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  • American Institute of Physics (AIP)  (49)
  • Public Library of Science (PLoS)
  • 1990-1994  (49)
  • 1
    Digitale Medien
    Digitale Medien
    Carbon incorporation in InP grown by metalorganic chemical vapor deposition and application to InP/InGaAs heterojunction bipolar transistors (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4233-4236 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The incorporation of residual carbon has been studied for InP grown at low temperatures using TMIn and PH3 by low-pressure metalorganic chemical vapor deposition. n-type conduction is observed with electron concentrations as high as 1×1018 cm−3, and the electrical activation efficiency is 5%–15%. Carbon incorporation is found to be highly dependent on substrate temperature, suggesting that the rate-limiting step is desorption of CHy (0≤y≤3) from the surface during growth. Hydrogen is also incorporated in the layers during growth. The electron mobilities are lower for C-doped InP than for Si-doped InP. InP/InGaAs heterojunction bipolar transistors with C as the p-type base dopant and either Si or C as the n-type emitter dopant have been fabricated and compared. Devices with a carbon-doped base and emitter showed degraded performance, likely as a result of deep levels incorporated during growth of the emitter.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.356011
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  • 2
    Digitale Medien
    Digitale Medien
    The effect of grid quality and weight derivatives in density functional calculations (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 8894-8902 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Full density functional geometry optimizations on hydrogen peroxide and heptane/dimethyl pentane using six different numerical grids are presented. The grids vary in quality and gradients are calculated (1) assuming a fixed grid and no weight derivatives, and (2) with full allowance for a "moving'' atom-centered grid and inclusion of the weight derivatives. The results clearly demonstrate that accurate energies and geometries can be obtained with around 3500 points per atom for medium-sized systems (up to say 30 atoms) without the necessity of including the weight derivatives. The latter only begin to influence the results for grids which are of insufficient quality to guarantee reliable values in any case.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.468081
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  • 3
    Digitale Medien
    Digitale Medien
    The chemical potential in atomically inhomogeneous fluids in external force fields by computer simulation (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4098-4102 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The accuracy and practicality of the Widom fictitious-particle insertion method for determining the chemical potential is tested for very inhomogeneous fluids in strong external potentials by a series of molecular dynamics computer simulations. The chemical potential determined in this way is found, as predicted, on an atomic scale to be independent of position in the fluid to a few percent even when the density varies by up to a factor 80. This severe test means that this method of determining chemical potential is established as reliable and accurate in any well-found computer simulation even when the system is very inhomogeneous.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.467527
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  • 4
    Digitale Medien
    Digitale Medien
    Shear cell for the study of liquid-solid interfaces by neutron scattering (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 412-416 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A cell for examining the density profile of sheared fluids at the solid-liquid interface by neutron reflectometry is presented. This cell has also proven valuable in examining near-surface bulk structures in the plane perpendicular to the shear flow using small angle neutron scattering. The shear rates can be controlled by changing the volume flow through the cell over three orders of magnitude. All components of the cell are designed to be chemically inert. A temperature-controlled environment compatible with neutron studies is also briefly described. Preliminary neutron reflectivity and small angle neutron scattering results using this cell are presented, and potential applications are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1145148
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  • 5
    Digitale Medien
    Digitale Medien
    Time domain operation of the TRAPATT diode for picosecond-kilovolt pulse generation (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3286-3288 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Operation of the trapped plasma avalanche transit time (TRAPATT) diode in the time domain is presented. When operated in the time domain, pulses with amplitudes greater than 1,000 V and risetimes well under 300 ps can be achieved. Selection of a diode for use as a TRAPATT diode is discussed. Experimental results demonstrate pulse generation with an amplitude of 2000 V into 50 Ω and a risetime of 200 ps using a single diode and a power MOSFET driving circuit.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1144565
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  • 6
    Digitale Medien
    Digitale Medien
    Series operation of power MOSFETs for high-speed, high-voltage switching applications (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 1655-1656 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Series operation of power metal-oxide semiconductor field-effect transistors (MOSFETs) to increase their effective hold off voltage is described. The design procedure presented is a modification of a recently reported [Baker and Johnson, Rev. Sci. Instrum. 63, 5799 (1992)] method. Comments are made on implementing MOSFET stacks in various types of instrumentation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1144043
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  • 7
    Digitale Medien
    Digitale Medien
    Column III vacancy- and impurity-induced layer disordering of AlxGa1−xAs-GaAs heterostructures with SiO2 or Si3N4 diffusion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6813-6818 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Experiments are described determining the critical parameters for vacancy- and impurity-induced layer disordering of AlxGa1−xAs-GaAs quantum-well heterostructure (QWH) crystals that utilize SiO2 and Si3N4 diffusion source layers. The SiO2- or Si3N4-capped QWH crystal surface reaches equilibrium with the external annealing ambient by diffusion of Ga and As through the encapsulant layer, thus determining the crystal-surface deviation from stoichiometry and the column III vacancy concentration for layer disordering. By proper design of the QWH crystal, encapsulant layer thickness, and annealing ambient, the SiO2 (Si3N4) can be employed as a column III vacancy source (or mask) or as a Si and O (or N) diffusion source to effect impurity-induced layer disordering.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345070
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  • 8
    Digitale Medien
    Digitale Medien
    Generation of high-energy x-radiation using a plasma flow switch (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1999-2007 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Experiments with coaxial plasma guns at currents in excess of ten megamperes have resulted in the production of high-voltage pulses (0.5 MV) and hard x radiation (10–200 keV). The x-radiation pulse occurs substantially after the high-voltage pulse suggesting that high-energy electrons are generated by dynamic processes in a very high speed ((approximately-greater-than)106 m/s), magnetized plasma flow. Such flows, which result from acceleration of relatively low-density plasma (10−4 vs 1.0 kg/m3) by magnetic fields of 20–30 T, support high voltages by the back electromotive force-u×B during the opening switch phase of the plasma flow switch. A simple model of classical ion slowing down and subsequent heating of background electrons can explain spectral evidence of 30-keV electron temperatures in fully stripped aluminum plasma formed from plasma flows of 1–2 × 106 m/s. Similar modeling and spectral evidence indicates tungsten ion kinetic energies of 4.5 MeV and 46 keV electron temperatures of a highly stripped tungsten plasma.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.348773
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  • 9
    Digitale Medien
    Digitale Medien
    Si impurity-induced layer disordering of Alx Ga1−x -GaAs quantum-well heterostructures by As-free open-tube rapid thermal annealing (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6199-6206 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Data are presented describing Si impurity-induced layer disordering (IILD) and Al-Ga interdiffusion in AlxGa1−x As-GaAs quantum-well heterostructures (QWHs) using open-tube rapid thermal annealing (900–1000 °C) in a flowing N2/H2 ambient. The data show that Al-Ga interdiffusion is enhanced by n-type crystal doping and suppressed by p-type doping. By surrounding the active layers of the heterostructure with layers of opposite doping, we show that the surrounding layers modify the interdiffusion by controlling the diffusion of point defects to the active layers of the heterostructure. Data are presented showing the effects of dielectric encapsulation (SiO2, Si3N4 ) on Al-Ga interdiffusion. The data show that regardless of doping SiO2 enhances interdiffusion as compared to Si3N4. To achieve more thorough layer intermixing of AlxGa1−x As-GaAs QWHs, Si IILD is also investigated in the high-temperature As-poor regime. The experimental data show that in a high-temperature As-poor annealing ambient, little or no Si diffusion occurs from an elemental Si source in contact with a p-type GaAs QWH cap layer. To achieve Si diffusion under these conditions requires removal of the GaAs cap and the use of Al-reduced SiO2 or Si3N4 as a Si diffusion source. Based on secondary-ion mass spectroscopic measurements, direct comparison of Si diffusion from closed-tube (825 °C, 48 h) and open tube (1000 °C, 10 min) anneals shows increased Si incorporation and layer disordering at higher temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.346911
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  • 10
    Digitale Medien
    Digitale Medien
    Effects of low-temperature annealing on the native oxide of AlxGa1−xAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3880-3885 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Data are presented on the effects of low-temperature (∼540 °C) annealing, with and without an As overpressure, on the native oxide of AlxGa1−xAs formed via water vapor oxidation at elevated temperature (∼425 °C). Auger electron spectroscopy data show the Al to be oxidized while the Ga remains unoxidized after the water vapor oxidation of AlxGa1−xAs. Transmission electron microscopy data show a possible composition or phase change upon annealing with an As overpressure. Electron diffraction data indicate that the as-oxidized AlxGa1−xAs is a combination of four possible phases of Al2O3, η, γ, δ, χ, or AlO(OH). Supporting secondary-ion mass spectrometry data are also presented. Ellipsometer measurements indicate an index of refraction n=1.63 (λ=6328 A(ring)) for the native oxide. Ellipsometer measurements of the oxidized and annealed samples show the creation of a region 300–550 A(ring) thick at the oxide-semiconductor interface with n=2.78–2.93.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354482
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