces within individual nanowires. In this dissertation, a new concept for bulk nucleation and growth of one-dimensional nanostructures is proposed and demonstrated for a variety of inorganic material systems. In this technique, multiple nanowires nucleate and grow from pools of low-melting metal melts when exposed to an activated gas phase containing the necessary precursors. This concept, hereby termed Low Melting Metals and Activated Gas phase (LMAG) mediated method, is specifically demonstrated for the synthesis of, (a) silicon nanowires grown using molten gallium and silane precursors; (b) silicon compound nanowires using solution of molten gallium and appropriate gas phase precursors, and (c) metal-oxide nanostructures grown using direct reaction of the respective metal melts and oxygen precursors. Nanowires resulted from the same molten gallium pool at high densities (>1011/cm2) and with narrow diameter distribution. The silicon nanowires synthesized using the LMAG

  6. Stable and high-speed SiC bulk growth without dendrites by the HTCVD method

    NASA Astrophysics Data System (ADS)

    Tokuda, Yuichiro; Makino, Emi; Sugiyama, Naohiro; Kamata, Isaho; Hoshino, Norihiro; Kojima, Jun; Hara, Kazukuni; Tsuchida, Hidekazu

    2016-08-01

    We investigate growth conditions to obtain high-quality SiC bulk crystals by the High-Temperature Chemical Vapor Deposition (HTCVD) method. Formation of dendrite crystals, which sometimes occurs on the growth front and degrades the material quality, is raised as an issue. We find that a bulk crystal growth under a high vertical temperature gradient, where the temperature of the back side of the bulk crystal is much lower than that of the crystal surface, suppresses the formation of dendrite crystals. Under growth conditions with a high temperature gradient, a very high-speed growth of 2.4 mm/h is achieved without the formation of dendrite crystals. Growth of a thick 4H-SiC bulk crystal without the dendrites is demonstrated and the quality of a grown crystal is evaluated.

  7. Bulk Moisture and Salinity Sensor

    NASA Technical Reports Server (NTRS)

    Nurge, Mark; Monje, Oscar; Prenger, Jessica; Catechis, John

    2013-01-01

    Measurement and feedback control of nutrient solutions in plant root zones is critical to the development of healthy plants in both terrestrial and reduced-gravity environments. In addition to the water content, the amount of fertilizer in the nutrient solution is important to plant health. This typically requires a separate set of sensors to accomplish. A combination bulk moisture and salinity sensor has been designed, built, and tested with different nutrient solutions in several substrates. The substrates include glass beads, a clay-like substrate, and a nutrient-enriched substrate with the presence of plant roots. By measuring two key parameters, the sensor is able to monitor both the volumetric water content and salinity of the nutrient solution in bulk media. Many commercially available moisture sensors are point sensors, making localized measurements over a small volume at the point of insertion. Consequently, they are more prone to suffer from interferences with air bubbles, contact area of media, and root growth. This makes it difficult to get an accurate representation of true moisture content and distribution in the bulk media. Additionally, a network of point sensors is required, increasing the cabling, data acquisition, and calibration requirements. measure the dielectric properties of a material in the annular space of the vessel. Because the pore water in the media often has high salinity, a method to measure the media moisture content and salinity simultaneously was devised. Characterization of the frequency response for capacitance and conductance across the electrodes was completed for 2-mm glass bead media, 1- to 2-mm Turface (a clay like media), and 1- to 2-mm fertilized Turface with the presence of root mass. These measurements were then used to find empirical relationships among capacitance (C), the dissipation factor (D), the volumetric water content, and the pore water salinity.

  8. MT6415CA: a 640×512-15µm CTIA ROIC for SWIR InGaAs detector arrays

    NASA Astrophysics Data System (ADS)

    Eminoglu, Selim; Isikhan, Murat; Bayhan, Nusret; Gulden, M. Ali; Incedere, O. Samet; Soyer, S. Tuncer; Kocak, Serhat; Yilmaz, Gokhan S.; Akin, Tayfun

    2013-06-01

    This paper reports the development of a new low-noise CTIA ROIC (MT6415CA) suitable for SWIR InGaAs detector arrays for low-light imaging applications. MT6415CA is the second product in the MT6400 series ROICs from Mikro-Tasarim Ltd., which is a fabless IC design house specialized in the development of monolithic imaging sensors and ROICs for hybrid imaging sensors. MT6415CA is a low-noise snapshot CTIA ROIC, has a format of 640 × 512 and pixel pitch of 15 µm, and has been developed with the system-on-chip architecture in mind, where all the timing and biasing for this ROIC are generated on-chip without requiring any external inputs. MT6415CA is a highly configurable ROIC, where many of its features can be programmed through a 3-wire serial interface allowing on-the-fly configuration of many ROIC features. It performs snapshot operation both using Integrate-Then-Read (ITR) and Integrate-While-Read (IWR) modes. The CTIA type pixel input circuitry has three gain modes with programmable full-well-capacity (FWC) values of 10.000 e-, 20.000 e-, and 350.000 e- in the very high gain (VHG), high-gain (HG), and low-gain (LG) modes, respectively. MT6415CA has an input referred noise level of less than 5 e- in the very high gain (VHG) mode, suitable for very low-noise SWIR imaging applications. MT6415CA has 8 analog video outputs that can be programmed in 8, 4, or 2-output modes with a selectable analog reference for pseudo-differential operation. The ROIC runs at 10 MHz and supports frame rate values up to 200 fps in the 8-output mode. The integration time can be programmed up to 1s in steps of 0.1 µs. The ROIC uses 3.3 V and 1.8V supply voltages and dissipates less than 150 mW in the 4-output mode. MT6415CA is fabricated using a modern mixed-signal CMOS process on 200 mm CMOS wafers, and tested parts are available at wafer or die levels with test reports and wafer maps. A compact USB 3.0 camera and imaging software have been developed to demonstrate the imaging

  9. Growth of high quality bulk size single crystals of inverted solubility lithium sulphate monohydrate

    NASA Astrophysics Data System (ADS)

    Silambarasan, A.; Rajesh, P.; Ramasamy, P.

    2015-06-01

    The paper summarizes the processes of growing large lithium sulfate monohydrate (LSMH) single crystals. We have established a procedure to grow high quality bulk size single crystals of inverted solubility LSMH by a newly developed unidirectional crystallization technique called the Sankeranarayenan - Ramasamy (SR) method. The convective flow of crystal growth processes from solution and the conditions of growing crystals of various aspects were discussed. Good quality LSMH single crystal is grown of the size 20 mmX80 mm without cracks, localized-defects and inclusions. The as-grown crystals are suitable for piezoelectric and nonlinear optical applications.

  10. Growth of Bulk Single Crystals of Dicyanovinyl-Ansiole and its Derivatives for Nonlinear Optical Applications

    NASA Technical Reports Server (NTRS)

    Gebre, T.; Choi, J.; Wang, W. S.; Metzl, R.; Aggarwal, M. D.; Romero, Melvin; Clark, Ronald D.; Penn, Benjamin G.; Frazier, Donald O.

    1998-01-01

    Bulk single crystals of a series of thermally stable nonlinear optical organic materials, Dicyanovinyl-anisole (DIVA) and their methoxy derivatives, have been successfully grown using the Bridgman-Stockbarger technique. The growth conditions are chosen to be temperature gradient of 5 to 10 C/cm and lowering rate of 0.1 to 0.3 mm/h. Single crystals of DIVA and its derivatives, of 8 x 8 x 50 cu mm in size, have been grown while maintaining a flat solid-liquid growth interface.

  11. Growth of high quality bulk size single crystals of inverted solubility lithium sulphate monohydrate

    SciTech Connect

    Silambarasan, A.; Rajesh, P. Ramasamy, P.

    2015-06-24

    The paper summarizes the processes of growing large lithium sulfate monohydrate (LSMH) single crystals. We have established a procedure to grow high quality bulk size single crystals of inverted solubility LSMH by a newly developed unidirectional crystallization technique called the Sankeranarayenan - Ramasamy (SR) method. The convective flow of crystal growth processes from solution and the conditions of growing crystals of various aspects were discussed. Good quality LSMH single crystal is grown of the size 20 mmX80 mm without cracks, localized-defects and inclusions. The as-grown crystals are suitable for piezoelectric and nonlinear optical applications.

  12. Flexoelectricity as a bulk property

    NASA Astrophysics Data System (ADS)

    Resta, Raffaele

    2010-03-01

    Piezoelectric composites can be created using nonpiezoelectric materials, by exploiting flexoelectricity. This is by definition the linear response of polarization to strain gradient, and is symmetry-allowed even in elemental crystals. However, the basic issue whether flexoelectricity is a bulk or a surface material property is open. We mention that the analogous issue about piezoelectricity is nontrivial either.^1 In this first attempt towards a full theory of flexoelectricity we prove that, for a simple class of strain and strain gradients, flexoelectricity is indeed a bulk effect. The key ingredients of the present theory are the long-range perturbations linearly induced by a unit displacement of a single nucleus in an otherwise perfect crystal: to leading order these are dipolar, quadrupolar, and octupolar. The corresponding tensors have rank 2, 3, and 4, respectively. Whereas dipoles and quadrupoles provide the piezoelectric response,^1 we show that dipoles and octupoles provide the flexoelectric response in nonpiezoelectric crystals. We conjecture that the full dipole and octupole tensors provide the flexoelectric response to the most general form of strain gradient. Our problem has a close relationship to the one of the ``absolute'' deformation potentials, which is based on a similar kind of dipolar and octupolar tensors.^2 ^1 R. M. Martin, Phys. Rev. B 5, 1607 (1972). ^2 R. Resta, L. Colombo and S. Baroni, Phys. Rev. B 41, 12538 (1990).

  13. 49 CFR 172.514 - Bulk packagings.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Bulk packagings. 172.514 Section 172.514... SECURITY PLANS Placarding § 172.514 Bulk packagings. (a) Except as provided in paragraph (c) of this section, each person who offers for transportation a bulk packaging which contains a hazardous...

  14. 49 CFR 172.514 - Bulk packagings.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Bulk packagings. 172.514 Section 172.514... SECURITY PLANS Placarding § 172.514 Bulk packagings. (a) Except as provided in paragraph (c) of this section, each person who offers for transportation a bulk packaging which contains a hazardous...

  15. 49 CFR 172.514 - Bulk packagings.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Bulk packagings. 172.514 Section 172.514... SECURITY PLANS Placarding § 172.514 Bulk packagings. (a) Except as provided in paragraph (c) of this section, each person who offers for transportation a bulk packaging which contains a hazardous...

  16. 49 CFR 172.514 - Bulk packagings.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Bulk packagings. 172.514 Section 172.514... SECURITY PLANS Placarding § 172.514 Bulk packagings. (a) Except as provided in paragraph (c) of this section, each person who offers for transportation a bulk packaging which contains a hazardous...

  17. 49 CFR 172.514 - Bulk packagings.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Bulk packagings. 172.514 Section 172.514... SECURITY PLANS Placarding § 172.514 Bulk packagings. (a) Except as provided in paragraph (c) of this section, each person who offers for transportation a bulk packaging which contains a hazardous...

  18. Introduction to the Growth of Bulk Single Crystals of Two-Dimensional Transition-Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Ueno, Keiji

    2015-12-01

    Semiconducting two-dimensional transition-metal dichalcogenides (MX2) are attracting much attention as promising materials for a new generation of optical and electronic devices. MX2 compounds are complementary or competitive to graphene because of the existence of a native band gap. The growth of large and high-quality bulk single crystals is one of the critical issues for the application of MX2 compounds, whose bulk crystals are generally grown by the chemical vapor transport (CVT) method. In the present review, I introduce experimental techniques required for the CVT growth of high-quality MX2 single crystals.

  19. Prediction of the Viscoelastic Bulk Modulus

    NASA Astrophysics Data System (ADS)

    Guo, Jiaxi; Simon, Sindee

    2010-03-01

    The bulk and shear viscoelastic responses for several materials appear to arise from the same molecular mechanisms at short times, i.e., Andrade creep where the KWW beta parameter is approximately 0.3. If this is indeed the case, prediction and placement of the bulk viscoelastic response can be made simply by knowing the limiting elastic and rubbery bulk moduli and the viscoelastic shear response. The proposed methodology, which uses only easily measured functions, is considerably less time- and labor-intensive than direct measurement of the viscoelastic bulk modulus. Here we investigate this hypothesis and compare the calculated viscoelastic bulk responses for several materials to existing data in the literature.

  20. Performance of near-infrared InGaAs focal plane array with different series resistances to p-InP layer

    NASA Astrophysics Data System (ADS)

    Shao, Xiumei; Li, Xue; Li, Tao; Huang, Zhangcheng; Chen, Yu; Tang, Hengjing; Gong, Haimei

    2014-05-01

    A planar-type InGaAs linear detector was designed and fabricated based on n-i-n+ type InP/In0.53Ga0.47As/InP epitaxial materials. The major process of the detector contains planar diffusion, surface passivation, metal contact and annealing. The I-V curves and the relative spectral response were measured at room temperature. The relative spectral response is in the range of 0.9 μm to 1.68 μm. The R0A of the detector is about 2×106 Ω•cm2 and the dark current density is 5~10nA/cm2 at -10mV bias voltage. The linear detectors were wire-bonded with readout integrated circuits (ROIC) to form focal plane array (FPA). The input stage of the ROIC is based on capacitive-feedback transimpedance amplifier (CTIA) with a capacitor (Cint) to be 0.1pF. However, the FPA signals are oscillating especially when close to the saturation. The ohmic contact on p-InP region plays an important role in the performance of detectors and FPAs. In this case, the series resistance to p-InP layer of each pixel is up to 1×106Ω. The FPAs were simulated in case of InGaAs detectors with different series resistances. According to the simulation results, the bandwidth of CTIA is lowering along with Rs increasing, and the signals of the FPAs oscillate when the series resistances are beyond 4×104Ω. The reason for the unstable oscillation of FPA is due to the series resistance of the detector which is too high enough. Then, the annealing process of the detectors was improved and the series resistances were lower than 1×104Ω. The optimized InGaAs linear detectors were wire-bonded with the same ROIC. The oscillation of the signals disappears and the FPA shows good stability.

  1. A low-noise 15-μm pixel-pitch 640×512 hybrid InGaAs image sensor for night vision

    NASA Astrophysics Data System (ADS)

    Guellec, Fabrice; Dubois, Sébastien; de Borniol, Eric; Castelein, Pierre; Martin, Sébastien; Guiguet, Romain; Tchagaspanian, Micha"l.; Rouvié, Anne; Bois, Philippe

    2012-03-01

    Hybrid InGaAs focal plane arrays are very interesting for night vision because they can benefit from the nightglow emission in the Short Wave Infrared band. Through a collaboration between III-V Lab and CEA-Léti, a 640x512 InGaAs image sensor with 15μm pixel pitch has been developed. The good crystalline quality of the InGaAs detectors opens the door to low dark current (around 20nA/cm2 at room temperature and -0.1V bias) as required for low light level imaging. In addition, the InP substrate can be removed to extend the detection range towards the visible spectrum. A custom readout IC (ROIC) has been designed in a standard CMOS 0.18μm technology. The pixel circuit is based on a capacitive transimpedance amplifier (CTIA) with two selectable charge-to-voltage conversion gains. Relying on a thorough noise analysis, this input stage has been optimized to deliver low-noise performance in high-gain mode with a reasonable concession on dynamic range. The exposure time can be maximized up to the frame period thanks to a rolling shutter approach. The frame rate can be up to 120fps or 60fps if the Correlated Double Sampling (CDS) capability of the circuit is enabled. The first results show that the CDS is effective at removing the very low frequency noise present on the reference voltage in our test setup. In this way, the measured total dark noise is around 90 electrons in high-gain mode for 8.3ms exposure time. It is mainly dominated by the dark shot noise for a detector temperature settling around 30°C when not cooled. The readout noise measured with shorter exposure time is around 30 electrons for a dynamic range of 71dB in high-gain mode and 108 electrons for 79dB in low-gain mode.

  2. Processing of bulk metallic glass.

    PubMed

    Schroers, Jan

    2010-04-12

    Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, particularly where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers has uncovered novel thermoplastic forming (TPF)-based processing opportunities. Unique among metal processing methods, TPF utilizes the dramatic softening exhibited by a BMG as it approaches its glass-transition temperature and decouples the rapid cooling required to form a glass from the forming step. This article reviews crystallization processes in BMG former and summarizes and compares TPF-based processing methods. Finally, an assessment of scientific and technological advancements required for broader commercial utilization of BMGs will be made. PMID:20496386

  3. Gold based bulk metallic glass

    SciTech Connect

    Schroers, Jan; Lohwongwatana, Boonrat; Johnson, William L.; Peker, Atakan

    2005-08-08

    Gold-based bulk metallic glass alloys based on Au-Cu-Si are introduced. The alloys exhibit a gold content comparable to 18-karat gold. They show very low liquidus temperature, large supercooled liquid region, and good processibility. The maximum casting thickness exceeds 5 mm in the best glassformer. Au{sub 49}Ag{sub 5.5}Pd{sub 2.3}Cu{sub 26.9}Si{sub 16.3} has a liquidus temperature of 644 K, a glass transition temperature of 401 K, and a supercooled liquid region of 58 K. The Vickers hardness of the alloys in this system is {approx}350 Hv, twice that of conventional 18-karat crystalline gold alloys. This combination of properties makes the alloys attractive for many applications including electronic, medical, dental, surface coating, and jewelry.

  4. Gold based bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Lohwongwatana, Boonrat; Johnson, William L.; Peker, Atakan

    2005-08-01

    Gold-based bulk metallic glass alloys based on Au-Cu-Si are introduced. The alloys exhibit a gold content comparable to 18-karat gold. They show very low liquidus temperature, large supercooled liquid region, and good processibility. The maximum casting thickness exceeds 5mm in the best glassformer. Au49Ag5.5Pd2.3Cu26.9Si16.3 has a liquidus temperature of 644K, a glass transition temperature of 401K, and a supercooled liquid region of 58K. The Vickers hardness of the alloys in this system is ˜350Hv, twice that of conventional 18-karat crystalline gold alloys. This combination of properties makes the alloys attractive for many applications including electronic, medical, dental, surface coating, and jewelry.

  5. Isotopic signatures by bulk analyses

    SciTech Connect

    Efurd, D.W.; Rokop, D.J.

    1997-12-01

    Los Alamos National Laboratory has developed a series of measurement techniques for identification of nuclear signatures by analyzing bulk samples. Two specific applications for isotopic fingerprinting to identify the origin of anthropogenic radioactivity in bulk samples are presented. The first example is the analyses of environmental samples collected in the US Arctic to determine the impact of dumping of radionuclides in this polar region. Analyses of sediment and biota samples indicate that for the areas sampled the anthropogenic radionuclide content of sediments was predominantly the result of the deposition of global fallout. The anthropogenic radionuclide concentrations in fish, birds and mammals were very low. It can be surmised that marine food chains are presently not significantly affected. The second example is isotopic fingerprinting of water and sediment samples from the Rocky Flats Facility (RFP). The largest source of anthropogenic radioactivity presently affecting surface-waters at RFP is the sediments that are currently residing in the holding ponds. One gram of sediment from a holding pond contains approximately 50 times more plutonium than 1 liter of water from the pond. Essentially 100% of the uranium in Ponds A-1 and A-2 originated as depleted uranium. The largest source of radioactivity in the terminal Ponds A-4, B-5 and C-2 was naturally occurring uranium and its decay product radium. The uranium concentrations in the waters collected from the terminal ponds contained 0.05% or less of the interim standard calculated derived concentration guide for uranium in waters available to the public. All of the radioactivity observed in soil, sediment and water samples collected at RFP was naturally occurring, the result of processes at RFP or the result of global fallout. No extraneous anthropogenic alpha, beta or gamma activities were detected. The plutonium concentrations in Pond C-2 appear to vary seasonally.

  6. Structural and optical properties of (In,Ga)As/GaP quantum dots and (GaAsPN/GaPN) diluted-nitride nanolayers coherently grown onto GaP and Si substrates for photonics and photovoltaics applications

    NASA Astrophysics Data System (ADS)

    Durand, O.; Robert, C.; Nguyen Thanh, T.; Almosni, S.; Quinci, T.; Kuyyalil, J.; Cornet, C.; Létoublon, A.; Levallois, C.; Jancu, J.-M.; Even, J.; Pédesseau, L.; Perrin, M.; Bertru, N.; Sakri, A.; Boudet, N.; Ponchet, A.; Rale, P.; Lombez, L.; Guillemoles, J.-F.; Marie, X.; Balocchi, A.; Turban, P.; Tricot, S.; Modreanu, Mircea; Loualiche, S.; Le Corre, A.

    2013-01-01

    Lattice-matched GaP-based nanostructures grown on silicon substrates is a highly rewarded route for coherent integration of photonics and high-efficiency photovoltaic devices onto silicon substrates. We report on the structural and optical properties of selected MBE-grown nanostructures on both GaP substrates and GaP/Si pseudo-substrates. As a first stumbling block, the GaP/Si interface growth has been optimised thanks to a complementary set of thorough structural analyses. Photoluminescence and time-resolved photoluminescence studies of self-assembled (In,Ga)As quantum dots grown on GaP substrate demonstrate a proximity of two different types of optical transitions interpreted as a competition between conduction band states in X and Γ valleys. Structural properties and optical studies of GaAsP(N)/GaP(N) quantum wells coherently grown on GaP substrates and GaP/Si pseudo substrates are reported. Our results are found to be suitable for light emission applications in the datacom segment. Then, possible routes are drawn for larger wavelengths applications, in order to address the chip-to-chip and within-a-chip optical interconnects and the optical telecom segments. Finally, results on GaAsPN/GaP heterostructures and diodes, suitable for PV applications are reported.

  7. Spontaneous atomic ordering in MOVPE grown gallium arsenide antimonide

    NASA Astrophysics Data System (ADS)

    Jiang, Weiyang

    Spontaneous atomic ordering of semiconductor alloys is of great practical and fundamental interest. Atomic ordering of III-V alloys such as InGaP has been extensively studied experimentally and theoretically. In this thesis, we investigate a little-studied, atomic-ordering phenomenon, the so-called CuAu structure in the III-V material GaAsSb, grown by the technique of metalorganic vapor-phase epitaxy (MOVPE). Despite being first observed in 1986 in this material, there is as yet no detailed microscopic model for its formation mechanism. A key part of the thesis involves the study of surfactant effects on the ordering process in GaAsSb. Surfactants are elements which modify the growth surface without incorporation in the bulk. Nevertheless, they influence the incorporation of the bulk elements. We first explored the surfactant behavior of Bi on GaAs in order to understand how Bi incorporates at the surface and in the bulk in a related III-V material. For GaAs (001), Bi surface layers are stable at temperatures below 500°C but rapidly desorb at temperatures of 550°C and higher. Bi coverages of over 1 ML induce the formation of Bi islands, whose sizes increase with increasing Bi exposure. Bulk incorporation of Bi remains essentially zero at typical MOVPE growth temperatures. In the case of GaAsSb alloys, Bi surfactant was found to induce CuAu ordering, with no measurable Bi incorporation in the bulk. High resolution TEM was used to study the detailed microstructural features for ordered and disordered samples. The domain sizes of the ordered regions are from 5 nm to 20 nm under all growth conditions. In contrast to orderings in other alloys such as InGaP, CuAu ordering had no observable effect on the bandgap. CuAu ordering in GaAsSb was studied in a function of growth conditions, including Bi surfactant concentration, growth temperature, growth rate, and substrate miscut. All of these experiments confirm that bulk CuAu ordering is a surface driven, rather than bulk

  8. Characteristics of the dynamics of breakdown filaments in Al{sub 2}O{sub 3}/InGaAs stacks

    SciTech Connect

    Palumbo, F.; Shekhter, P.; Eizenberg, M.; Cohen Weinfeld, K.

    2015-09-21

    In this paper, the Al{sub 2}O{sub 3}/InGaAs interface was studied by X-ray photoelectron spectroscopy (XPS) after a breakdown (BD) event at positive bias applied to the gate contact. The dynamics of the BD event were studied by comparable XPS measurements with different current compliance levels during the BD event. The overall results show that indium atoms from the substrate move towards the oxide by an electro-migration process and oxidize upon arrival following a power law dependence on the current compliance of the BD event. Such a result reveals the physical feature of the breakdown characteristics of III-V based metal-oxide-semiconductor devices.

  9. Development of a large area InGaAs APD receiver based on an impact ionization engineered detector for free-space lasercomm applications

    NASA Astrophysics Data System (ADS)

    Burris, H. R.; Ferraro, M. S.; Freeman, W. T.; Moore, C. I.; Murphy, J. L.; Rabinovich, W. S.; Smith, W. R.; Summers, L. L.; Thomas, L. M.; Vilcheck, M. J.; Clark, W. R.; Waters, W. D.

    2012-06-01

    The U.S. Naval Research Laboratory (NRL) is developing a small size, weight and power (SWaP) free space lasercomm terminal for small unmanned airborne platforms. The terminal is based on a small gimbal developed by CloudCap Technology. A receiver with a large field of view and with sensitivity sufficient to meet the program range goals is required for this terminal. An InGaAs Avalanche Photodiode (APD) with internal structures engineered to reduce excess noise and keff in high gain applications was selected as the detector. The detector is a 350 micron diameter impact ionization engineered (I2E) APD developed by Optogration, Inc. Results of development and characterization of the receiver will be presented.

  10. Fermi level pinning in metal/Al{sub 2}O{sub 3}/InGaAs gate stack after post metallization annealing

    SciTech Connect

    Winter, R.; Krylov, I.; Cytermann, C.; Eizenberg, M.; Tang, K.; Ahn, J.; McIntyre, P. C.

    2015-08-07

    The effect of post metal deposition annealing on the effective work function in metal/Al{sub 2}O{sub 3}/InGaAs gate stacks was investigated. The effective work functions of different metal gates (Al, Au, and Pt) were measured. Flat band voltage shifts for these and other metals studied suggest that their Fermi levels become pinned after the post-metallization vacuum annealing. Moreover, there is a difference between the measured effective work functions of Al and Pt, and the reported vacuum work function of these metals after annealing. We propose that this phenomenon is caused by charging of indium and gallium induced traps at the annealed metal/Al{sub 2}O{sub 3} interface.

  11. A 20MHz 15μm pitch 128×128 CTIA ROIC for InGaAs focal plane array

    NASA Astrophysics Data System (ADS)

    Huang, Zhangcheng; Chen, Yu; Huang, Songlei; Fang, Jiaxiong

    2014-11-01

    A 128×128 matrix readout integrated circuit (ROIC) for 15×15 μm2 InGaAs focal plane array (FPA) is reported in this paper. Capacitive-feedback Trans-Impedance Amplifier (CTIA) and correlated double sampling (CDS) are both involved in ROIC pixel which dissipates 90nW and has a full-well-capacity (FWC) of about 78,000 e-. Noises of ROIC pixel are analyzed and distribution method of capacitors in pixel is discussed in order to obtain low-noise performance. In column buffer circuit, a new pre-charging technique is developed to realize readout rate of 20 MHz with low power consumption. The ROIC is fabricated with 0.18-μm 3.3 V mixed signal CMOS process. Test results show that the ROIC has an equivalent input noise of about 181e- and can achieve a readout rate of 20 MHz.

  12. Interface trap density and mobility extraction in InGaAs buried quantum well metal-oxide-semiconductor field-effect-transistors by gated Hall method

    SciTech Connect

    Chidambaram, Thenappan; Madisetti, Shailesh; Greene, Andrew; Yakimov, Michael; Tokranov, Vadim; Oktyabrsky, Serge; Veksler, Dmitry; Hill, Richard

    2014-03-31

    In this work, we are using a gated Hall method for measurement of free carrier density and electron mobility in buried InGaAs quantum well metal-oxide-semiconductor field-effect-transistor channels. At room temperature, mobility over 8000 cm{sup 2}/Vs is observed at ∼1.4 × 10{sup 12} cm{sup −2}. Temperature dependence of the electron mobility gives the evidence that remote Coulomb scattering dominates at electron density <2 × 10{sup 11} cm{sup −2}. Spectrum of the interface/border traps is quantified from comparison of Hall data with capacitance-voltage measurements or electrostatic modeling. Above the threshold voltage, gate control is strongly limited by fast traps that cannot be distinguished from free channel carriers just by capacitance-based methods and can be the reason for significant overestimation of channel density and underestimation of carrier mobility from transistor measurements.

  13. Real-time continuous-wave terahertz line scanner based on a compact 1 × 240 InGaAs Schottky barrier diode array detector.

    PubMed

    Han, Sang-Pil; Ko, Hyunsung; Kim, Namje; Lee, Won-Hui; Moon, Kiwon; Lee, Il-Min; Lee, Eui Su; Lee, Dong Hun; Lee, Wangjoo; Han, Seong-Tae; Choi, Sung-Wook; Park, Kyung Hyun

    2014-11-17

    We demonstrate real-time continuous-wave terahertz (THz) line-scanned imaging based on a 1 × 240 InGaAs Schottky barrier diode (SBD) array detector with a scan velocity of 25 cm/s, a scan line length of 12 cm, and a pixel size of 0.5 × 0.5 mm². Foreign substances, such as a paper clip with a spatial resolution of approximately 1 mm that is hidden under a cracker, are clearly detected by this THz line-scanning system. The system consists of the SBD array detector, a 200-GHz gyrotron source, a conveyor system, and several optical components such as a high-density polyethylene cylindrical lens, metal cylindrical mirror, and THz wire-grid polarizer. Using the THz polarizer, the signal-to-noise ratio of the SBD array detector improves because the quality of the source beam is enhanced. PMID:25402136

  14. Strain-driven alignment of In nanocrystals on InGaAs quantum dot arrays and coupled plasmon-quantum dot emission

    SciTech Connect

    Urbanczyk, A.; Hamhuis, G. J.; Noetzel, R.

    2010-03-15

    We report the alignment of In nanocrystals on top of linear InGaAs quantum dot (QD) arrays formed by self-organized anisotropic strain engineering on GaAs (100) by molecular beam epitaxy. The alignment is independent of a thin GaAs cap layer on the QDs revealing its origin is due to local strain recognition. This enables nanometer-scale precise lateral and vertical site registration between the QDs and the In nanocrystals and arrays in a single self-organizing formation process. The plasmon resonance of the In nanocrystals overlaps with the high-energy side of the QD emission leading to clear modification of the QD emission spectrum.

  15. Curvature and bow of bulk GaN substrates

    NASA Astrophysics Data System (ADS)

    Foronda, Humberto M.; Romanov, Alexey E.; Young, Erin C.; Roberston, Christian A.; Beltz, Glenn E.; Speck, James S.

    2016-07-01

    We investigate the bow of free standing (0001) oriented hydride vapor phase epitaxy grown GaN substrates and demonstrate that their curvature is consistent with a compressive to tensile stress gradient (bottom to top) present in the substrates. The origin of the stress gradient and the curvature is attributed to the correlated inclination of edge threading dislocation (TD) lines away from the [0001] direction. A model is proposed and a relation is derived for bulk GaN substrate curvature dependence on the inclination angle and the density of TDs. The model is used to analyze the curvature for commercially available GaN substrates as determined by high resolution x-ray diffraction. The results show a close correlation between the experimentally determined parameters and those predicted from theoretical model.

  16. Iron bulk lasers working under cryogenic and room temperature

    NASA Astrophysics Data System (ADS)

    Jelínková, H.; Doroshenko, M. E.; Šulc, J.; Jelínek, M.; Nemec, M.; Zagoruiko, Y. A.; Kovalenko, N. O.; Gerasimenko, A. S.; Puzikov, V. M.; Komar, V. K.

    2014-12-01

    Temperature dependence of spectroscopic characteristics as well as laser properties of the bulk Bridgman-grown Fe:ZnSe and Fe,Cr:Zn1-xMgxSe (x = 0.19, 0.38) active media were investigated under room and various cryogenic - liquid nitrogen - temperature . The pumping was provided by Er:YAG laser radiation at the wavelength of 2.94 μm, with energy 15 mJ in 110 ns Q-switched pulse or 200 mJ in 220 μs free-running pulse. The 55 mm long hemispherical resonator was formed by a dichroic pumping mirror (T = 92 % @ 2.94 μm and R = 100% @ 4.5 μm) and a concave output coupler (R = 95 % @ 4.5 μm, r = 200 mm). A strong dependence of generated output radiation parameters on temperature was observed for all samples.

  17. Comparison of the degradation characteristics of AlON/InGaAs and Al{sub 2}O{sub 3}/InGaAs stacks

    SciTech Connect

    Palumbo, F. Krylov, I.; Eizenberg, M.

    2015-03-14

    In this paper, the degradation characteristics of MOS (Metal-Oxide-Semiconductor) stacks with Al{sub 2}O{sub 3}/AlON or Al{sub 2}O{sub 3} only as dielectric layers on InGaAs were studied. The dielectric nitrides are proposed as possible passivation layers to prevent InGaAs oxidation. At negative bias, it has been found out that the main contribution to the overall degradation of the gate oxide is dominated by the generation of positive charge in the gate oxide. This effect is pronounced in MOS stacks with Al{sub 2}O{sub 3}/AlON as dielectric, where we think the positive charge is mainly generated in the AlON interlayer. At positive bias, the degradation is dominated by buildup of negative charge due to electron trapping in pre-existing or stress-induced traps. For stress biases where the leakage currents are low, the changes in the electrical characteristics are dominated by electron-trapping into traps located in energy levels in the upper part of the semiconductor gap. For stress biases with higher leakage current levels, the electron trapping occurs in stress-induced traps increasing the shift of V{sub FB} towards positive bias. The overall results clearly show that the improvement of the high-k dielectric/InGaAs interface by introducing N into the Al-oxide does not necessarily mean an increase in the reliability of the MOS stack.

  18. Ammonothermal bulk GaN substrates for LEDs

    NASA Astrophysics Data System (ADS)

    Jiang, W.; Ehrentraut, D.; Kamber, D. S.; Downey, B. C.; Cook, J.; Grundmann, M.; Pakalapati, R. T.; Yoo, H.; D'Evelyn, M. P.

    2014-02-01

    Soraa has developed a novel ammonothermal approach for growth of high quality, true bulk GaN crystals at a greatly reduced cost. Soraa's patented approach, known as SCoRA (Scalable Compact Rapid Ammonothermal) utilizes internal heating to circumvent the material-property limitations of conventional ammonothermal reactors. The SCoRA reactor has capability for temperatures and pressures greater than 650 °C and 500 MPa, respectively, enabling higher growth rates than conventional ammonothermal techniques, yet is less expensive and more scalable than conventional autoclaves fabricated from nickel-based superalloys. SCoRA GaN growth has been performed on c-plane and m-plane seed crystals with diameters between 5 mm and 2" to thicknesses of 0.5-4 mm. The highest growth rates are greater than 40 μm/h and rates in the 10-30 μm/h range are routinely observed. These values are significantly larger than those achieved by conventional ammonothermal GaN growth and are sufficient for a cost-effective manufacturing process. Two-inch diameter, crack-free, free-standing, n-type bulk GaN crystals have been grown. The crystals have been characterized by a range of techniques, including x-ray diffraction rocking-curve (XRC) analysis, optical microscopy, cathodoluminescence (CL), optical spectroscopy, and capacitance-voltage measurements. The crystallinity of the grown crystals is very good, with FWHM values of 15-80 arc-sec and average dislocation densities below 5 x 105 cm-2.

  19. Aspects of silicon bulk lifetimes

    NASA Technical Reports Server (NTRS)

    Landsberg, P. T.

    1985-01-01

    The best lifetimes attained for bulk crytalline silicon as a function of doping concentrations are analyzed. It is assumed that the dopants which set the Fermi level do not contribute to the recombination traffic which is due to the unknown defect. This defect is assumed to have two charge states: neutral and negative, the neutral defect concentration is frozen-in at some temperature T sub f. The higher doping concentrations should include the band-band Auger effect by using a generalization of the Shockley-Read-Hall (SRH) mechanism. The generalization of the SRH mechanism is discussed. This formulation gives a straightforward procedure for incorporating both band-band and band-trap Auger effects in the SRH procedure. Two related questions arise in this context: (1) it may sometimes be useful to write the steady-state occupation probability of the traps implied by SRH procedure in a form which approximates to the Fermi-Dirac distribution; and (2) the effect on the SRH mechanism of spreading N sub t levels at one energy uniformly over a range of energies is discussed.

  20. Covalent bulk functionalization of graphene.

    PubMed

    Englert, Jan M; Dotzer, Christoph; Yang, Guang; Schmid, Martin; Papp, Christian; Gottfried, J Michael; Steinrück, Hans-Peter; Spiecker, Erdmann; Hauke, Frank; Hirsch, Andreas

    2011-04-01

    Graphene, a truly two-dimensional and fully π-conjugated honeycomb carbon network, is currently evolving into the most promising successor to silicon in micro- and nanoelectronic applications. However, its wider application is impeded by the difficulties in opening a bandgap in its gapless band-structure, as well as the lack of processability in the resultant intrinscially insoluble material. Covalent chemical modification of the π-electron system is capable of addressing both of these issues through the introduction of variable chemical decoration. Although there has been significant research activity in the field of functionalized graphene, most work to date has focused on the use of graphene oxide. In this Article, we report on the first wet chemical bulk functionalization route beginning with pristine graphite that does not require initial oxidative damage of the graphene basal planes. Through effective reductive activation, covalent functionalization of the charged graphene is achieved by organic diazonium salts. Functionalization was observed spectroscopically, and successfully prevents reaggregation while providing solubility in common organic media. PMID:21430685

  1. Diffusion of oxygen in bulk GaN crystals at high temperature and at high pressure

    NASA Astrophysics Data System (ADS)

    Sadovyi, B.; Nikolenko, A.; Weyher, J. L.; Grzegory, I.; Dziecielewski, I.; Sarzynski, M.; Strelchuk, V.; Tsykaniuk, B.; Belyaev, O.; Petrusha, I.; Turkevich, V.; Kapustianyk, V.; Albrecht, M.; Porowski, S.

    2016-09-01

    Experimental studies of diffusion of oxygen in bulk wurtzite-type GaN crystals grown by Halide Vapor Phase Epitaxy (HVPE) are reported. Oxygen concentration profiles were studied in as-grown GaN crystals and also after annealing of crystals at temperatures up to 3400 K and pressures up to 9 GPa. Investigated crystals contained large conical defects i.e. pinholes of significantly higher oxygen concentration (NO=(2-4)×1019 cm-3) than that in the bulk matrix (NO<1×1017 cm-3). The pinholes were revealed by a photo-etching method in as-grown and annealed GaN samples. Confocal micro-Raman spectroscopy was applied to measure the profiles of free electron concentration, which directly corresponds to the concentration of oxygen impurity. Lateral scanning across the interfaces between pinholes and matrix in the as-grown HVPE GaN crystals showed sharp step-like carrier concentration profiles. Annealing at high temperature and high pressure resulted in the diffusion blurring of the profiles. Analysis of obtained data allowed for the first time for estimation of oxygen diffusion coefficients DO(T, P). The obtained values of DO(T, P) are anomalously small similarly to the values obtained by Harafuji et al. by molecular dynamic calculations for self-diffusion of nitrogen. Whereas oxygen and nitrogen are on the same sublattice it could explain the similarity of their diffusion coefficients.

  2. 1.3-μm edge- and surface-emitting quantum dot lasers grown on GaAs substrates

    NASA Astrophysics Data System (ADS)

    Ustinov, Victor M.; Zhukov, Alexey E.; Maleev, Nikolay A.; Egorov, Anton Y.; Kovsh, Alexey R.; Mikhrin, Sergei S.; Cherkashin, Nikolai A.; Shernyakov, Yuri M.; Maximov, Mikhail V.; Tsatsul'nikov, Anrei; Ledentsov, Nikolai N.; Alferov, Zhores I.; Lott, James A.; Bimberg, Dieter

    2002-06-01

    The development of 1.3 micron VCSELs is currently considered to give a strong impulse for a wide use of ultra-fast local area networks. In the present work we discuss MBE growth and characteristics of InAs/GaAs quantum dot (QD) lasers, we also give characteristics of 1.3 micron QD VCSELs grown on GaAs and compare them with those of 1.3 micron InGaAsN/GaAs QW VCSELs. Overgrowing the InAs quantum dot array with thin InGaAs layer allows us to achieve 1.3 micron emission. Long stripe lasers showed low threshold current density (<100 A/cm2), high differential efficiency (>50%), and low internal loss (1-2 cm-1). Maximum continuous wave (CW) output power for wide stripe lasers was as high as 2.7 W and 110 mW for single mode devices. Uncoated broad area lasers showed no visible degradation of characteristics during 450 hours (60C, ambient environment). 1.3 micron InGaAsN/GaAs QW VCSELs are characterized by higher optical loss and lower differential efficiency than QD VCSELs. Due to high gain in the active region QW VCSELS demonstrate high output power (1 mW). QW VCSELs show extremely low internal round-trip optical loss (<0.05%), low threshold currents (<2 mA), high differential efficiency (40%) and output power (600 microW).

  3. Bulk entanglement spectrum in gapped spin ladders

    NASA Astrophysics Data System (ADS)

    Santos, Raul A.; Jian, Chao-Ming; Lundgren, Rex

    2016-06-01

    We study the bulk entanglement of a series of gapped ground states of spin ladders, representative of the Haldane phase. These ground states of spin S /2 ladders generalize the valence bond solid ground state. In the case of spin 1/2 ladders, we study a generalization of the Affleck-Kennedy-Lieb-Tasaki and Nersesyan-Tsvelik states and fully characterize the bulk entanglement Hamiltonian. In the case of general spin S , we argue that in the Haldane phase the bulk entanglement spectrum of a half-integer ladder is either gapless or possess a degenerate ground state. For ladders with integer valued spin particles, the generic bulk entanglement spectrum should have an entanglement gap. Finally, we give an example of a series of trivial states of higher spin S >1 in which the bulk entanglement Hamiltonian is critical, signaling that the relation between topological states and a critical bulk entanglement Hamiltonian is not unique to topological systems.

  4. Relative entropy equals bulk relative entropy

    NASA Astrophysics Data System (ADS)

    Jafferis, Daniel L.; Lewkowycz, Aitor; Maldacena, Juan; Suh, S. Josephine

    2016-06-01

    We consider the gravity dual of the modular Hamiltonian associated to a general subregion of a boundary theory. We use it to argue that the relative entropy of nearby states is given by the relative entropy in the bulk, to leading order in the bulk gravitational coupling. We also argue that the boundary modular flow is dual to the bulk modular flow in the entanglement wedge, with implications for entanglement wedge reconstruction.

  5. Growth and characterization studies of sodium Di(L-Malato) borate bulk single crystal: A promising nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Senthil, A.; Loganayaki, M.; Lenin, M.; Ramasamy, P.

    2012-06-01

    A semi-organic nonlinear optical material, sodium di(L-malato) borate (NaDMB) has been synthesized. Optically good quality bulk single crystal of NaDMB was successfully grown by slow evaporation solution technique (SEST) and Sankaranarayanan-Ramasamy (SR) method at 36 °C. Transparent, colourless crystal of size 22 mm X 8 mm X 6 mm with well defined morphology was grown by SEST and <100> oriented unidirectional bulk single crystal of size 48 mm length and 16 mm diameter was grown by SR method. The grown crystals were subjected to single crystal X-ray diffraction studies. The crystal belongs to monoclinic structure with space group P21. The grown crystals were characterized by UV-vis studies. The structural perfection of the grown crystal has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The differential thermal (DTA) and thermogravimetric (TG) analysis traces reveal the thermal stability of the sample. The second-harmonic generation efficiency was estimated by Kurtz and Perry powder technique.

  6. Low Temperature Photoluminescence Characterization of Orbitally Grown CdZnTe

    NASA Technical Reports Server (NTRS)

    Ritter, Timothy M.; Larson, D. J.

    1998-01-01

    The II-VI ternary alloy CdZnTe is a technologically important material because of its use as a lattice matched substrate for HgCdTe based devices. The increasingly stringent requirements on performance that must be met by such large area infrared detectors also necessitates a higher quality substrate. Such substrate material is typically grown using the Bridgman technique. Due to the nature of bulk semiconductor growth, gravitationally dependent phenomena can adversely affect crystalline quality. The most direct way to alleviate this problem is by crystal growth in a reduced gravity environment. Since it requires hours, even days, to grow a high quality crystal, an orbiting space shuttle or space station provides a superb platform on which to conduct such research. For well over ten years NASA has been studying the effects of microgravity semiconductor crystal growth. This paper reports the results of photoluminescence characterization performed on an arbitrary grown CdZnTe bulk crystal.

  7. Harvesting microalgae grown on wastewater.

    PubMed

    Udom, Innocent; Zaribaf, Behnaz H; Halfhide, Trina; Gillie, Benjamin; Dalrymple, Omatoyo; Zhang, Qiong; Ergas, Sarina J

    2013-07-01

    The costs and life cycle impacts of microalgae harvesting for biofuel production were investigated. Algae were grown in semi-continuous culture in pilot-scale photobioreactors under natural light with anaerobic digester centrate as the feed source. Algae suspensions were collected and the optimal coagulant dosages for metal salts (alum, ferric chloride), cationic polymer (Zetag 8819), anionic polymer (E-38) and natural coagulants (Moringa Oleifera and Opuntia ficus-indica cactus) were determined using jar tests. The relative dewaterability of the algae cake was estimated by centrifugation. Alum, ferric chloride and cationic polymer could all achieve >91% algae recovery at optimal dosages. Life cycle assessment (LCA) and cost analysis results revealed that cationic polymer had the lowest cost but the highest environmental impacts, while ferric chloride had the highest cost and lowest environmental impacts. Based on the LCA results, belt presses are the recommended algae dewatering technology prior to oil extraction. PMID:23648758

  8. Enhanced performance of room-temperature-grown epitaxial thin films of vanadium dioxide

    SciTech Connect

    Nag, Joyeeta; Payzant, E Andrew; More, Karren Leslie; HaglundJr., Richard F

    2011-01-01

    Stoichiometric vanadium dioxide in bulk, thin film and nanostructured forms exhibits an insulator-to-metal transition (IMT) accompanied by a structural phase transformation, induced by temperature, light, electric fields, doping or strain. We have grown epitaxial films of vanadium dioxide on c-plane (0001) of sapphire using two different procedures involving (1) room temperature growth followed by annealing and (2) direct high temperature growth. Strain at the film-substrate interface due to growth at different temperatures leads to interesting differences in morphologies and phase transition characteristics. Comparison of the morphologies and switching characteristics of the two films shows that contrary to conventional wisdom, the room-temperature grown films have smoother, more continuous morphologies and better switching performance, consistent with the behavior of epitaxially grown semiconductors.

  9. Secondary ion mass spectrometry of vapor-liquid-solid grown, Au-catalyzed, Si wires.

    PubMed

    Putnam, Morgan C; Filler, Michael A; Kayes, Brendan M; Kelzenberg, Michael D; Guan, Yunbin; Lewis, Nathan S; Eiler, John M; Atwater, Harry A

    2008-10-01

    Knowledge of the catalyst concentration within vapor-liquid-solid (VLS) grown semiconductor wires is needed in order to assess potential limits to electrical and optical device performance imposed by the VLS growth mechanism. We report herein the use of secondary ion mass spectrometry to characterize the Au catalyst concentration within individual, VLS-grown, Si wires. For Si wires grown by chemical vapor deposition from SiCl 4 at 1000 degrees C, an upper limit on the bulk Au concentration was observed to be 1.7 x 10(16) atoms/cm(3), similar to the thermodynamic equilibrium concentration at the growth temperature. However, a higher concentration of Au was observed on the sidewalls of the wires. PMID:18767881

  10. Properties of AlN film grown on Si (111)

    NASA Astrophysics Data System (ADS)

    Dai, Yiquan; Li, Shuiming; Sun, Qian; Peng, Qing; Gui, Chengqun; Zhou, Yu; Liu, Sheng

    2016-02-01

    Stress and strain in an AlN film grown on Si (111) substrate have been evaluated by measuring Raman frequency shifts. Mechanical properties and phonon deformation potentials of AlN are evaluated by first principles calculations. The calculation model is verified by comparing the calculated Raman frequencies and frequencies detected from a bulk single crystal. Results show that the two sets of frequencies agree very well with each other. Thus, with the same verified model and parameters, elastic constants and phonon deformation potentials are calculated. Additionally, we successfully develop a numerical model to verify the calculation above and the model itself is also useful to predict properties of crystal films. Finally, the stress, strain, and piezoelectric properties are analyzed and compared for films on different substrates.

  11. Effects of continuously or step-continuously graded buffer on the performance of wavelength extended InGaAs photodetectors

    NASA Astrophysics Data System (ADS)

    Du, B.; Gu, Y.; Zhang, Y. G.; Chen, X. Y.; Xi, S. P.; Ma, Y. J.; Ji, W. Y.; Shi, Y. H.; Li, X.; Gong, H. M.

    2016-04-01

    High In content In0.83Ga0.17As photodetector structures with a new kind of buffer scheme have been grown on InP substrate by gas source molecular beam epitaxy. The effects of buffer scheme on material properties and device performances have been investigated both experimentally and theoretically. The structures with the combination of step and continuously graded buffers show reduced surface roughness, improved photoluminescence intensity and lower device dark current than those with simplex continuously graded buffer at the same buffer thickness. The mechanisms have been discussed from X-ray diffraction, photoluminescence, dark current measurements and model analysis.

  12. 27 CFR 20.191 - Bulk articles.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Bulk articles. 20.191... Users of Specially Denatured Spirits Operations by Users § 20.191 Bulk articles. Users who convey articles in containers exceeding one gallon may provide the recipient with a photocopy of subpart G of...

  13. 27 CFR 20.191 - Bulk articles.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Bulk articles. 20.191... Users of Specially Denatured Spirits Operations by Users § 20.191 Bulk articles. Users who convey articles in containers exceeding one gallon may provide the recipient with a photocopy of subpart G of...

  14. 27 CFR 20.191 - Bulk articles.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Bulk articles. 20.191... Users of Specially Denatured Spirits Operations by Users § 20.191 Bulk articles. Users who convey articles in containers exceeding one gallon may provide the recipient with a photocopy of subpart G of...

  15. Temporal soil bulk density following tillage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil is the medium for air, energy, water, and chemical transport between the atmosphere and the solid earth. Soil bulk density is a key variable impacting the rate at which this transport occurs. Typically, soil bulk density is measured by the gravimetric method, where a sample of known volume is t...

  16. 27 CFR 20.191 - Bulk articles.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bulk articles. 20.191... Users of Specially Denatured Spirits Operations by Users § 20.191 Bulk articles. Users who convey articles in containers exceeding one gallon may provide the recipient with a photocopy of subpart G of...

  17. 27 CFR 20.191 - Bulk articles.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Bulk articles. 20.191... Users of Specially Denatured Spirits Operations by Users § 20.191 Bulk articles. Users who convey articles in containers exceeding one gallon may provide the recipient with a photocopy of subpart G of...

  18. Effect of solvents on the bulk growth of 4-aminobenzophenone single crystals: a potential material for blue and green lasers.

    PubMed

    Natarajan, V; Usharani, S; Arivanandhan, M; Anandan, P; Hayakawa, Y

    2015-06-15

    Although 4-aminobenzophenone (4-ABP) is the best derivative of benzophenone with 260 times higher second harmonic generation (SHG) efficiency than potassium dihydrogen phosphate (KDP), growth of high quality bulk crystal still remains a difficult task. In the present work, the effect of solvents on solubility and growth aspects of 4-ABP was investigated to grow inclusion free 4-ABP crystals. The growth processes were discussed based on solute-solvent interaction in two different growth media of ethyl acetate and ethanol. The growth rate and thereby solvent inclusions are relatively higher in ethyl acetate grown crystal than the crystal grown from ethanol. The structural, thermal and optical properties of 4-ABP crystals were studied. The enthalpy of 4-ABP melting process was estimated from differential thermal analysis. The optical transmission study shows that 4-ABP crystals grown from ethanol has high transparency compared to ethyl acetate grown sample due to solvent inclusion in the later crystal. PMID:25795606

  19. Effect of solvents on the bulk growth of 4-aminobenzophenone single crystals: A potential material for blue and green lasers

    NASA Astrophysics Data System (ADS)

    Natarajan, V.; Usharani, S.; Arivanandhan, M.; Anandan, P.; Hayakawa, Y.

    2015-06-01

    Although 4-aminobenzophenone (4-ABP) is the best derivative of benzophenone with 260 times higher second harmonic generation (SHG) efficiency than potassium dihydrogen phosphate (KDP), growth of high quality bulk crystal still remains a difficult task. In the present work, the effect of solvents on solubility and growth aspects of 4-ABP was investigated to grow inclusion free 4-ABP crystals. The growth processes were discussed based on solute-solvent interaction in two different growth media of ethyl acetate and ethanol. The growth rate and thereby solvent inclusions are relatively higher in ethyl acetate grown crystal than the crystal grown from ethanol. The structural, thermal and optical properties of 4-ABP crystals were studied. The enthalpy of 4-ABP melting process was estimated from differential thermal analysis. The optical transmission study shows that 4-ABP crystals grown from ethanol has high transparency compared to ethyl acetate grown sample due to solvent inclusion in the later crystal.

  20. Synthesis, growth and characterization of strontium bis (hydrogen L-malate) hexahydrate bulk single crystal: A promising semi-organic nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Senthil, A.; Ramasamy, P.

    2010-01-01

    A potentially useful semi-organic nonlinear optical single crystal of strontium bis (hydrogen L-malate) hexahydrate (SrLM) has been synthesized. Optically good quality bulk single crystal of SrLM was successfully grown by slow cooling technique and Sankaranarayanan—Ramasamy (SR) method. Transparent, colourless crystal of size 24 mm×5 mm×6 mm with well defined morphology was grown by slow cooling method and <010>-oriented unidirectional bulk single crystal of size 50 mm length and 10 mm diameter was grown by the SR method. The unit cell parameters and the morphology of SrLM single crystals were determined by single crystal XRD. The grown crystals were subjected to various characterization studies such as FTIR analysis, UV-visible spectrum, dielectric measurement, DTA, powder SHG test and microhardness studies.

  1. Mid-infrared to ultraviolet optical properties of InSb grown on GaAs by molecular beam epitaxy

    SciTech Connect

    D'Costa, Vijay Richard Yeo, Yee-Chia; Tan, Kian Hua; Jia, Bo Wen; Yoon, Soon Fatt

    2015-06-14

    Spectroscopic ellipsometry was used to investigate the optical properties of an InSb film grown on a GaAs (100) substrate, and to compare the optical properties of InSb film with those of bulk InSb. The film was grown by molecular beam epitaxy under conditions intended to form 90° misfit dislocations at the InSb-GaAs interface. The complex dielectric function obtained in a wide spectroscopic range from 0.06–4.6 eV shows the critical point transitions E{sub 0}, E{sub 1}, E{sub 1} + Δ{sub 1}, E{sub 0}{sup ′}, and E{sub 2}. The amplitudes, energy transitions, broadenings, and phase angles have been determined using a derivative analysis. Comparing film and bulk critical point results reveal that the epitaxial film is nearly relaxed and has bulk-like optical characteristics.

  2. 76 FR 8658 - Bulk Solid Hazardous Materials: Harmonization With the International Maritime Solid Bulk Cargoes...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-15

    ...), 1974, as amended, that carry bulk solid cargoes other than grain. The final rule (75 FR 64586) allows... SECURITY Coast Guard 46 CFR Part 148 RIN 1625-AB47 Bulk Solid Hazardous Materials: Harmonization With the International Maritime Solid Bulk Cargoes (IMSBC) Code AGENCY: Coast Guard, DHS. ACTION: Rule;...

  3. 75 FR 34682 - Bulk Solid Hazardous Materials: Harmonization With the International Maritime Solid Bulk Cargoes...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-18

    ... SECURITY Coast Guard 46 CFR Parts 97 and 148 RIN 1625-AB47 Bulk Solid Hazardous Materials: Harmonization With the International Maritime Solid Bulk Cargoes (IMSBC) Code; Correction AGENCY: Coast Guard, DHS... proposed rule published in the Federal Register on June 17, 2010, entitled ``Bulk Solid Hazardous...

  4. Complex laterally ordered InGaAs and InAs quantum dots by guided self-organized anisotropic strain engineering on shallow- and deep-patterned GaAs (311)B substrates

    SciTech Connect

    Selcuk, E.; Hamhuis, G. J.; Noetzel, R.

    2007-11-01

    Self-organized anisotropic strain engineering guided on shallow- and deep-patterned GaAs (311)B substrates is exploited for formation of complex laterally ordered architectures of connected InGaAs quantum dot (QD) arrays and isolated InAs QD groups by molecular beam epitaxy. The combination of strain and step engineerings on shallow stripe-patterned substrates transforms the periodic spotlike arrangement of the InGaAs QD arrays and InAs QD groups (on planar substrates) into a zigzag arrangement of periodic stripes which are well ordered over macroscopic areas on zigzag mesa-patterned substrates. In contrast, the formation of slow-growing facets on deep-patterned substrates produces QD-free mesa sidewalls, while InGaAs QD arrays and InAs QD groups form on the GaAs (311)B top and bottom planes with arrangements modified only close to the sidewalls depending on the sidewall orientation. The QDs on the shallow- and deep-patterned substrates exhibit excellent optical properties up to room temperature. Therefore, the concept of guided self-organization demonstrated on shallow-patterned (due to steps) and deep-patterned (due to facets) substrates is highlighted for creation of complex architectures of laterally ordered QDs for future quantum functional devices.

  5. Physical vapor transport growth of bulk aluminum nitride crystals

    NASA Astrophysics Data System (ADS)

    Noveski, Vladimir

    The most promising substrates for III-Nitride devices---bulk aluminum nitride (AlN) crystals were grown by seeded and self-seeded methods in sandwich sublimation configuration in nitrogen atmosphere. The growth was performed in an inductively heated reactor, which was designed and assembled during the course of this project. In the theoretical study of mass transfer effects on the crystal growth rate a one-dimensional model was developed assuming diffusion of Al species as rate limiting step. Estimation and validation of model parameters were completed by experiments carried out at temperature 1800--2400°C, pressure 55--105 kPa and temperature gradient in the vapor phase 1--4°C. Crystal growth rates ˜1 mm/h, viable for commercial production and very good uniformity in the plane of growth were achieved. Two typical issues during the seeded growth on SiC were identified: (1) the formation of voids, and (2) the formation of cracks. A viable process window of temperatures, growth times and source-to-seed distances was identified in which these issues could be overcome and single crystalline AIN was deposited on 200--300 mm2 SiC seeds. X-ray diffraction confirmed a single crystalline nature of the grown material, and scanning electron microscopy (SEM) and optical microscopy revealed the step-flow growth mechanism. Grain expansion in the growth direction during self-seeded studies indicated a possibility of achieving single crystalline AlN of significant size starting from a polycrystalline material. Growth interruption and seed preparation were introduced to preserve the crucible integrity and provide conditions for one-dimensional transport. The use of an inverted temperature gradient during initial stages and sintering of the AlN powder source helped eliminating the secondary nucleation, which had been identified to be an issue during the growth on previously polished AlN seeds. X-ray topography and optical microscopy confirmed the epitaxial re-growth after

  6. Cooling by means of passively grown ice

    SciTech Connect

    Gorski, A.; Schertz, W.; Wantroba, A.; Rush, R.; Falkenberg, J.

    1981-01-01

    A solar cooling technique is described that uses ice passively-grown the previous winter. Using heat pipes (thermal syphons), ice is grown and stored in the same container ready for the coming cooling season. This modern adaption of an old cooling technique may have side application both in this country as well as in more northern regions.

  7. Vitamin C content of organically grown produce

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Organically grown produce is the fastest growing sector of fresh market sales in the U.S. While accounting for only 3% of total produce sales, it is growing by 20% per year. There has been much debate over the relative health merits of organically grown fruits and vegetables. Most consumers believ...

  8. Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure.

    PubMed

    Hwang, Beomyong; Hwang, Jeongwoon; Yoon, Jong Keon; Lim, Sungjun; Kim, Sungmin; Lee, Minjun; Kwon, Jeong Hoon; Baek, Hongwoo; Sung, Dongchul; Kim, Gunn; Hong, Suklyun; Ihm, Jisoon; Stroscio, Joseph A; Kuk, Young

    2016-01-01

    Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk. PMID:27503427

  9. Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure

    PubMed Central

    Hwang, Beomyong; Hwang, Jeongwoon; Yoon, Jong Keon; Lim, Sungjun; Kim, Sungmin; Lee, Minjun; Kwon, Jeong Hoon; Baek, Hongwoo; Sung, Dongchul; Kim, Gunn; Hong, Suklyun; Ihm, Jisoon; Stroscio, Joseph A.; Kuk, Young

    2016-01-01

    Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk. PMID:27503427

  10. Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure

    NASA Astrophysics Data System (ADS)

    Hwang, Beomyong; Hwang, Jeongwoon; Yoon, Jong Keon; Lim, Sungjun; Kim, Sungmin; Lee, Minjun; Kwon, Jeong Hoon; Baek, Hongwoo; Sung, Dongchul; Kim, Gunn; Hong, Suklyun; Ihm, Jisoon; Stroscio, Joseph A.; Kuk, Young

    2016-08-01

    Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk.

  11. Exceptional gettering response of epitaxially grown kerfless silicon

    DOE PAGESBeta

    Powell, D. M.; Markevich, V. P.; Hofstetter, J.; Jensen, M. A.; Morishige, A. E.; Castellanos, S.; Lai, B.; Peaker, A. R.; Buonassisi, T.

    2016-02-08

    The bulk minority-carrier lifetime in p- and n-type kerfless epitaxial (epi) crystalline silicon wafers is shown to increase >500 during phosphorus gettering. We employ kinetic defect simulations and microstructural characterization techniques to elucidate the root cause of this exceptional gettering response. Simulations and deep-level transient spectroscopy (DLTS) indicate that a high concentra- tion of point defects (likely Pt) is “locked in” during fast (60 C/min) cooling during epi wafer growth. The fine dispersion of moderately fast-diffusing recombination-active point defects limits as-grown lifetime but can also be removed during gettering, confirmed by DLTS measurements. Synchrotron-based X-ray fluorescence microscopy indicates metal agglomeratesmore » at structural defects, yet the structural defect density is sufficiently low to enable high lifetimes. Consequently, after phosphorus diffusion gettering, epi silicon exhibits a higher lifetime than materials with similar bulk impurity contents but higher densities of structural defects, including multicrystalline ingot and ribbon silicon materials. As a result, device simulations suggest a solar-cell efficiency potential of this material >23%.« less

  12. Exceptional gettering response of epitaxially grown kerfless silicon

    NASA Astrophysics Data System (ADS)

    Powell, D. M.; Markevich, V. P.; Hofstetter, J.; Jensen, M. A.; Morishige, A. E.; Castellanos, S.; Lai, B.; Peaker, A. R.; Buonassisi, T.

    2016-02-01

    The bulk minority-carrier lifetime in p- and n-type kerfless epitaxial (epi) crystalline silicon wafers is shown to increase >500× during phosphorus gettering. We employ kinetic defect simulations and microstructural characterization techniques to elucidate the root cause of this exceptional gettering response. Simulations and deep-level transient spectroscopy (DLTS) indicate that a high concentration of point defects (likely Pt) is "locked in" during fast (60 °C/min) cooling during epi wafer growth. The fine dispersion of moderately fast-diffusing recombination-active point defects limits as-grown lifetime but can also be removed during gettering, confirmed by DLTS measurements. Synchrotron-based X-ray fluorescence microscopy indicates metal agglomerates at structural defects, yet the structural defect density is sufficiently low to enable high lifetimes. Consequently, after phosphorus diffusion gettering, epi silicon exhibits a higher lifetime than materials with similar bulk impurity contents but higher densities of structural defects, including multicrystalline ingot and ribbon silicon materials. Device simulations suggest a solar-cell efficiency potential of this material >23%.

  13. Bulk and surface correlations in a microemulsion

    SciTech Connect

    Lee, D.D.; Chen, S.H.; Majkrzak, C.F.; Satija, S.K.

    1995-07-01

    Small angle neutron scattering and neutron reflectivity are used to study the bulk and surface structure of water--octane--tetraethylene glycol monodecyl ether (C{sub 10}E{sub 4}) bicontinuous microemulsions. When the hydrophilicity and hydrophobicity of the surfactant monolayers in the microemulsion are balanced, the surface correlation length is found to be significantly larger than its bulk analog. Varying the spontaneous curvature of the monolayers greatly influences the surface structure of the microemulsion while having a relatively slight effect on the bulk correlation function. These observations are explained using a Ginzburg-Landau theory.

  14. Bulk modulus for polar covalent crystals

    PubMed Central

    Xu, Bo; Wang, Qianqian; Tian, Yongjun

    2013-01-01

    A microscopic empirical model of bulk modulus based on atomic-scale parameters is proposed. These parameters include the bond length, the effective bonded valence electron (EBVE) number, and the coordination number product of two bonded atoms, etc. The estimated bulk moduli from our model are in good agreement with experimental values for various polar covalent crystals including ionic crystals. Our current work sheds lights on the nature of bulk modulus, provides useful clues for design of crystals with low compressibility, and is applicable to complex crystals such as minerals of geophysical importance. PMID:24166098

  15. Bulk viscosity of a pion gas

    NASA Astrophysics Data System (ADS)

    Lu, Egang; Moore, Guy D.

    2011-04-01

    We compute the bulk viscosity of a gas of pions at temperatures below the QCD crossover temperature, for the physical value of mπ, to lowest order in chiral perturbation theory. Bulk viscosity is controlled by number-changing processes which become exponentially slow at low temperatures when the pions become exponentially dilute, leading to an exponentially large bulk viscosity ζ~(F08/mπ5)exp(2mπ/T), where F0≃93MeV is the pion decay constant.

  16. OSCEE fan exhaust bulk absorber treatment evaluation

    NASA Technical Reports Server (NTRS)

    Bloomer, H. E.; Samanich, N. E.

    1980-01-01

    The acoustic suppression capability of bulk absorber material designed for use in the fan exhaust duct walls of the quiet clean short haul experiment engine (OCSEE UTW) was evaluated. The acoustic suppression to the original design for the engine fan duct which consisted of phased single degree-of-freedom wall treatment was tested with a splitter and also with the splitter removed. Peak suppression was about as predicted with the bulk absorber configuration, however, the broadband characteristics were not attained. Post test inspection revealed surface oil contamination on the bulk material which could have caused the loss in bandwidth suppression.

  17. Imprinting bulk amorphous alloy at room temperature

    SciTech Connect

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.

  18. Imprinting bulk amorphous alloy at room temperature

    PubMed Central

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-01-01

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. Our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment. PMID:26563908

  19. Imprinting bulk amorphous alloy at room temperature.

    PubMed

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T; Lograsso, Thomas A; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-01-01

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. Our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment. PMID:26563908

  20. Zinc Isotope Anomalies in bulk Chondrites

    NASA Astrophysics Data System (ADS)

    Savage, P. S.; Boyet, M.; Moynier, F.

    2014-09-01

    This study is the first to demonstrate that Zn isotope anomalies are present in bulk primitive meteorites, consistent with the injection of material derived from a neutron-rich supernova source into the solar nebula.

  1. Faecal bulking efficacy of Australasian breakfast cereals.

    PubMed

    Monro, John A

    2002-01-01

    Faecal bulk may play an important role in preventing a range of disorders of the large bowel, but as yet there is little information available on the relative faecal bulking capacities of various foods. Breakfast cereals are often promoted as a good source of potential bulk for 'inner health' because they provide dietary fibre, but their relative abilities to provide faecal bulk per se have not been described. The faecal bulking efficacy of 28 representative Australasian breakfast cereals was therefore measured. A rat model developed for the purpose, and shown to give similar responses as humans to cereal fibres, was used to measure faecal bulking efficacy as increases in fully hydrated faecal weight/100 g diet, based on precise measurements of food intake, faecal dry matter output and faecal water-holding capacity (g water held without stress/g faecal dry matter). Compared to a baseline diet containing 50% sucrose, increments in hydrated faecal weight due to 50% breakfast cereal ranged from slightly negative (Cornflakes, -2 g/100 g diet) to about 80 g/100 g diet (San Bran). Most breakfast cereals increased hydrated faecal weight by between 10 and 20 g/100 g diet from a baseline of 21 +/- 1.5 g/100 g diet, but four products containing high levels of wheat bran had an exceptionally large impact on hydrated faecal weight (increment > 20 g/100 g diet), and the changes resulted more from relative changes in dry matter output than in faecal water retention/gram. However, as faecal water retention was about 2.5 g water/g faecal dry matter on average, increases in dry matter represented large increases in faecal water load. Faecal bulking indices (FBI) for most of the breakfast cereals were less than 20 (wheat bran = 100). The content of wheat bran equivalents for faecal bulk (WBE(fb)) in the breakfast cereals was calculated from FBI. Most breakfast cereals contributed, per serve, less than 10% of a theoretical daily reference value for faecal bulk (DRV(fb) = 63 WBE

  2. Bulk growth of high quality nonlinear optical crystals of L-arginine tetrafluoroborate (L-AFB)

    NASA Astrophysics Data System (ADS)

    Owens, C.; Bhat, K.; Wang, W. S.; Tan, A.; Aggarwal, M. D.; Penn, Benjamin G.; Frazier, Donald O.

    2001-05-01

    Bulk single crystals of L-arginine tetrafluoroborate (L-AFB) a new semiorganic nonlinear optical material has been successfully grown from solution by the temperature lowering method. Solubility of L-AFB was measured in various solvents such as ethanol, methanol, acetone and water. L-AFB was found to have extremely low solubility in acetone, ethanol and methanol. Therefore, it was not feasible to grow L-AFB single crystals using these solvents. However, high quality crystals of L-AFB were successfully grown from aqueous solution by the temperature lowering method, even though the mother liqueur became viscous. Large single crystals of L-AFB were grown with dimensions 78×50×35 mm3 in eight weeks. Growth rate and effects of seed orientation on morphologies of L-AFB crystals were studied. L-AFB crystals belong to a class of organic-inorganic complexes in which the high optical nonlinearity of a pure organic compound is combined with the favorable mechanical and thermally stable properties of an inorganic compound. Bulk single crystals of L-AFB are potential materials for applications in blue-green wavelength region.

  3. Growth and optical properties of bulk KTP crystals by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Zhang, Chang-Long; Hu, Zhang-Gui; Huang, Ling-Xiong; Zhou, Wei-Ning; lü, Zhi; Zhang, Ge; Liu, You-Chen; Zou, Yan-Bin; Lu, Fu-Hua; Hou, Hang-De; Qin, Shi-Jie; Zhang, Hai-Xia; Bai, Lang

    2008-04-01

    The high-quality bulk potassium titanyl phosphate (KTiOPO 4 or KTP) crystals have been grown successfully by the hydrothermal method using an improved mixed solution of K 2HPO 4 (2.0 mol/l), KH 2PO 4 (0.1 mol/l) and H 2O 2 (1 wt%) as mineralizer, and spontaneous flux KTP crystals as nutrients. The growing rate of KTP crystals along (0 1 1) was 0.15 mm/day. The size of the biggest grown crystal was up to 26×83×25 mm 3, 132 g in weight. The transmittance was over 80% in the range of 450-2500 nm. The optical homogeneity was up to 4.15×10 -6 cm -1. The precise principal refractive indices were measured by the auto-collimation method and compared with those of KTP grown by the flux method. The Sellmeir equations were fitted with the experimental data. The test of bulk absorption at strong CW green radiation 532 nm was performed with the photo-thermal common-path interferometer. The results showed that the hydrothermal KTP crystals have great ability to anti-gray track.

  4. Orbital magnetization in insulators: Bulk versus surface

    NASA Astrophysics Data System (ADS)

    Bianco, Raffaello; Resta, Raffaele

    2016-05-01

    The orbital magnetic moment of a finite piece of matter is expressed in terms of the one-body density matrix as a simple trace. We address a macroscopic system, insulating in the bulk, and we show that its orbital moment is the sum of a bulk term and a surface term, both extensive. The latter only occurs when the transverse conductivity is nonzero and it is due to conducting surface states. Simulations on a model Hamiltonian validate our theory.

  5. Aluminum nitride bulk crystal growth in a resistively heated reactor

    NASA Astrophysics Data System (ADS)

    Dalmau, Rafael Federico

    A resistively heated reactor capable of temperatures in excess of 2300°C was used to grow aluminum nitride (AlN) bulk single crystals from an AlN powder source by physical vapor transport (PVT) in nitrogen atmosphere. AlN crystals were grown at elevated temperatures by two different methods. Self-seeded crystals were obtained by spontaneous nucleation on the crucible walls, while seeded growth was performed on singular and vicinal (0001) surfaces of silicon carbide (SiC) seeds. During self-seeded growth experiments a variety of crucible materials, such as boron nitride, tungsten, tantalum, rhenium, tantalum nitride, and tantalum carbide, were evaluated. These studies showed that the morphology of crystals grown by spontaneous nucleation strongly depends on the growth temperature and contamination in the reactor. Crucible selection had a profound effect on contamination in the crystal growth environment, influencing nucleation, coalescence, and crystal morphology. In terms of high-temperature stability and compatibility with the growth process, the best results for AlN crystal growth were obtained in crucibles made of sintered tantalum carbide or tantalum nitride. In addition, contamination from the commercially purchased AlN powder source was reduced by presintering the powder prior to growth, which resulted in a drastic reduction of nearly all impurities. Spontaneously grown single crystals up to 15 mm in size were characterized by x-ray diffraction, x-ray topography, glow discharge mass spectrometry, and secondary ion mass spectrometry. Average dislocation densities were on the order of 103 cm -3, with extended areas virtually free of dislocations. High resolution rocking curves routinely showed peak widths as narrow as 7 arcsec, indicating a high degree of crystalline perfection. Low-temperature partially polarized optical reflectance measurements were used to calculate the crystal-field splitting parameter of AlN, Deltacr = -230 meV, and a low-temperature (1

  6. Mechanisms of edge-dislocation formation in strained films of zinc blende and diamond cubic semiconductors epitaxially grown on (001)-oriented substrates

    SciTech Connect

    Bolkhovityanov, Yu. B.; Deryabin, A. S.; Gutakovskii, A. K.; Sokolov, L. V.

    2011-06-15

    Ninety degree edge misfit dislocations (MDs) are 'sessile' dislocations; such dislocations, however, were found in large amounts in relaxed films. The commonly accepted formation mechanism of such dislocations is an interaction of two complementary 60 deg. dislocations with appropriate Burger's vectors, for example: a/2[101] + a/2 [011] = a/2 [110]. In the present study, four possible types of interaction were analyzed: (i) random meeting of two complementary MDs; (ii) crossing of two complementary 60 deg. MDs in the vicinity of film-substrate interface in systems grown on substrates misoriented from exact (001) orientation; (iii) formation of edge MDs during cross-slipping of a secondary MD; and (iv) induced nucleation of a secondary complementary 60 deg. MD. Examples of discussed interactions are given. Contrary to the widespread opinion that edge MDs in GeSi and InGaAs films grown by MBE on Si and GaAs substrates predominantly form under elastic strains greater than 2% and at the final stage of plastic relaxation, in the present study, we show that such dislocations may also form at an early stage of plastic relaxation in films with less-than-1% lattice misfit with substrate. A necessary condition for that is a sufficient amount of 60 deg. dislocations available in the system by the moment the strained film starts growing. Dislocations (60 deg. ) can be introduced into the system using a preliminarily grown, partially or fully relaxed buffer layer. This layer serves as a source of threading dislocations for the next growing layer that favor the formation of paired complementary MDs and their 'reagents', edge MDs, at the interface with growing film.

  7. Short-wavelength infrared imaging using low dark current InGaAs detector arrays and vertical-cavity surface-emitting laser illuminators

    NASA Astrophysics Data System (ADS)

    Macdougal, Michael; Geske, Jon; Wang, Chad; Follman, David

    2011-06-01

    We describe the factors that go into the component choices for a short wavelength IR (SWIR) imager, which include the SWIR sensor, the lens, and the illuminator. We have shown the factors for reducing dark current, and shown that we can achieve well below 1.5 nA/cm2 for 15 μm devices at 7 °C. In addition, we have mated our InGaAs detector arrays to 640×512 readout integrated integrated circuits to make focal plane arrays (FPAs). The resulting FPAs are capable of imaging photon fluxes with wavelengths between 1 and 1.6 μm at low light levels. The dark current associated with these FPAs is extremely low, exhibiting a mean dark current density of 0.26 nA/cm2 at 0 °C. Noise due to the readout can be reduced from 95 to 57 electrons by using off-chip correlated double sampling. In addition, Aerius has developed laser arrays that provide flat illumination in scenes that are normally light-starved. The illuminators have 40% wall-plug efficiency and provide low-speckle illumination, and provide artifact-free imagery versus conventional laser illuminators.

  8. Molecule diagram from space-grown crystals

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Researchers' at Hauptman-Woodward Medical Research Institute, in Buffalo, N.Y. have analyzed the molecular structures of insulin crystals grown during Space Shuttle experiments and are unlocking the mystery of how insulin works.

  9. Predicting bulk damage in NIF triple harmonic generators

    SciTech Connect

    De Yoreo, J; Runkel, M; Williams, W

    1998-09-18

    Recently reported experiments have investigated the statistics of laser damage in KDP and KD*P. Automated damage tests have allowed cumulative failure and damage probability distributions to be constructed. Large area tests have investigated the feasibility of on-line laser conditioning and damage evolution for tripler harmonic generation (THG) crystals on the National Ignition Facility (NIF). These tests have shown that there is a nonzero probability of damage at NIF redline fluence (14.3 J/cm2, 351 nm, 3 ns) and that the damage pinpoint density evolves exponentially with fluence. In this paper, the results of these tests are used in conjunction with model spatial profiles of the NIP beam to predict the level of damage created in the THG crystal. A probabilistic calculation based on the overlap of the beam fluence and damage probabiity distribution shows that the overall damage probability is less than 3% for well-conditioned, high quality KDP/KD*P crystals of conventional or rapid growth. The number density of generated pinpoints has been calculated by mapping the damage evolution curves onto the NlF model profile. This shows that the number of damage pinpoints generated in high fluence portions of the NIF beam will be low for well-conditioned THG crystals. In contrast, unconditioned triplers of the same material will exhibit an increase in pinpoint density of greater than 20x. To test the validity of these calculations a 37 cm, conventionally grown KD*P tripler from the Beamlet laser was scatter mapped for bulk damage. The tripler had been exposed to NE-like fluences during its operational lifetime on Beamlet and exhibited very low levels of bulk pinpoint damage, essentially supporting the predictions based on tests and modeling.

  10. Spontaneous lateral composition modulation in InAlAs and InGaAs short-period superlattices

    SciTech Connect

    Follstaedt, D.M.; Twesten, R.D.; Millunchick, J.M.; Lee, S.R.; Jones, E.D.; Ahrenkiel, S.P.; Zhang, Y.; Mascarenhas, A.

    1997-07-11

    The microstructure of spontaneous lateral composition modulation along the [110] direction has been studied in (InAs){sub n}/(AlAs){sub m} short-period superlattices grown by molecular beam epitaxy on (001) InP. X-ray diffraction and transmission electron microscopy show that global strain ({var_epsilon}) in the superlattice reduces the degree of composition modulation, which disappears for the absolute value of {var_epsilon} > 0.7%. For tensile strains of {var_epsilon} {approx} +0.4%, they find that In-rich columns become regularly spaced and correlated with cusps in the growth surface. A similar correlation is seen in (InAs){sub n}/(GaAs){sub m} short-period superlattices between the enriched columns and the peaks and valleys of {l_brace}114{r_brace}{sub A} facets on the surface. The enriched columns in the (InAs){sub n}/(GaAs){sub m} layer (and the facets) extend for much longer distances ({approximately}0.2--0.4 {micro}m) in the [1{bar 1}0] direction than do the columns in the (InAs){sub n}/(AlAs){sub m} layer ({approximately} 56 nm).

  11. Bulk Fabrication of WS2 Nanoplates: Investigation on the Morphology Evolution and Electrochemical Performance.

    PubMed

    Qian, Jingwen; Peng, Zhijian; Wang, Peilun; Fu, Xiuli

    2016-07-01

    Two-dimensional layered chalcogenide WS2, similar to graphene, is considered to be very interesting for materials scientists. However, to make it a useful material platform, it is necessary to develop sophisticated synthesis methods to control its morphology. In this paper, we present a simple approach to prepare various morphologies of WS2 nanostructures by direct thermal evaporation of WO3 and S powders onto Si substrates sputtered with W film without using any nanostructured W-contained precursors and highly toxic sulfide gases. This method can produce bulk quantities of pure hexagonal, horizontally grown WS2 nanoplates, vertically grown nanoplates, and nanoplate-formed flowers simply by tuning the distance between the substrate and source powders. The synthesis mechanism and morphology evolution model were proposed. Moreover, when employed as a thin-film anode material, the Li-ion battery with as-prepared, vertically grown WS2 nanoplates presented a rechargeable performance between 3 and 0.01 V with a discharge capacity of about 773 mAh/cm(3) after recycling three times, much better than its already-reported counterparts with randomly distributed WS2 nanosheet electrodes, but the battery with horizontally grown WS2 nanoplates could not show any charge-discharge cycling property, which could be attributed to the different structures of WS2 anodes for Li(+) ion intercalation or deintercalation. PMID:27295215

  12. Bulk and interfacial glass transitions of water.

    PubMed

    Bhattacharya, Deepanjan; Payne, Candace N; Sadtchenko, Vlad

    2011-06-16

    Fast scanning calorimetry (FSC) was employed to investigate glass softening dynamics in bulk-like and ultrathin glassy water films. Bulk-like water samples were prepared by vapor-deposition on the surface of a tungsten filament near 140 K where vapor-deposition results in low enthalpy glassy water films. The vapor-deposition approach was also used to grow multiple nanoscale (approximately 50 nm thick) water films alternated with benzene and methanoic films of similar dimensions. When heated from cryogenic temperatures, the ultrathin water films underwent a well manifested glass softening transition at temperatures 20 K below the onset of crystallization. However, no such transition was observed in bulk-like samples prior to their crystallization. These results indicate that thin-film water demonstrates glass softening dynamics that are dramatically distinct from those of the bulk phase. We attribute these differences to water's interfacial glass transition, which occurs at temperatures tens of degrees lower than that in the bulk. Implications of these findings for past studies of glass softening dynamics in various glassy water samples are discussed. PMID:21401034

  13. Module 13: Bulk Packaging Shipments by Highway

    SciTech Connect

    Przybylski, J.L.

    1994-07-01

    The Hazardous Materials Modular Training Program provides participating United States Department of Energy (DOE) sites with a basic, yet comprehensive, hazardous materials transportation training program for use onsite. This program may be used to assist individual program entities to satisfy the general awareness, safety training, and function specific training requirements addressed in Code of Federal Regulation (CFR), Title 49, Part 172, Subpart H -- ``Training.`` Module 13 -- Bulk Packaging Shipments by Highway is a supplement to the Basic Hazardous Materials Workshop. Module 13 -- Bulk Packaging Shipments by Highway focuses on bulk shipments of hazardous materials by highway mode, which have additional or unique requirements beyond those addressed in the ten module core program. Attendance in this course of instruction should be limited to those individuals with work experience in transporting hazardous materials utilizing bulk packagings and who have completed the Basic Hazardous Materials Workshop or an equivalent. Participants will become familiar with the rules and regulations governing the transportation by highway of hazardous materials in bulk packagings and will demonstrate the application of these requirements through work projects and examination.

  14. Bulk Growth of 2-6 Crystals in the Microgravity Environment of USML-1

    NASA Technical Reports Server (NTRS)

    Gillies, Donald C.; Lehoczky, Sandor L.; Szofran, Frank R.; Larson, David J.; Su, Ching-Hua; Sha, Yi-Gao; Alexander, Helga A.

    1993-01-01

    The first United States Microgravity Laboratory Mission (USML- 1) flew in June 1992 on the Space Shuttle Columbia. An important part of this SpaceLab mission was the debut of the Crystal Growth Furnace (CGF). Of the seven samples grown in the furnace, three were bulk grown 2-6 compounds, two of a cadmium zinc telluride alloy, and one of a mercury zinc telluride alloy. Ground based results are presented, together with the results of computer simulated growths of these experimental conditions. Preliminary characterization results for the three USML-1 growth runs are also presented and the flight sample characteristics are compared to the equivalent ground truth samples. Of particular interest are the effect of the containment vessel on surface features, and especially on the nucleation, and the effect of the gravity vector on radial and axial compositional variations and stress and defect levels.

  15. Sensitivity of light-grown and dark-grown Euglena cells to gamma-irradiation.

    PubMed

    Nair, K A; Netrawali, M S

    1979-09-01

    Light-grown cells which contain fully developed chloroplasts were found to be more resistant to gamma-irradiation than dark-grown cells which are devoid of chloroplasts. The radio-resistance of dark-grown cells progressively increased during light-induced development of chloroplasts and, conversely, radio-resistance of light-grown cells decreased progressively with chloroplast de-development during growth in the dark. The presence of chloroplasts seemed to play a major role in the capacity of cells to recover from radiation damage, the efficiency of cellular recovery being correlatable with the degree of chloroplast development. PMID:315395

  16. Sn-doped Bi1.1Sb0.9Te2S bulk crystal topological insulator with excellent properties

    PubMed Central

    Kushwaha, S. K.; Pletikosić, I.; Liang, T.; Gyenis, A.; Lapidus, S. H.; Tian, Yao; Zhao, He; Burch, K. S.; Lin, Jingjing; Wang, Wudi; Ji, Huiwen; Fedorov, A. V.; Yazdani, Ali; Ong, N. P.; Valla, T.; Cava, R. J.

    2016-01-01

    A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high-quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons and be growable as large, high-quality bulk single crystals. Here we show that this material obstacle is overcome by bulk crystals of lightly Sn-doped Bi1.1Sb0.9Te2S grown by the vertical Bridgman method. We characterize Sn-BSTS via angle-resolved photoemission spectroscopy, scanning tunnelling microscopy, transport studies, X-ray diffraction and Raman scattering. We present this material as a high-quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states. PMID:27118032

  17. Sn-doped Bi1.1Sb0.9Te2S bulk crystal topological insulator with excellent properties

    DOE PAGESBeta

    S. K. Kushwaha; Pletikosic, I.; Liang, T.; Gyenis, A.; Lapidus, S. H.; Tian, Y.; Zhao, H.; Burch, K. S.; Lin, Jingjing; Wang, Wudi; et al

    2016-04-27

    A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons, and be growable as large, high quality bulk single crystals. Here we show that this materials obstacle is overcome by bulk crystals of lightly Sn-doped Bi1.1Sb0.9Te2S grown by the Vertical Bridgeman method. We characterize Sn-BSTSmore » via angle-resolved photoemission spectroscopy, scanning tunneling microscopy, transport studies, X-ray diffraction, and Raman scattering. We present this material as a high quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states.« less

  18. Sn-doped Bi1.1Sb0.9Te2S bulk crystal topological insulator with excellent properties

    NASA Astrophysics Data System (ADS)

    Kushwaha, S. K.; Pletikosić, I.; Liang, T.; Gyenis, A.; Lapidus, S. H.; Tian, Yao; Zhao, He; Burch, K. S.; Lin, Jingjing; Wang, Wudi; Ji, Huiwen; Fedorov, A. V.; Yazdani, Ali; Ong, N. P.; Valla, T.; Cava, R. J.

    2016-04-01

    A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high-quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons and be growable as large, high-quality bulk single crystals. Here we show that this material obstacle is overcome by bulk crystals of lightly Sn-doped Bi1.1Sb0.9Te2S grown by the vertical Bridgman method. We characterize Sn-BSTS via angle-resolved photoemission spectroscopy, scanning tunnelling microscopy, transport studies, X-ray diffraction and Raman scattering. We present this material as a high-quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states.

  19. Sn-doped Bi1.1Sb0.9Te2S bulk crystal topological insulator with excellent properties.

    PubMed

    Kushwaha, S K; Pletikosić, I; Liang, T; Gyenis, A; Lapidus, S H; Tian, Yao; Zhao, He; Burch, K S; Lin, Jingjing; Wang, Wudi; Ji, Huiwen; Fedorov, A V; Yazdani, Ali; Ong, N P; Valla, T; Cava, R J

    2016-01-01

    A long-standing issue in topological insulator research has been to find a bulk single crystal material that provides a high-quality platform for characterizing topological surface states without interference from bulk electronic states. This material would ideally be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, display quantum oscillations from the surface state electrons and be growable as large, high-quality bulk single crystals. Here we show that this material obstacle is overcome by bulk crystals of lightly Sn-doped Bi1.1Sb0.9Te2S grown by the vertical Bridgman method. We characterize Sn-BSTS via angle-resolved photoemission spectroscopy, scanning tunnelling microscopy, transport studies, X-ray diffraction and Raman scattering. We present this material as a high-quality topological insulator that can be reliably grown as bulk single crystals and thus studied by many researchers interested in topological surface states. PMID:27118032

  20. Bulk-memory processor for data acquisition

    SciTech Connect

    Nelson, R.O.; McMillan, D.E.; Sunier, J.W.; Meier, M.; Poore, R.V.

    1981-01-01

    To meet the diverse needs and data rate requirements at the Van de Graaff and Weapons Neutron Research (WNR) facilities, a bulk memory system has been implemented which includes a fast and flexible processor. This bulk memory processor (BMP) utilizes bit slice and microcode techniques and features a 24 bit wide internal architecture allowing direct addressing of up to 16 megawords of memory and histogramming up to 16 million counts per channel without overflow. The BMP is interfaced to the MOSTEK MK 8000 bulk memory system and to the standard MODCOMP computer I/O bus. Coding for the BMP both at the microcode level and with macro instructions is supported. The generalized data acquisition system has been extended to support the BMP in a manner transparent to the user.

  1. Topological nonsymmorphic ribbons out of symmorphic bulk

    NASA Astrophysics Data System (ADS)

    Araújo, Augusto L.; Wrasse, Ernesto O.; Ferreira, Gerson J.; Schmidt, Tome M.

    2016-04-01

    States of matter with nontrivial topology have been classified by their bulk symmetry properties. However, by cutting the topological insulator into ribbons, the symmetry of the system is reduced. By constructing effective Hamiltonians containing the proper symmetry of the ribbon, we find that the nature of topological states is dependent on the reduced symmetry of the ribbon and the appropriate boundary conditions. We apply our model to the recently discovered two-dimensional topological crystalline insulators composed by IV-VI monolayers, where we verify that the edge terminations play a major role on the Dirac crossings. Particularly, we find that some bulk cuts lead to nonsymmorphic ribbons, even though the bulk material is symmorphic. The nonsymmorphism yields a new topological protection, where the Dirac cone is preserved for arbitrary ribbon width. The effective Hamiltonians are in good agreement with ab initio calculations.

  2. A stereoscopic look into the bulk

    NASA Astrophysics Data System (ADS)

    Czech, Bartlomiej; Lamprou, Lampros; McCandlish, Samuel; Mosk, Benjamin; Sully, James

    2016-07-01

    We present the foundation for a holographic dictionary with depth perception. The dictionary consists of natural CFT operators whose duals are simple, diffeomorphisminvariant bulk operators. The CFT operators of interest are the "OPE blocks," contributions to the OPE from a single conformal family. In holographic theories, we show that the OPE blocks are dual at leading order in 1 /N to integrals of effective bulk fields along geodesics or homogeneous minimal surfaces in anti-de Sitter space. One widely studied example of an OPE block is the modular Hamiltonian, which is dual to the fluctuation in the area of a minimal surface. Thus, our operators pave the way for generalizing the Ryu-Takayanagi relation to other bulk fields.

  3. Micro benchtop optics by bulk silicon micromachining

    DOEpatents

    Lee, Abraham P.; Pocha, Michael D.; McConaghy, Charles F.; Deri, Robert J.

    2000-01-01

    Micromachining of bulk silicon utilizing the parallel etching characteristics of bulk silicon and integrating the parallel etch planes of silicon with silicon wafer bonding and impurity doping, enables the fabrication of on-chip optics with in situ aligned etched grooves for optical fibers, micro-lenses, photodiodes, and laser diodes. Other optical components that can be microfabricated and integrated include semi-transparent beam splitters, micro-optical scanners, pinholes, optical gratings, micro-optical filters, etc. Micromachining of bulk silicon utilizing the parallel etching characteristics thereof can be utilized to develop miniaturization of bio-instrumentation such as wavelength monitoring by fluorescence spectrometers, and other miniaturized optical systems such as Fabry-Perot interferometry for filtering of wavelengths, tunable cavity lasers, micro-holography modules, and wavelength splitters for optical communication systems.

  4. A diphoton resonance from bulk RS

    NASA Astrophysics Data System (ADS)

    Csáki, Csaba; Randall, Lisa

    2016-07-01

    Recent LHC data hinted at a 750 GeV mass resonance that decays into two photons. A significant feature of this resonance is that its decays to any other Standard Model particles would be too low to be detected so far. Such a state has a compelling explanation in terms of a scalar or a pseudoscalar that is strongly coupled to vector states charged under the Standard Model gauge groups. Such a scenario is readily accommodated in bulk RS with a scalar localized in the bulk away from but close to the Higgs. Turning this around, we argue that a good way to find the elusive bulk RS model might be the search for a resonance with prominent couplings to gauge bosons.

  5. Orchestrating Bulk Data Movement in Grid Environments

    SciTech Connect

    Vazhkudai, SS

    2005-01-25

    Data Grids provide a convenient environment for researchers to manage and access massively distributed bulk data by addressing several system and transfer challenges inherent to these environments. This work addresses issues involved in the efficient selection and access of replicated data in Grid environments in the context of the Globus Toolkit{trademark}, building middleware that (1) selects datasets in highly replicated environments, enabling efficient scheduling of data transfer requests; (2) predicts transfer times of bulk wide-area data transfers using extensive statistical analysis; and (3) co-allocates bulk data transfer requests, enabling parallel downloads from mirrored sites. These efforts have demonstrated a decentralized data scheduling architecture, a set of forecasting tools that predict bandwidth availability within 15% error and co-allocation architecture, and heuristics that expedites data downloads by up to 2 times.

  6. Vacancy compensation and related donor-acceptor pair recombination in bulk AlN

    SciTech Connect

    Gaddy, BE; Bryan, Z; Bryan, I; Kirste, R; Xie, JQ; Dalmau, R; Moody, B; Kumagai, Y; Nagashima, T; Kubota, Y; Kinoshita, T; Koukitu, A; Sitar, Z; Collazo, R; Irving, DL

    2013-10-14

    A prominent 2.8 eV emission peak is identified in bulk AlN substrates grown by physical vapor transport. This peak is shown to be related to the carbon concentration in the samples. Density functional theory calculations predict that this emission is caused by a donor-acceptor pair (DAP) recombination between substitutional carbon on the nitrogen site and a nitrogen vacancy. Photoluminescence and photoluminescence-excitation spectroscopy are used to confirm the model and indicate the DAP character of the emission. The interaction between defects provides a pathway to creating ultraviolet-transparent AlN substrates for optoelectronics applications. (C) 2013 AIP Publishing LLC.

  7. Nuclear Magnetic Resonance Studies of Bulk States of Bi2Se3

    NASA Astrophysics Data System (ADS)

    Nisson, D. M.; Dioguardi, A. P.; Klavins, P.; Lin, C. H.; Shirer, K.; Shockley, A.; Crocker, J.; Curro, N. J.; NMR Group Team

    2013-03-01

    We present 209Bi nuclear magnetic resonance (NMR) spectra and relaxation rate data on single crystals of Bi2Se3 grown under various conditions, whose carrier concentrations, resistivities, and Shubnikov-de Haas (SdH) frequencies have been measured. Our NMR data reveal properties of the bulk states, which are influenced by the presence of intrinsic carriers. We find that both the Knight shift and the electric field gradient of the Bi is correlated with carrier concentration, and atypical spectral profiles. Surprisingly, spin-lattice relaxation is not strongly temperature dependent.

  8. Metal-insulator transition in the Pr substituted Bi-2212 bulk textured crystals

    NASA Astrophysics Data System (ADS)

    Prabhakaran, D.; Subramanian, C.

    1997-02-01

    Bulk textured crystals of Bi 2.2Sr 1.9Ca 1- xPr xCu 2O 8 (0.0 ≤ x ≤ 0.6) were grown by the platinum strip heater floating zone technique. The effect of Pr on the growth and superconducting properties was studied. From the X-ray diffraction studies, variation of lattice constants, phase purity and texturing quantification with respect to Pr substitution were calculated. Variation in the Sr/Ca ratio upon Pr doping was observed. Metal insulator transition was observed in the higher order Pr substituted crystals.

  9. Optical investigation of bulk electron mobility in 3C-SiC films on Si substrates

    NASA Astrophysics Data System (ADS)

    Piluso, N.; Severino, A.; Camarda, M.; Canino, A.; La Magna, A.; La Via, F.

    2010-10-01

    The dependence between the carrier concentration and electrical mobility has been studied by micro-Raman spectroscopy in n-doped 3C-SiC films grown on (111) and (100) Silicon oriented substrates. Bulk mobility varies between 10 and 510 cm2 V-1 s-1 for a carrier concentration ranging between 1.6×1016 and 5.4×1018 cm-3. Local stacking variations observed on the (111) 3C-SiC surface lead to a worse crystal morphology compared to (100) 3C-SiC films resulting in a decrease in the average bulk mobility. Defects are thus accountable for the dependence between mobility and carrier concentration for different 3C-SiC orientations.

  10. Effect of short wavelength illumination on the characteristic bulk diffusion length in ribbon silicon solar cells

    NASA Technical Reports Server (NTRS)

    Ho, C. T.; Mathias, J. D.

    1981-01-01

    The influence of short wavelength light on the characteristic bulk minority carrier diffusion length of the ribbon silicon photovoltaic cell has been investigated. We have measured the intensity and wavelength dependence of the diffusion length in an EFG ribbon cell, and compared it with a standard Czochralski grown silicon cell. While the various short wavelength illuminations have shown no influence on the diffusion length in the CZ cell, the diffusion lengths in the ribbon cell exhibit a strong dependence on the volume generation rate as well as on the wavelength of the superimposed lights. We have concluded that the trap-filling phenomenon at various depths in the bulk neutral region of the cell is consistent with the experimental observation.

  11. Fiber Treatment Effects on Bioreactor Bulk Fluid Trends

    NASA Technical Reports Server (NTRS)

    Ellis, Ronald II

    2013-01-01

    In order to facilitate the exploration of worlds beyond the borders of our planet, it is necessary to maintain sustainable levels of clean water. The remediation of water via Membrane Aerated Bioreactors (MABRs) is one such method, and the focus of this study. MARRs rely on healthy biofilms grown on hollow fiber membranes to clean non-potable water. These biofilms can take weeks to months to establish. Therefore, various fiber treatments and two inoculums were evaluated for their effect on rapid biofilm formation. Fiber treatments are as follows: sanding of the fibers with 1500 and 8000 grit sandpaper, immersion of the fibers in a 1% hydrofluoric acid solution for 12 seconds and 15 minutes, and the immersion of the fibers in a Fluoroetch® solution for 18 seconds and 5 minutes. The two inoculums utilized were sourced from healthy, established MARRs; Texas Tech University (TTU) MABR "TRL5" and Kennedy Space Center (KSC) MABR "R3". Data attained from direct bacterial cell counts of the reactor bulk fluids via fluorescent microscopy, suggests that the fluoroetching treatment combined with the TTU inoculum show the greatest biofilm creation.

  12. Optical Characterization of Bulk ZnSeTe Solid Solutions

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, S.; Zhu, Shen; Lehoczky, S. L.; Wang, Ling Jun

    2000-01-01

    Optical characterization was performed on wafers sliced from crystals of ZnSe, ZnTe, and ZnSe(1-x)Te(x)(0 less than x less than 0.4) grown by physical vapor transport. Energy band gaps at room temperature were determined from optical transmission measurements on 11 wafers. A best fit curve to the band gap versus composition x data gives a bowing parameter of 1.45. This number lies between the value of 1.23 determined previously on ZnSeTe bulk crystals and the value of 1.621 reported on ZnSeTe epilayers. Low-temperature photoluminescence (PL) spectra were measured on six samples. The spectra of ZnSe and ZnTe were dominated by near band edge emissions and no deep donor-acceptor pairs were observed. The PL spectrum exhibited a broad emission for each of the ZnSe(1-x)Te(x) samples, 0.09 less than x less than 0.39. For x=0.09, this emission energy is about 0.2 eV lower than the band gap energy measured at low temperature. As x increases the energy discrepancy gradually decreases and reduces to almost zero at x=0.4. The single broad PL emission spectra and the spectra measured as a function of temperature were interpreted as being associated with the exciton bound to Te clusters because of the high Te content in these samples.

  13. Thermal relics in cosmology with bulk viscosity

    NASA Astrophysics Data System (ADS)

    Iorio, A.; Lambiase, G.

    2015-03-01

    In this paper we discuss some consequences of cosmological models in which the primordial cosmic matter is described by a relativistic imperfect fluid. The latter takes into account the dissipative effects (bulk viscosity) arising from different cooling rates of the fluid components in the expanding Universe. We discuss, in particular, the effects of the bulk viscosity on Big Bang Nucleosynthesis and on the thermal relic abundance of particles, looking at recent results of PAMELA experiment. The latter has determined an anomalous excess of positron events, which cannot be explained by conventional cosmology and particle physics.

  14. Bulk viscosity of multiparticle collision dynamics fluids.

    PubMed

    Theers, Mario; Winkler, Roland G

    2015-03-01

    We determine the viscosity parameters of the multiparticle collision dynamics (MPC) approach, a particle-based mesoscale hydrodynamic simulation method for fluids. We perform analytical calculations and verify our results by simulations. The stochastic rotation dynamics and the Andersen thermostat variant of MPC are considered, both with and without angular momentum conservation. As an important result, we find a nonzero bulk viscosity for every MPC version. The explicit calculation shows that the bulk viscosity is determined solely by the collisional interactions of MPC. PMID:25871248

  15. 'Work-Hardenable' Ductile Bulk Metallic Glass

    SciTech Connect

    Das, Jayanta; Eckert, Juergen; Tang Meibo; Wang Weihua; Kim, Ki Buem; Baier, Falko; Theissmann, Ralf

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive 'work hardening' and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The 'work-hardening' capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  16. Bulk-edge correspondence in topological pumping

    NASA Astrophysics Data System (ADS)

    Hatsugai, Y.; Fukui, T.

    2016-07-01

    The topological pumping proposed in 1980s and recently realized by cold atom experiments is revisited from the view point of the bulk-edge correspondence. For a system with boundaries, a different form of the pumped charge is derived by the Berry connection in the temporal gauge that corresponds to the shift of the center of mass (c.m.). Even with boundaries, the pumped charge is carried by the bulk and its quantization is guaranteed by the discontinuities of the c.m. associated with the edge states. This is a modified Laughlin argument based on the local U (1 ) invariance, although the physics behind it is quite different.

  17. The polarization signature of local bulk flows

    SciTech Connect

    Roebber, Elinore; Holder, Gilbert

    2014-02-01

    A large peculiar velocity of the intergalactic medium produces a Doppler shift of the cosmic microwave background with a frequency-dependent quadrupole term. This quadrupole will act as a source for polarization of the cosmic microwave background, creating a large-scale polarization anisotropy if the bulk flow is local and coherent on large scales. In the case where we are near the center of the moving region, the polarization signal is a pure quadrupole. We show that the signal is small, but detectable with future experiments for bulk flows as large as some recent reports.

  18. 75 FR 64585 - Bulk Solid Hazardous Materials: Harmonization With the International Maritime Solid Bulk Cargoes...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-19

    ...The Coast Guard is harmonizing its regulations with amendments to Chapter VI and Chapter VII of the International Maritime Organization (IMO) International Convention for the Safety of Life at Sea, 1974, as amended, (SOLAS) that make the International Maritime Solid Bulk Cargoes (IMSBC) Code mandatory. The amendments require that all vessels subject to SOLAS, and carrying bulk solid cargoes......

  19. Photoluminescence and hall characterization of pseudomorphic GaAs/InGaAs/AlGaAs heterostructures grown by molecular-beam epitaxy

    SciTech Connect

    Baeta Moreira, M.V.; Py, M.A.; Ilegems, M.

    1993-05-01

    Hall electrical properties measured by the van der Pauw method and low-temperature photoluminescence (77 K PL) spectra of pseudomorphic GaAs/In{sub y}Ga{sub l}-{sub y}As/AlGaAs modulation-doped field-effect transistor-type heterostructures grown by molecular-beam epitaxy were compared. By using these two characterization methods, the influences of the growth temperature T{sub s}, the InGaAs quantum-well channel thickness d{sub ch}, and its indium composition y were studied. interesting correlations were established between their 77 K PL spectra and their transport properties measured either in the dark or under while-light illumination. The PL spectra exhibit one or two bands which are attributed to transitions from electronic states belonging to the first or to the second subband formed in the conductions quantum well, the second transition at higher energy being observed only when the two-dimensional concentration exceeds a critical value n{sub c} which, in the dark, is {approximately} 2.4X10{sup 12} cm{sup {minus}2}(i.e., d{sub ch}{approx}108 {Angstrom}) for the homogeneously doped heterostructures with y=0.25. 27 refs., 10 figs.

  20. Imprinting bulk amorphous alloy at room temperature

    DOE PAGESBeta

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the abilitymore » of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.« less

  1. A stereoscopic look into the bulk

    DOE PAGESBeta

    Czech, Bartlomiej; Lamprou, Lampros; McCandlish, Samuel; Mosk, Benjamin; Sully, James

    2016-07-26

    Here, we present the foundation for a holographic dictionary with depth perception. The dictionary consists of natural CFT operators whose duals are simple, diffeomorphisminvariant bulk operators. The CFT operators of interest are the “OPE blocks,” contributions to the OPE from a single conformal family. In holographic theories, we show that the OPE blocks are dual at leading order in 1/N to integrals of effective bulk fields along geodesics or homogeneous minimal surfaces in anti-de Sitter space. One widely studied example of an OPE block is the modular Hamiltonian, which is dual to the fluctuation in the area of a minimalmore » surface. Thus, our operators pave the way for generalizing the Ryu-Takayanagi relation to other bulk fields. Although the OPE blocks are non-local operators in the CFT, they admit a simple geometric description as fields in kinematic space — the space of pairs of CFT points. We develop the tools for constructing local bulk operators in terms of these non-local objects. The OPE blocks also allow for conceptually clean and technically simple derivations of many results known in the literature, including linearized Einstein’s equations and the relation between conformal blocks and geodesic Witten diagrams.« less

  2. Supramolecular polymer networks: hydrogels and bulk materials.

    PubMed

    Voorhaar, Lenny; Hoogenboom, Richard

    2016-07-21

    Supramolecular polymer networks are materials crosslinked by reversible supramolecular interactions, such as hydrogen bonding or electrostatic interactions. Supramolecular materials show very interesting and useful properties resulting from their dynamic nature, such as self-healing, stimuli-responsiveness and adaptability. Here we will discuss recent progress in polymer-based supramolecular networks for the formation of hydrogels and bulk materials. PMID:27206244

  3. Bulk Density and Soil Moisture Sensors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil bulk density is a good indicator of problems of root penetration, soil aeration, and water infiltration. Knowledge of soil water content is important to understand crop water use, leaching of chemicals, and soil trafficability. The purpose of this presentation is to detail step-by-step how to m...

  4. Teaching Advanced SQL Skills: Text Bulk Loading

    ERIC Educational Resources Information Center

    Olsen, David; Hauser, Karina

    2007-01-01

    Studies show that advanced database skills are important for students to be prepared for today's highly competitive job market. A common task for database administrators is to insert a large amount of data into a database. This paper illustrates how an up-to-date, advanced database topic, namely bulk insert, can be incorporated into a database…

  5. 33 CFR 127.313 - Bulk storage.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) WATERFRONT FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED HAZARDOUS GAS Waterfront Facilities Handling Liquefied Natural Gas Operations § 127.313 Bulk storage. (a) The operator... other fuels in the amount used for one day's operations and maintenance. (b) Flammable liquids must...

  6. 33 CFR 127.313 - Bulk storage.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) WATERFRONT FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED HAZARDOUS GAS Waterfront Facilities Handling Liquefied Natural Gas Operations § 127.313 Bulk storage. (a) The operator... other fuels in the amount used for one day's operations and maintenance. (b) Flammable liquids must...

  7. 33 CFR 127.313 - Bulk storage.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) WATERFRONT FACILITIES WATERFRONT FACILITIES HANDLING LIQUEFIED NATURAL GAS AND LIQUEFIED HAZARDOUS GAS Waterfront Facilities Handling Liquefied Natural Gas Operations § 127.313 Bulk storage. (a) The operator... other fuels in the amount used for one day's operations and maintenance. (b) Flammable liquids must...

  8. 27 CFR 20.182 - Bulk shipments.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bulk shipments. 20.182 Section 20.182 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS DISTRIBUTION AND USE OF DENATURED ALCOHOL AND RUM Operations by Dealers...

  9. The influence of surface preparation on low temperature HfO{sub 2} ALD on InGaAs (001) and (110) surfaces

    SciTech Connect

    Kent, Tyler; Edmonds, Mary; Kummel, Andrew C.; Tang, Kechao; Negara, Muhammad Adi; McIntyre, Paul; Chobpattana, Varistha; Mitchell, William; Sahu, Bhagawan; Galatage, Rohit; Droopad, Ravi

    2015-10-28

    Current logic devices rely on 3D architectures, such as the tri-gate field effect transistor (finFET), which utilize the (001) and (110) crystal faces simultaneously thus requiring passivation methods for the (110) face in order to ensure a pristine 3D surface prior to further processing. Scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and correlated electrical measurement on MOSCAPs were utilized to compare the effects of a previously developed in situ pre-atomic layer deposition (ALD) surface clean on the InGaAs (001) and (110) surfaces. Ex situ wet cleans are very effective on the (001) surface but not the (110) surface. Capacitance voltage indicated the (001) surface with no buffered oxide etch had a higher C{sub max} hypothesized to be a result of poor nucleation of HfO{sub 2} on the native oxide. An in situ pre-ALD surface clean employing both atomic H and trimethylaluminum (TMA) pre-pulsing, developed by Chobpattana et al. and Carter et al. for the (001) surface, was demonstrated to be effective on the (110) surface for producing low D{sub it} high C{sub ox} MOSCAPs. Including TMA in the pre-ALD surface clean resulted in reduction of the magnitude of the interface state capacitance. The XPS studies show the role of atomic H pre-pulsing is to remove both carbon and oxygen while STM shows the role of TMA pre-pulsing is to eliminate H induced etching. Devices fabricated at 120 °C and 300 °C were compared.

  10. Ultra-low noise large-area InGaAs quad photoreceiver with low crosstalk for laser interferometry space antenna

    NASA Astrophysics Data System (ADS)

    Joshi, Abhay; Datta, Shubhashish; Rue, Jim; Livas, Jeffrey; Silverberg, Robert; Guzman Cervantes, Felipe

    2012-07-01

    Quad photoreceivers, namely a 2 x 2 array of p-i-n photodiodes followed by a transimpedance amplifier (TIA) per diode, are required as the front-end photonic sensors in several applications relying on free-space propagation with position and direction sensing capability, such as long baseline interferometry, free-space optical communication, and biomedical imaging. It is desirable to increase the active area of quad photoreceivers (and photodiodes) to enhance the link gain, and therefore sensitivity, of the system. However, the resulting increase in the photodiode capacitance reduces the photoreceiver's bandwidth and adds to the excess system noise. As a result, the noise performance of the front-end quad photoreceiver has a direct impact on the sensitivity of the overall system. One such particularly challenging application is the space-based detection of gravitational waves by measuring distance at 1064 nm wavelength with ~ 10 pm/√Hz accuracy over a baseline of millions of kilometers. We present a 1 mm diameter quad photoreceiver having an equivalent input current noise density of < 1.7 pA/√Hz per quadrant in 2 MHz to 20 MHz frequency range. This performance is primarily enabled by a rad-hard-by-design dualdepletion region InGaAs quad photodiode having 2.5 pF capacitance per quadrant. Moreover, the quad photoreceiver demonstrates a crosstalk of < -45 dB between the neighboring quadrants, which ensures an uncorrected direction sensing resolution of < 50 nrad. The sources of this primarily capacitive crosstalk are presented.

  11. The influence of surface preparation on low temperature HfO2 ALD on InGaAs (001) and (110) surfaces

    NASA Astrophysics Data System (ADS)

    Kent, Tyler; Tang, Kechao; Chobpattana, Varistha; Negara, Muhammad Adi; Edmonds, Mary; Mitchell, William; Sahu, Bhagawan; Galatage, Rohit; Droopad, Ravi; McIntyre, Paul; Kummel, Andrew C.

    2015-10-01

    Current logic devices rely on 3D architectures, such as the tri-gate field effect transistor (finFET), which utilize the (001) and (110) crystal faces simultaneously thus requiring passivation methods for the (110) face in order to ensure a pristine 3D surface prior to further processing. Scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and correlated electrical measurement on MOSCAPs were utilized to compare the effects of a previously developed in situ pre-atomic layer deposition (ALD) surface clean on the InGaAs (001) and (110) surfaces. Ex situ wet cleans are very effective on the (001) surface but not the (110) surface. Capacitance voltage indicated the (001) surface with no buffered oxide etch had a higher Cmax hypothesized to be a result of poor nucleation of HfO2 on the native oxide. An in situ pre-ALD surface clean employing both atomic H and trimethylaluminum (TMA) pre-pulsing, developed by Chobpattana et al. and Carter et al. for the (001) surface, was demonstrated to be effective on the (110) surface for producing low Dit high Cox MOSCAPs. Including TMA in the pre-ALD surface clean resulted in reduction of the magnitude of the interface state capacitance. The XPS studies show the role of atomic H pre-pulsing is to remove both carbon and oxygen while STM shows the role of TMA pre-pulsing is to eliminate H induced etching. Devices fabricated at 120 °C and 300 °C were compared.

  12. The influence of surface preparation on low temperature HfO2 ALD on InGaAs (001) and (110) surfaces.

    PubMed

    Kent, Tyler; Tang, Kechao; Chobpattana, Varistha; Negara, Muhammad Adi; Edmonds, Mary; Mitchell, William; Sahu, Bhagawan; Galatage, Rohit; Droopad, Ravi; McIntyre, Paul; Kummel, Andrew C

    2015-10-28

    Current logic devices rely on 3D architectures, such as the tri-gate field effect transistor (finFET), which utilize the (001) and (110) crystal faces simultaneously thus requiring passivation methods for the (110) face in order to ensure a pristine 3D surface prior to further processing. Scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and correlated electrical measurement on MOSCAPs were utilized to compare the effects of a previously developed in situ pre-atomic layer deposition (ALD) surface clean on the InGaAs (001) and (110) surfaces. Ex situ wet cleans are very effective on the (001) surface but not the (110) surface. Capacitance voltage indicated the (001) surface with no buffered oxide etch had a higher C(max) hypothesized to be a result of poor nucleation of HfO2 on the native oxide. An in situ pre-ALD surface clean employing both atomic H and trimethylaluminum (TMA) pre-pulsing, developed by Chobpattana et al. and Carter et al. for the (001) surface, was demonstrated to be effective on the (110) surface for producing low D(it) high C(ox) MOSCAPs. Including TMA in the pre-ALD surface clean resulted in reduction of the magnitude of the interface state capacitance. The XPS studies show the role of atomic H pre-pulsing is to remove both carbon and oxygen while STM shows the role of TMA pre-pulsing is to eliminate H induced etching. Devices fabricated at 120 °C and 300 °C were compared. PMID:26520547

  13. Inorganic nanostructures grown on graphene layers

    NASA Astrophysics Data System (ADS)

    Park, Won Il; Lee, Chul-Ho; Lee, Jung Min; Kim, Nam-Jung; Yi, Gyu-Chul

    2011-09-01

    This article presents a review of current research activities on the hybrid heterostructures of inorganic nanostructures grown directly on graphene layers, which can be categorized primarily as zero-dimensional nanoparticles; one-dimensional nanorods, nanowires, and nanotubes; and two-dimensional nanowalls. For the hybrid structures, the nanostructures exhibit excellent material characteristics including high carrier mobility and radiative recombination rate as well as long-term stability while graphene films show good optical transparency, mechanical flexibility, and electrical conductivity. Accordingly, the versatile and fascinating properties of the nanostructures grown on graphene layers make it possible to fabricate high-performance optoelectronic and electronic devices even in transferable, flexible, or stretchable forms. Here, we review preparation methods and possible device applications of the hybrid structures consisting of various types of inorganic nanostructures grown on graphene layers.

  14. Differences and similarities between structural properties of GaN grown by different growth methods

    SciTech Connect

    Liliental-Weber, Z.; Jasinski, J.; Washburn, J.

    2002-08-01

    In this paper defects formed in GaN grown by different methods are reviewed. The crystal growth direction and growth rate play important roles. For bulk crystals grown under high pressure the highest growth rates are for planes perpendicular to the c-axis. Only planar defects formed on c-planes are observed in these crystals. There are no threading dislocations or nanotubes in the c-direction. However, polarity of the growth direction plays a role in the surface roughness and the distribution of planar defects. For growth of homo-epitaxial and hetero-epitaxial layers the growth is forced to take place in the much slower c-direction. As a result defects related to the purity of constituents used for growth are formed such as nanotubes and pinholes. In addition threading dislocations and dislocations that accommodate lattice and thermal expansion mismatch are formed.

  15. Photoconductivities in monocrystalline layered V2O5 nanowires grown by physical vapor deposition

    PubMed Central

    2013-01-01

    Photoconductivities of monocrystalline vanadium pentoxide (V2O5) nanowires (NWs) with layered orthorhombic structure grown by physical vapor deposition (PVD) have been investigated from the points of view of device and material. Optimal responsivity and gain for single-NW photodetector are at 7,900 A W-1 and 30,000, respectively. Intrinsic photoconduction (PC) efficiency (i.e., normalized gain) of the PVD-grown V2O5 NWs is two orders of magnitude higher than that of the V2O5 counterpart prepared by hydrothermal approach. In addition, bulk and surface-controlled PC mechanisms have been observed respectively by above- and below-bandgap excitations. The coexistence of hole trapping and oxygen sensitization effects in this layered V2O5 nanostructure is proposed, which is different from conventional metal oxide systems, such as ZnO, SnO2, TiO2, and WO3. PMID:24160337

  16. Photoconductivities in monocrystalline layered V2O5 nanowires grown by physical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, Ruei-San; Wang, Wen-Chun; Chan, Ching-Hsiang; Hsu, Hung-Pin; Tien, Li-Chia; Chen, Yu-Jyun

    2013-10-01

    Photoconductivities of monocrystalline vanadium pentoxide (V2O5) nanowires (NWs) with layered orthorhombic structure grown by physical vapor deposition (PVD) have been investigated from the points of view of device and material. Optimal responsivity and gain for single-NW photodetector are at 7,900 A W-1 and 30,000, respectively. Intrinsic photoconduction (PC) efficiency (i.e., normalized gain) of the PVD-grown V2O5 NWs is two orders of magnitude higher than that of the V2O5 counterpart prepared by hydrothermal approach. In addition, bulk and surface-controlled PC mechanisms have been observed respectively by above- and below-bandgap excitations. The coexistence of hole trapping and oxygen sensitization effects in this layered V2O5 nanostructure is proposed, which is different from conventional metal oxide systems, such as ZnO, SnO2, TiO2, and WO3.

  17. Synthetic mimicking of plant oils and comparison with naturally grown products in polyurethane synthesis.

    PubMed

    Coles, Stuart R; Barker, Guy; Clark, Andrew J; Kirwan, Kerry; Jacobs, Daniel; Makenji, Kylash; Pink, David

    2008-06-11

    The use of plant oils as industrial feedstocks can often be hampered by their lack of optimization towards a particular process, as well as their development being risky; growing suitable volumes of crops to test can take up to five years. To circumvent this, we aimed to discover a method that would mimic plant oil profiles in the laboratory, and show that they exhibited similar properties to the naturally grown plant oils in a given process. Using the synthesis of polyurethanes as an example, we have synthesized six different polymers and demonstrated that plant oils will produce polymers with similar physical properties to those oils mimicked in the laboratory. The use of this mimicking process can be extended to other types of polymers to obtain a method for predicting the properties of a given material based on the plant oil composition of a crop before it is grown in bulk. PMID:18322912

  18. 10Gbps operation of a metamorphic InGaP buffered In 0.53Ga 0.47As p-i-n photodetector grown on GaAs substrate

    NASA Astrophysics Data System (ADS)

    Liao, Yu-Sheng; Lin, Gong-Ru; Lin, Chi-Kuan; Chu, Yi-Shiang; Kuo, Hao-Chung; Feng, Milton

    2005-11-01

    A novel top-illuminated In 0.53Ga 0.47As p-i-n photodiodes (MM-PINPD) grown on GaAs substrate by using a linearly graded metamorphic In xGa 1-xP (x graded from 0.49 to 1) buffer layer has been demonstrated on the SONET OC-192 receiving performance. With a cost-efficient TO-46 package, the MM-PINPD at data rate of 10 Gbit/s can be obtained at minimum optical power of -19.5 dBm. At wavelength of 1550nm, the dark current, optical responsivities, noise equivalent power, and operational bandwidth of the MM-PINPD with aperture diameter of 60 μm are 13 pA, 0.6 A/W, 3.4×10 -15 W/Hz 1/2, and 8 GHz, respectively. All the parameters are comparable to those of similar devices made on InP substrate or other InGaAs products epitaxially grown on an InGaAlAs buffered GaAs substrate. The performances of the MM-PINPD on GaAs are analyzed by impulse injecting of 1.2-ps pulse-train, eye pattern at 10Gbps, and frequency response from VNA.

  19. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Vujisic, L.; Szofran, F. R.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years, especially under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 micrometers, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5 mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 micrometers. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  20. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Motakef, S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years especially, under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 microns, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 microns. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  1. Bulk sulfur (S) deposition in China

    NASA Astrophysics Data System (ADS)

    Liu, Lei; Zhang, Xiuying; Wang, Shanqian; Zhang, Wuting; Lu, Xuehe

    2016-06-01

    A systematic dataset of an observation network on a national scale has been organized to investigate the spatial distribution of bulk sulfur (S) deposition (Sdep) throughout China during 2000-2013, representing by far the most detailed data set to track the bulk sulfur deposition throughout China since 2000. Such a dataset is needed for ecosystem studies and for developing emission control policies. Bulk Sdep values showed great variations, ranging from 2.17 to 70.55 kg ha-1 y-1, with an average of 22.99 kg ha-1 y-1. The average rate of bulk Sdep located in East Coastal region (35.97 kg ha-1 y-1), Middle Yangtze region (57.90 kg ha-1 y-1), Middle Yellow River region (23.42 kg ha-1 y-1), North Coastal region (42.19 kg ha-1 y-1), Northeast region (34.28 kg ha-1 y-1), South Coastal region (36.97 kg S ha-1 y-1), Southwest region (33.85 kg ha-1 y-1) was 4.50, 7.24, 2.93, 5.28, 4.29, 4.63 and 4.24 times than that in Northwest region (7.99 kg ha-1 y-1). Bulk Sdep over China was mainly from fossil fuel combustion (76.96%), biomass burning (7.64%), crust (6.22%), aged sea salt (5.48%) and agriculture (3.68%). A systematic observation network on a national scale should be established to conduct a long-term monitoring atmospheric Sdep (including wet and dry deposition), based on exiting ecological stations administrated by different departments in China.

  2. Effect of the soil type on the microbiome in the rhizosphere of field-grown lettuce

    PubMed Central

    Schreiter, Susanne; Ding, Guo-Chun; Heuer, Holger; Neumann, Günter; Sandmann, Martin; Grosch, Rita; Kropf, Siegfried; Smalla, Kornelia

    2014-01-01

    The complex and enormous diversity of microorganisms associated with plant roots is important for plant health and growth and is shaped by numerous factors. This study aimed to unravel the effects of the soil type on bacterial communities in the rhizosphere of field-grown lettuce. We used an experimental plot system with three different soil types that were stored at the same site for 10 years under the same agricultural management to reveal differences directly linked to the soil type and not influenced by other factors such as climate or cropping history. Bulk soil and rhizosphere samples were collected 3 and 7 weeks after planting. The analysis of 16S rRNA gene fragments amplified from total community DNA by denaturing gradient gel electrophoresis and pyrosequencing revealed soil type dependent differences in the bacterial community structure of the bulk soils and the corresponding rhizospheres. The rhizosphere effect differed depending on the soil type and the plant growth developmental stage. Despite the soil type dependent differences in the bacterial community composition several genera such as Sphingomonas, Rhizobium, Pseudomonas, and Variovorax were significantly increased in the rhizosphere of lettuce grown in all three soils. The number of rhizosphere responders was highest 3 weeks after planting. Interestingly, in the soil with the highest numbers of responders the highest shoot dry weights were observed. Heatmap analysis revealed that many dominant operational taxonomic units were shared among rhizosphere samples of lettuce grown in diluvial sand, alluvial loam, and loess loam and that only a subset was increased in relative abundance in the rhizosphere compared to the corresponding bulk soil. The findings of the study provide insights into the effect of soil types on the rhizosphere microbiome of lettuce. PMID:24782839

  3. Ion implanted epitaxially grown ZnSe

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The epitaxial growth of ZnSe on (100) Ge using the close-spaced transport process is described. Substrate temperature of 575 C and source temperatures of 675 C yield 10 micron, single crystal layers in 10 hours. The Ge substrates provides a nonreplenishable chemical transport agent and the epitaxial layer thickness is limited to approximately 10 microns. Grown epitaxial layers show excellent photoluminescence structure at 77 K. Grown layers exhibit high resistivity, and annealing in Zn vapor at 575 C reduces the resistivity to 10-100 ohms-cm. Zinc vapor annealing quenches the visible photoluminescence.

  4. 27 CFR 19.477 - Use of bulk conveyances.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Use of bulk conveyances... § 19.477 Use of bulk conveyances. If a bulk conveyance meets the construction requirements of § 19.478 or is approved under § 19.473(b), a proprietor may use the bulk conveyance on bonded premises for...

  5. 49 CFR 178.1005 - Flexible Bulk Container identification code.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Flexible Bulk Container identification code. 178... FOR PACKAGINGS Flexible Bulk Container Standards § 178.1005 Flexible Bulk Container identification code. The Flexible Bulk Container code designation is BK3....

  6. 49 CFR 178.1005 - Flexible Bulk Container identification code.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Flexible Bulk Container identification code. 178... FOR PACKAGINGS Flexible Bulk Container Standards § 178.1005 Flexible Bulk Container identification code. The Flexible Bulk Container code designation is BK3....

  7. 49 CFR 178.1015 - General Flexible Bulk Container standards.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false General Flexible Bulk Container standards. 178... FOR PACKAGINGS Flexible Bulk Container Standards § 178.1015 General Flexible Bulk Container standards. (a) Each Flexible Bulk Containers must be sift-proof and completely closed during transport...

  8. 49 CFR 178.1015 - General Flexible Bulk Container standards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false General Flexible Bulk Container standards. 178... FOR PACKAGINGS Flexible Bulk Container Standards § 178.1015 General Flexible Bulk Container standards. (a) Each Flexible Bulk Containers must be sift-proof and completely closed during transport...

  9. 49 CFR 178.1010 - Marking of Flexible Bulk Containers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Marking of Flexible Bulk Containers. 178.1010... PACKAGINGS Flexible Bulk Container Standards § 178.1010 Marking of Flexible Bulk Containers. (a) The manufacturer must: (1) Mark every Flexible Bulk Container in a durable and clearly visible manner. The...

  10. 27 CFR 1.90 - Distilled spirits in bulk.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Distilled spirits in bulk..., NONINDUSTRIAL USE OF DISTILLED SPIRITS AND WINE, BULK SALES AND BOTTLING OF DISTILLED SPIRITS Bulk Sales and Bottling of Distilled Spirits Warehouse Receipts § 1.90 Distilled spirits in bulk. By the terms of the...

  11. Pillar Initiated Growth of High Indium Content Bulk Indium Gallium Nitride to Improve the Material Quality for Photonic Devices

    NASA Astrophysics Data System (ADS)

    McFelea, Heather Dale

    The goal of this research was to reduce dislocations and strain in high indium content bulk InGaN to improve quality for optical devices. In an attempt to achieve this goal, InGaN pillars were grown with compositions that matched the composition of the bulk InGaN grown on top. Pillar height and density were optimized to facilitate coalescence on top of the pillars. It was expected that dislocations within the pillars would bend to side facets, thereby reducing the dislocation density in the bulk overgrowth, however this was not observed. It was also expected that pillars would be completely relaxed at the interface with the substrate. It was shown that pillars are mostly relaxed, but not completely. Mechanisms are proposed to explain why threading dislocations did not bend and how complete relaxation may have been achieved by mechanisms outside of interfacial misfit dislocation formation. Phase separation was not observed by TEM but may be related to the limitations of the sample or measurements. High indium observed at facets and stacking faults could be related to the extra photoluminescence peaks measured. This research focused on the InGaN pillars and first stages of coalescence on top of the pillars, saving bulk growth and device optimization for future research.

  12. Defect structure of a free standing GaN wafer grown by the ammonothermal method

    NASA Astrophysics Data System (ADS)

    Sintonen, Sakari; Suihkonen, Sami; Jussila, Henri; Lipsanen, Harri; Tuomi, Turkka O.; Letts, Edward; Hoff, Sierra; Hashimoto, Tadao

    2014-11-01

    White beam synchrotron radiation X-ray topography (SR-XRT) and X-ray diffraction (XRD) measurements were used to non-destructively study the defect structure of a bulk GaN wafer, grown by the ammonothermal method. SR-XRT topographs revealed high crystal quality with threading dislocation density 8.8×104 cm-2 and granular structure consisting of large, slightly misaligned grains. The threading dislocations within grains were identified as mixed and screw type, while no pure threading edge dislocations were observed.

  13. One-dimensional edge state of Bi thin film grown on Si(111)

    SciTech Connect

    Kawakami, Naoya; Lin, Chun-Liang; Kawai, Maki; Takagi, Noriaki; Arafune, Ryuichi

    2015-07-20

    The geometric and electronic structures of the Bi thin film grown on Si(111) were investigated by using scanning tunneling microscopy and spectroscopy. We have found two types of edges, one of which hosts an electronic state localized one-dimensionally. We also revealed the energy dispersion of the localized edge state from the evolution of quasiparticle interference patterns as a function of energy. These spectroscopic findings well reproduce those acquired for the cleaved surface of the bulk Bi crystal [I. K. Drozdov et al., Nat. Phys. 10, 664 (2014)]. The present results indicate that the deposited Bi film provides a tractable stage for further scrutiny of the one-dimensional edge state.

  14. Bulk solitary waves in elastic solids

    NASA Astrophysics Data System (ADS)

    Samsonov, A. M.; Dreiden, G. V.; Semenova, I. V.; Shvartz, A. G.

    2015-10-01

    A short and object oriented conspectus of bulk solitary wave theory, numerical simulations and real experiments in condensed matter is given. Upon a brief description of the soliton history and development we focus on bulk solitary waves of strain, also known as waves of density and, sometimes, as elastic and/or acoustic solitons. We consider the problem of nonlinear bulk wave generation and detection in basic structural elements, rods, plates and shells, that are exhaustively studied and widely used in physics and engineering. However, it is mostly valid for linear elasticity, whereas dynamic nonlinear theory of these elements is still far from being completed. In order to show how the nonlinear waves can be used in various applications, we studied the solitary elastic wave propagation along lengthy wave guides, and remarkably small attenuation of elastic solitons was proven in physical experiments. Both theory and generation for strain soliton in a shell, however, remained unsolved problems until recently, and we consider in more details the nonlinear bulk wave propagation in a shell. We studied an axially symmetric deformation of an infinite nonlinearly elastic cylindrical shell without torsion. The problem for bulk longitudinal waves is shown to be reducible to the one equation, if a relation between transversal displacement and the longitudinal strain is found. It is found that both the 1+1D and even the 1+2D problems for long travelling waves in nonlinear solids can be reduced to the Weierstrass equation for elliptic functions, which provide the solitary wave solutions as appropriate limits. We show that the accuracy in the boundary conditions on free lateral surfaces is of crucial importance for solution, derive the only equation for longitudinal nonlinear strain wave and show, that the equation has, amongst others, a bidirectional solitary wave solution, which lead us to successful physical experiments. We observed first the compression solitary wave in the

  15. LYCOPENE CONTENT OF ORGANICALLY GROWN TOMATOES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reports on the lycopene content of tomatoes vary widely with country and source of fruit (field, greenhouse, retail). This study was done to compare the lycopene content of organically grown tomatoes, and to compare fully red fruit to those ripened after harvest. Thirteen tomato cultivars (12 beef...

  16. Efflux Of Nitrate From Hydroponically Grown Wheat

    NASA Technical Reports Server (NTRS)

    Huffaker, R. C.; Aslam, M.; Ward, M. R.

    1992-01-01

    Report describes experiments to measure influx, and efflux of nitrate from hydroponically grown wheat seedlings. Ratio between efflux and influx greater in darkness than in light; increased with concentration of nitrate in nutrient solution. On basis of experiments, authors suggest nutrient solution optimized at lowest possible concentration of nitrate.

  17. Molecule diagram from earth-grown crystals

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Like many chemicals in the body, the three-dimensional structure of insulin is extremely complex. When grown on the ground, insulin crystals do not grow as large or as ordered as researchers desire--obscuring the blueprint of the insulin molecules.

  18. Grown-ups Ought To Know Better.

    ERIC Educational Resources Information Center

    Brightman, Samuel C.

    Among the articles by Sam Brightman collected in this volume from the newsletter, "Adult & Continuing Education Today (ACET)" are the following: "Grown-Ups Ought to Know Better"; "Adult Education: The Only Sure Factor Is Growth"; "Adult Education Important in This Election Year"; "Will Nursery School External Degree Programs Come Next?";…

  19. Origin of Anomalous Piezoresistive Effects in VLS Grown Si Nanowires

    PubMed Central

    2015-01-01

    Although the various effects of strain on silicon are subject of intensive research since the 1950s the physical background of anomalous piezoresistive effects in Si nanowires (NWs) is still under debate. Recent investigations concur in that due to the high surface-to-volume ratio extrinsic surface related effects superimpose the intrinsic piezoresistive properties of nanostructures. To clarify this interplay of piezoresistive effects and stress related surface potential modifications, we explored a particular tensile straining device (TSD) with a monolithic embedded vapor–liquid–solid (VLS) grown Si NW. Integrating the suspended NW in a gate all around (GAA) field effect transistor (FET) configuration with a transparent gate stack enables optical and field modulated electrical characterization under high uniaxial tensile strain applied along the ⟨111⟩ Si NW growth direction. A model based on stress-induced carrier mobility change and surface charge modulation is proposed to interpret the actual piezoresistive behavior of Si NWs. By controlling the nature and density of surface states via passivation the “true” piezoresistance of the NWs is found to be comparable with that of bulk Si. This demonstrates the indispensability of application-specific NW surface conditioning and the modulation capability of Si NWs properties for sensor applications. PMID:25651106

  20. Origin of anomalous piezoresistive effects in VLS grown Si nanowires.

    PubMed

    Winkler, Karl; Bertagnolli, Emmerich; Lugstein, Alois

    2015-03-11

    Although the various effects of strain on silicon are subject of intensive research since the 1950s the physical background of anomalous piezoresistive effects in Si nanowires (NWs) is still under debate. Recent investigations concur in that due to the high surface-to-volume ratio extrinsic surface related effects superimpose the intrinsic piezoresistive properties of nanostructures. To clarify this interplay of piezoresistive effects and stress related surface potential modifications, we explored a particular tensile straining device (TSD) with a monolithic embedded vapor-liquid-solid (VLS) grown Si NW. Integrating the suspended NW in a gate all around (GAA) field effect transistor (FET) configuration with a transparent gate stack enables optical and field modulated electrical characterization under high uniaxial tensile strain applied along the ⟨111⟩ Si NW growth direction. A model based on stress-induced carrier mobility change and surface charge modulation is proposed to interpret the actual piezoresistive behavior of Si NWs. By controlling the nature and density of surface states via passivation the "true" piezoresistance of the NWs is found to be comparable with that of bulk Si. This demonstrates the indispensability of application-specific NW surface conditioning and the modulation capability of Si NWs properties for sensor applications. PMID:25651106

  1. Effects of annealing in N2 ambient on traps and persistent conduction in hydrothermally grown ZnO

    NASA Astrophysics Data System (ADS)

    Fang, Z.-Q.; Claflin, B.; Look, D. C.

    2008-04-01

    Thermally stimulated current (TSC) spectroscopy and temperature-dependent dark current (DC) measurements have been applied to study traps and photoinduced persistent surface conduction in two hydrothermally grown bulk ZnO samples, as-grown, and annealed at 600°C in N2 ambient for 30min, respectively. The as-grown sample had a room-temperature (RT) resistivity of 1.6×103Ωcm, mobility of 2.1×102cm2/Vs, and carrier concentration of 1.8×1013cm-3, while the annealed sample was highly resistive, with RT resistivity of 3.6×106Ωcm, mobility of 4.4cm2/Vs, and carrier concentration of 3.9×1011cm-3. The as-grown sample showed strong conduction at low temperatures, which has been shown to be due to near-surface carriers in other studies. The annealed sample did not demonstrate this phenomenon. The dominant trap in the as-grown sample had an activation energy of 0.16eV, was strongest near the surface, and is possibly related to VZn. In the annealed sample, however, the dominant trap had an activation energy of 0.22eV, was of bulk nature, and is tentatively assigned to LiZn. After several routine TSC measurements, the DC for the as-grown sample increased by more than one order of magnitude at low temperatures (T<180K), while for the annealed sample, the DC increased by a factor of 2 at high temperatures (T>200K). These effects are generated by the TSC trap-filling illumination and can persist for many days under vacuum. At RT, the DC in the annealed sample returns to its equilibrium state if the sample is vented to air.

  2. Combinatorial development of bulk metallic glasses.

    PubMed

    Ding, Shiyan; Liu, Yanhui; Li, Yanglin; Liu, Ze; Sohn, Sungwoo; Walker, Fred J; Schroers, Jan

    2014-05-01

    The identification of multicomponent alloys out of a vast compositional space is a daunting task, especially for bulk metallic glasses composed of three or more elements. Despite an increasing theoretical understanding of glass formation, bulk metallic glasses are predominantly developed through a sequential and time-consuming trial-and-error approach. Even for binary systems, accurate quantum mechanical approaches are still many orders of magnitude away from being able to simulate the relatively slow kinetics of glass formation. Here, we present a high-throughput strategy where ∼3,000 alloy compositions are fabricated simultaneously and characterized for thermoplastic formability through parallel blow forming. Using this approach, we identified the composition with the highest thermoplastic formability in the glass-forming system Mg-Cu-Y. The method provides a versatile toolbox for unveiling complex correlations of material properties and glass formation, and should facilitate a drastic increase in the discovery rate of metallic glasses. PMID:24728462

  3. Foamed Bulk Metallic Glass (Foam) Investigation

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This soldering iron has an evacuated copper capsule at the tip that contains a pellet of Bulk Metallic Glass (BMG) aboard the International Space Station (ISS). Prior to flight, researchers sealed a pellet of bulk metallic glass mixed with microscopic gas-generating particles into the copper ampoule under vacuum. Once heated in space, such as in this photograph, the particles generated gas and the BMG becomes a viscous liquid. The released gas made the sample foam within the capsule where each microscopic particle formed a gas-filled pore within the foam. The inset image shows the oxidation of the sample after several minutes of applying heat. Although hidden within the brass sleeve, the sample retained the foam shape when cooled, because the viscosity increased during cooling until it was solid.

  4. Bulk band gaps in divalent hexaborides

    SciTech Connect

    Denlinger, Jonathan; Clack, Jules A.; Allen, James W.; Gweon, Gey-Hong; Poirier, Derek M.; Olson, Cliff G.; Sarrao, John L.; Bianchi, Andrea D.; Fisk, Zachary

    2002-08-01

    Complementary angle-resolved photoemission and bulk-sensitive k-resolved resonant inelastic x-ray scattering of divalent hexaborides reveal a >1 eV X-point gap between the valence and conduction bands, in contradiction to the band overlap assumed in several models of their novel ferromagnetism. This semiconducting gap implies that carriers detected in transport measurements arise from defects, and the measured location of the bulk Fermi level at the bottom of the conduction band implicates boron vacancies as the origin of the excess electrons. The measured band structure and X-point gap in CaB6 additionally provide a stringent test case for proper inclusion of many-body effects in quasi-particle band calculations.

  5. Surface-Bulk Vibrational Correlation Spectroscopy.

    PubMed

    Roy, Sandra; Covert, Paul A; Jarisz, Tasha A; Chan, Chantelle; Hore, Dennis K

    2016-05-01

    Homo- and heterospectral correlation analysis are powerful methods for investigating the effects of external influences on the spectra acquired using distinct and complementary techniques. Nonlinear vibrational spectroscopy is a selective and sensitive probe of surface structure changes, as bulk molecules are excluded on the basis of symmetry. However, as a result of this exquisite specificity, it is blind to changes that may be occurring in the solution. We demonstrate that correlation analysis between surface-specific techniques and bulk probes such as infrared absorption or Raman scattering may be used to reveal additional details of the adsorption process. Using the adsorption of water and ethanol binary mixtures as an example, we illustrate that this provides support for a competitive binding model and adds new insight into a dimer-to-bilayer transition proposed from previous experiments and simulations. PMID:27058265

  6. Cosmological two-fluid bulk viscosity

    NASA Astrophysics Data System (ADS)

    van den Horn, L. J.; Salvati, G. A. Q.

    2016-04-01

    A simple two-fluid model of cosmological bulk viscosity, in which small deviations from thermal equilibrium account for the viscous bulk pressure, is substantiated by kinetic theory. Some peculiar issues regarding its relation to the radiative fluid model are discussed. The microphysical picture underlying the viscous dissipation is made precise. We also consider a reactive `cross' viscosity associated with deviations from detailed balance, which includes the so-called creation pressure of the cosmological fluid. For collisional interactions between the fluid components, the reactive viscous pressure is not an independent mechanism for entropy production. Entropy from cross effects may be generated through an effective isentropic particle source. In both instances new results are obtained for the reactive viscosity, and applied to a representative case of non-equilibrium decay.

  7. Microfabricated bulk wave acoustic bandgap device

    DOEpatents

    Olsson, Roy H.; El-Kady, Ihab F.; McCormick, Frederick; Fleming, James G.; Fleming, Carol

    2010-06-08

    A microfabricated bulk wave acoustic bandgap device comprises a periodic two-dimensional array of scatterers embedded within the matrix material membrane, wherein the scatterer material has a density and/or elastic constant that is different than the matrix material and wherein the periodicity of the array causes destructive interference of the acoustic wave within an acoustic bandgap. The membrane can be suspended above a substrate by an air or vacuum gap to provide acoustic isolation from the substrate. The device can be fabricated using microelectromechanical systems (MEMS) technologies. Such microfabricated bulk wave phononic bandgap devices are useful for acoustic isolation in the ultrasonic, VHF, or UHF regime (i.e., frequencies of order 1 MHz to 10 GHz and higher, and lattice constants of order 100 .mu.m or less).

  8. Microfabricated bulk wave acoustic bandgap device

    DOEpatents

    Olsson, Roy H.; El-Kady, Ihab F.; McCormick, Frederick; Fleming, James G.; Fleming, legal representative, Carol

    2010-11-23

    A microfabricated bulk wave acoustic bandgap device comprises a periodic two-dimensional array of scatterers embedded within the matrix material membrane, wherein the scatterer material has a density and/or elastic constant that is different than the matrix material and wherein the periodicity of the array causes destructive interference of the acoustic wave within an acoustic bandgap. The membrane can be suspended above a substrate by an air or vacuum gap to provide acoustic isolation from the substrate. The device can be fabricated using microelectromechanical systems (MEMS) technologies. Such microfabricated bulk wave phononic bandgap devices are useful for acoustic isolation in the ultrasonic, VHF, or UHF regime (i.e., frequencies of order 1 MHz to 10 GHz and higher, and lattice constants of order 100 .mu.m or less).

  9. Premelting at Defects Within Bulk Colloidal Crystals

    NASA Astrophysics Data System (ADS)

    Alsayed, A. M.; Islam, M. F.; Zhang, J.; Collings, P. J.; Yodh, A. G.

    2005-08-01

    Premelting is the localized loss of crystalline order at surfaces and defects at temperatures below the bulk melting transition. It can be thought of as the nucleation of the melting process. Premelting has been observed at the surfaces of crystals but not within. We report observations of premelting at grain boundaries and dislocations within bulk colloidal crystals using real-time video microscopy. The crystals are equilibrium close-packed, three-dimensional colloidal structures made from thermally responsive microgel spheres. Particle tracking reveals increased disorder in crystalline regions bordering defects, the amount of which depends on the type of defect, distance from the defect, and particle volume fraction. Our observations suggest that interfacial free energy is the crucial parameter for premelting in colloidal and atomic-scale crystals.

  10. Effective pure states for bulk quantum computation

    SciTech Connect

    Knill, E.; Chuang, I.; Laflamme, R.

    1997-11-01

    In bulk quantum computation one can manipulate a large number of indistinguishable quantum computers by parallel unitary operations and measure expectation values of certain observables with limited sensitivity. The initial state of each computer in the ensemble is known but not pure. Methods for obtaining effective pure input states by a series of manipulations have been described by Gershenfeld and Chuang (logical labeling) and Corey et al. (spatial averaging) for the case of quantum computation with nuclear magnetic resonance. We give a different technique called temporal averaging. This method is based on classical randomization, requires no ancilla qubits and can be implemented in nuclear magnetic resonance without using gradient fields. We introduce several temporal averaging algorithms suitable for both high temperature and low temperature bulk quantum computing and analyze the signal to noise behavior of each.

  11. Combinatorial development of bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Ding, Shiyan; Liu, Yanhui; Li, Yanglin; Liu, Ze; Sohn, Sungwoo; Walker, Fred J.; Schroers, Jan

    2014-05-01

    The identification of multicomponent alloys out of a vast compositional space is a daunting task, especially for bulk metallic glasses composed of three or more elements. Despite an increasing theoretical understanding of glass formation, bulk metallic glasses are predominantly developed through a sequential and time-consuming trial-and-error approach. Even for binary systems, accurate quantum mechanical approaches are still many orders of magnitude away from being able to simulate the relatively slow kinetics of glass formation. Here, we present a high-throughput strategy where ˜3,000 alloy compositions are fabricated simultaneously and characterized for thermoplastic formability through parallel blow forming. Using this approach, we identified the composition with the highest thermoplastic formability in the glass-forming system Mg-Cu-Y. The method provides a versatile toolbox for unveiling complex correlations of material properties and glass formation, and should facilitate a drastic increase in the discovery rate of metallic glasses.

  12. The Soret effect in bulk metallic glasses

    SciTech Connect

    Liu, Yong; Liu, Chain T; George, Easo P; Wang, Xianzhen

    2007-01-01

    Compositional inhomogeneity induced by the Soret effect was studied in two Zr-based bulk metallic glasses (BMG): Zr50Cu50 and Zr50Cu40Al10 (at.%), and one Cu-based BMG: Cu60Zr30Ti10 (at.%), all of which were prepared by rapid solidification. The concentration of Cu increases from the surface to the interior, while the concentrations of Zr, Ti and Al decrease. The magnitude of the Soret effect is found to be highly dependant on sample size and interactions between the diffusing atoms in bulk metallic glasses. For the Zr50Cu50 alloy, a large sample size favors the Soret effect, because of the longer diffusion time it affords compared to a small sample. Further, the additions of Al and Ti in the Zr-Cu BMGs reduce the magnitude of the Soret effect by the formation of short-range order and/or inter-atomic clusters.

  13. Bulk locality and boundary creating operators

    NASA Astrophysics Data System (ADS)

    Nakayama, Yu; Ooguri, Hirosi

    2015-10-01

    We formulate a minimum requirement for CFT operators to be localized in the dual AdS. In any spacetime dimensions, we show that a general solution to the requirement is a linear superposition of operators creating spherical boundaries in CFT, with the dilatation by the imaginary unit from their centers. This generalizes the recent proposal by Miyaji et al. for bulk local operators in the three dimensional AdS. We show that Ishibashi states for the global conformal symmetry in any dimensions and with the imaginary di-latation obey free field equations in AdS and that incorporating bulk interactions require their superpositions. We also comment on the recent proposals by Kabat et al., and by H. Verlinde.

  14. Induction detection of concealed bulk banknotes

    NASA Astrophysics Data System (ADS)

    Fuller, Christopher; Chen, Antao

    2012-06-01

    The smuggling of bulk cash across borders is a serious issue that has increased in recent years. In an effort to curb the illegal transport of large numbers of paper bills, a detection scheme has been developed, based on the magnetic characteristics of bank notes. The results show that volumes of paper currency can be detected through common concealing materials such as plastics, cardboard, and fabrics making it a possible potential addition to border security methods. The detection scheme holds the potential of also reducing or eliminating false positives caused by metallic materials found in the vicinity, by observing the stark difference in received signals caused by metal and currency. The detection scheme holds the potential to detect for both the presence and number of concealed bulk notes, while maintaining the ability to reduce false positives caused by metal objects.

  15. Structural rejuvenation in bulk metallic glasses

    DOE PAGESBeta

    Tong, Yang; Iwashita, T.; Dmowski, Wojciech; Bei, Hongbin; Yokoyama, Y.; Egami, Takeshi

    2015-01-05

    Using high-energy X-ray diffraction we study structural changes in bulk metallic glasses after uniaxial compressive homogeneous deformation at temperatures slightly below the glass transition. We observe that deformation results in structural disordering corresponding to an increase in the fictive, or effective, temperature. However, the structural disordering saturates after yielding. Lastly, examination of the experimental structure and molecular dynamics simulation suggests that local changes in the atomic connectivity network are the main driving force of the structural rejuvenation.

  16. Formation of bulk metallic glass by fluxing

    NASA Technical Reports Server (NTRS)

    Kui, H. W.; Turnbull, D.; Greer, A. L.

    1984-01-01

    Bulk specimens (0.4-4 g mass) of the alloy Pd40Ni40P20 have been undercooled consistently to the glass state, with no detectable superficial crystallinity, in a molten flux of dehydrated boron oxide. The minimum dimension of the most massive glass specimen, so formed, was 1.0 cm. The absence of crystallinity in the specimens was confirmed by X-ray diffraction, scanning electron microscopy, and calorimetry.

  17. Solid State Processing of Bulk Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Eckert, Jurgen

    1998-03-01

    Glasses are generally produced from the undercooled liquid state by rapid quenching methods or quasi-statically at slow cooling by the effective control of heterogeneous nucleation. For metallic systems, the latter method has recently led to the development of multicomponent metallic glasses with large glass forming ability and a wide supercooled liquid region before crystallization. Large-scale bulk samples can now be produced by conventional casting techniques. These materials exhibit advanced engineering properties such as excellent wear behavior, almost theoretical strength and good corrosion resistance, and are highly processable at temperatures above the glass transition temperature. As an alternative to quenching or casting techniques, glass formation can also be achieved by solid state processing without passing through the liquid state. Therefore, mechanical alloying as a special form of solid state reaction technique and subsequent consolidation of the resulting powders above the glass transition temperature can be used to prepare bulk metallic glasses through the powder metallurgy route. This paper surveys results of studies regarding the factors governing glass formation by solid state processing. The thermal stability of mechanically alloyed powders is compared with data for melt quenched samples, showing that basically the same glassy state can be reached approaching it from the liquid or the solid state. Special emphasis is given to the glass forming ranges achievable by the different techniques, and to preparation of nanostructured composite materials based on glassy alloys. The results are discussed with respect to the influence of processing conditions, impurity effects and heterogeneous nucleation of crystalline phases. Examples for consolidated bulk samples from mechanically alloyed powders are presented and compared with data for cast bulk specimens.

  18. Seven New Bulk Chemical Analyses of Aubrites

    NASA Astrophysics Data System (ADS)

    Easton, A. J.

    1985-09-01

    New bulk chemical analyses are given of Aubres, Bishopville, Bustee, Khor Temiki, Norton County, Peña Blanca Spring and Shallowater. Selective attack by dry chlorine (350°C) on magnetic and non-magnetic fractions was used to determine the distribution of some normally lithophile elements (Al, Ca, Cr, K, Mg, Mn, Na, P and Ti) between silicate and sulphide groups of minerals.

  19. Bulk-titanium for MEMS switches

    NASA Astrophysics Data System (ADS)

    Ding, Changsong

    RF-MEMS switches offer great potential benefits such as high isolation, low insertion loss, low power consumption, and excellent linearity characteristics. Most MEMS switches are fabricated using surface micromachining techniques by taking advantage of the IC processing techniques. Little work has been done on bulk micromachining for fabricating MEMS switches. This work contributes to two main areas in the MEMS switch field, (1) a Sacrificial-Layer-Free (SLF) method to fabricate switches using bulk titanium MEMS (BT-MEMS) and multilayer lamination techniques, and (2) development of a novel composite contact material and integration into BT-MEMS switches for testing. This approach for fabricating MEMS switches offers advantages from five aspects to attack the fabrication and reliability issues. Four generations of Bulk-Ti MEMS (BT-MEMS) switches were developed. They were improved through developments of high aspect ratio bulk Ti etching, Titanium-On-Insulator structure, multilayer lamination, mechanical design, and a new contact material. The first generation proved the feasibility of the concept of the BT-MEMS switch. The second generation had a good contact resistance. Development of the novel Nano-Structured-Titania (NST) composite material allowed further improvement of the third generation. We used the BT-MEMS switch as a platform for testing this new, novel contact material. Due to the preferred surface properties of the NST-metal composite material such as roughness and hardness, the third generation switched above 15 billion contact cycles without adhesion failure. Contact resistance was further improved in the fourth generation switch by integrating the NST-metal composite material into the top part as bumps. Above 100 million cycles with good contact resistance values were achieved.

  20. The effect of nitridation and sulfur passivation for In0.53Ga0.47As surfaces on their Al/Al2O3/InGaAs MOS capacitors properties

    NASA Astrophysics Data System (ADS)

    Zizeng, Lin; Mingmin, Cao; Shengkai, Wang; Qi, Li; Gongli, Xiao; Xi, Gao; Honggang, Liu; Haiou, Li

    2016-02-01

    The impact of nitridation and sulfur passivation for In0 53Ga0 47As surfaces on the Al/Al2O3/InGaAs MOS capacitors properties was investigated by comparing the characteristics of frequency dispersion and hysteresis, calculating the Dit and ΔNbt values, and analyzing the interface traps and the leakage current. The results showed that both of the methods could form a passivation-layer on the InGaAs surface. The samples treated by N2 plasma could obtain good interface properties with the smallest frequency dispersion in the accumulation region, and the best hysteresis characteristics and good I-V properties were presented. Also the samples with (NH4/2Sx treatment showed the smallest frequency dispersion near the flat-band region and a minimum Dit value of 2.6 × 1011 cm-2 eV-1. Project supported by the National Natural Science Foundation of China (Nos. 61274077, 61474031, 61464003), the Guangxi Natural Science Foundation (Nos. 2013GXNSFGA019003, 2013GXNSFAA019335), the Project (No. 9140C140101140C14069), the Innovation Project of GUET Graduate Education (No. YJCXS201529), and the National Science & Technology Major Project of China (No. 2011ZX02708-003).