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  • 1
    Digitale Medien
    Digitale Medien
    Effect of gravity on the deposition of colloidal particles on a planar surface (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 8605-8612 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A steady state convective-diffusion equation is solved using a collocation method to find the concentration profile and flux of adsorbing particles near a particle adsorbed on the plane surface. At small values of the gravity number, NG=πd4Δρ/6kT, the concentration profile and flux vary slowly near the preadsorbed particle, while they are highly nonuniform at large values of NG. The effect of the position of the system boundary on the collocation calculation is discussed and it is shown how the concept of flux balance may be used to improve the accuracy of the results. Finally, we develop two fitting functions at high and low values of NG, respectively. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.480201
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  • 2
    Digitale Medien
    Digitale Medien
    Frequency dependence of the plasma density for helicon plasmas (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1463-1467 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Variations of plasma density are investigated as a function of frequency of rf power in a helicon plasma source. Abrupt, almost step-like changes in the plasma density are observed during the frequency scans under various conditions of the input rf power, the argon gas pressure, and the magnetic field. It is found that the transition frequencies shift to the lower value region as the input rf power and/or the argon gas pressure is increased, and to the higher value region as the magnetic field is increased. The observed density transitions are compared with semianalytical calculations based on the power balance relation and it has been shown that the results are in good agreement. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872325
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  • 3
    Digitale Medien
    Digitale Medien
    Anomalous oxygen annealing effects on La0.7Ca0.3MnO3 films grown on MgO substrates (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 353-355 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Epitaxial La0.7Ca0.3MnO3 thin films were grown on MgO (001) substrates by pulsed laser deposition. The as-grown films exhibit a metal–insulator transition at temperatures ranging from 200 to 230 K. Surprisingly, the transition temperature of postannealed films under O2 at 900 °C decreases by more than 100 K, featured with the colossal magnetoresistance. The O2 annealed films also show thermal hysteresis in resistivity and nonlinear I–V behavior. These results are interpreted in terms of Mn deficiency induced by large structural difference between film and substrate, and also discussed in viewpoint of a percolative phase transition. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1338972
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  • 4
    Digitale Medien
    Digitale Medien
    High-quantum-efficiency 0.5 eV GaInAsSb/GaSb thermophotovoltaic devices (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1305-1307 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report high-performance lattice-matched GaInAsSb/GaSb thermophotovoltaic (TPV) devices with a 0.5 eV band gap. The TPV structures were grown on GaSb substrates by organometallic vapor phase epitaxy at a lower temperature (525 °C compared to 550 °C) to improve the quality of the metastable GaInAsSb alloy. The 0.5 eV TPV devices exhibit external quantum efficiency as high as 60%, which corresponds to an internal quantum efficiency of 90%, assuming 35% reflection losses. This efficiency is comparable to the value measured for 0.53 eV devices. The ratio of the open circuit voltage to band-gap energy ratio decreases from 0.57 for 0.53 eV devices to 0.48 for 0.5 eV devices. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.124676
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  • 5
    Digitale Medien
    Digitale Medien
    High-performance GaInAsSb thermophotovoltaic devices with an AlGaAsSb window (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3758-3760 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A large increase in the quantum efficiency (QE) and open-circuit voltage Voc of GaInAsSb thermophotovoltaic (TPV) devices is obtained by the use of an AlGaAsSb window layer compared with devices without a window layer. The TPV structure, grown on GaSb substrates by organometallic vapor phase epitaxy or molecular beam epitaxy, consists of a 1-μm-thick n-GaInAsSb base layer, a 3-μm-thick p-GaInAsSb emitter layer, a 100-nm-thick AlGaAsSb window layer, and a 25-nm-thick GaSb contacting layer. The band-gap energy of the lattice-matched GaInAsSb is 0.53–0.55 eV. The peak internal QE of the TPV cells with the window is 〉90%, compared with less than 60% for those without the window. At a short-circuit current density of ∼1000 mA/cm2, Voc of ∼300 meV is obtained for cells with the window layer, compared with less than 220 meV without the window layer. These increases are attributed to a substantial decrease in the surface recombination velocity with the window layer. Based on a standard calculation, the electron diffusion length in the p-GaInAsSb layer is at least 5 μm. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.120497
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  • 6
    Digitale Medien
    Digitale Medien
    Thick AlxGa1−xAs: An intrinsically percolating barrier owing to its microscopic structural inhomogeneity (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2513-2515 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A significant charge transfer, which differs from tunneling, over thick AlxGa1−xAs barrier in GaAs/AlxGa1−xAs asymmetric double quantum wells is studied by cw photoluminescence excitation (PLE) and time-resolved photoluminescence. It is found that 300-A(ring)-thick Al0.3Ga0.7As barrier is universally "leaky'' with transport time of ∼300 ps, while AlAs and AlAs/GaAs digital alloy barriers with same thickness are not. Aided by a model calculation, we suggest that the intrinsic inhomogeneities in the alloy, which recent x-ray and scanning tunneling microscope studies revealed, may be responsible. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.117724
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  • 7
    Digitale Medien
    Digitale Medien
    n-AlGaSb and GaSb/AlGaSb double-heterostructure lasers grown by organometallic vapor phase epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 400-402 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: n-type doping of AlxGa1−xSb epilayers (0≤x≤1) grown by organometallic vapor phase epitaxy has been achieved by using tritertiarybutylaluminum, triethylgallium, and trimethylantimony as the organometallic precursors and diethyltellurium as the doping source. Electron concentrations exceed 1017 cm−3 for layers with x〈0.3, and decrease to ∼1016 cm−3 for x=1 as a result of higher residual acceptor concentration. Lattice-mismatched double-heterostructure diode lasers with AlGaSb cladding layers and GaSb active layer are demonstrated, and indicate the potential of OMVPE for growth of GaSb-based materials for electronic and optoelectronic devices. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.116698
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  • 8
    Digitale Medien
    Digitale Medien
    175 K continuous wave operation of InAsSb/InAlAsSb quantum-well diode lasers emitting at 3.5 μm (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2936-2938 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Multiple quantum-well diode lasers incorporating compressively strained InAs0.935Sb0.065 wells and tensile-strained In0.15Al0.85As0.9Sb0.1 barriers are reported. These lasers, grown on InAs substrates by molecular beam epitaxy, have emission wavelengths between 3.2 and 3.55 μm. Broad-stripe lasers have exhibited pulsed threshold current density as low as 30 A/cm2 at 80 K and the characteristic temperatures between 30 and 40 K. The maximum pulsed operating temperature is 225 K. Ridge-waveguide lasers have cw threshold current of 12 mA at 100 K, and the maximum cw operating temperature is 175 K. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.116360
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  • 9
    Digitale Medien
    Digitale Medien
    InAsSb/InAlAsSb strained quantum-well diode lasers emitting at 3.9 μm (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 332-334 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Strained quantum-well diode lasers emitting at 3.9 μm have been fabricated. The laser structure, grown on a GaSb substrate by molecular beam epitaxy, consists of compressively strained InAsSb active layers and tensile-strained InAlAsSb barrier layers, surrounded by AlAsSb cladding layers. Broad-stripe lasers have exhibited pulsed operation up to 165 K, with threshold current density of 78 A/cm2 at 80 K. The characteristic temperature is 30 K up to 120 K. The devices operated cw up to 123 K, and the maximum cw power at 80 K is 30 mW/facet. Ridge-waveguide lasers have operated cw up to 128 K, with cw threshold current at 80 K of 35 mA. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115435
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  • 10
    Digitale Medien
    Digitale Medien
    Ultralow-threshold (50 A/cm2) strained single-quantum-well GaInAsSb/AlGaAsSb lasers emitting at 2.05 μm (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 876-878 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Strained single-quantum-well, broadened-waveguide GaInAsSb/AlGaAsSb diode lasers have exhibited room-temperature threshold current densities as low as 50 A/cm2, one of the lowest values reported for diode lasers at room temperature. These lasers, grown by molecular beam epitaxy, have emission wavelengths of ∼2.05 μm, characteristic temperature of 65 K, internal quantum efficiency of 95%, and internal loss coefficient of 7 cm−1. Single-ended cw power of 1 W is obtained for a 100-μm aperture. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.120922
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