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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport properties of three p-type modulation-doped InxGa1−xAs/InP (0.73≤x≤0.82) single-quantum-well structures grown by metalorganic chemical-vapor deposition are reported. High carrier mobilities of μH=7800 cm2/V s coupled with total carrier concentrations of pS=2.1×1012 cm−2 were reached, for example, for x=0.73 at 5 K. Shubnikov–de Haas and quantum Hall-effect measurements at 50 mK showed the population of two spin-split V3/2 subbands. Using p-modulation-doped field-effect transistors with a gate length of LG=1 μm, fabricated on the same samples, the carrier transport at moderate and high fields was investigated at 77 K. Thereby, the population of the heavy-hole subband and, above a critical field, also the occupation of the light-hole subband were verified. With the help of dc transconductance (gmext-VGS) and magnetotransconductance measurements a decoupling between both subbands at cryogenic conditions and moderate fields was observed, resulting in two clearly defined conducting channels. Further analysis of the measured mobility-voltage (μ-VGS) and velocity-field (vavg-Eavg) profiles revealed that carrier transport in compressively strained two-dimensional hole gas (2DHG) systems is strongly affected by intersubband scattering and shows a nonlinear behavior at low fields, caused by the zone-center degeneracy of their E-k(parallel) distribution.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 8077-8079 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on experimental results with three-terminal superconductor/semiconductor hybrid junctions, which are based on the two-dimensional electron gas at the surface of p-type InAs. A short distance ((approximate)150 nm) between superconducting Nb contacts is obtained using a step geometry. The step geometry allows the realization of different heterostructure potential profiles along the two-dimensional channel. The critical current of the step junctions can be controlled by applying a voltage to highly doped (δ-doped) layers embedded in the heterostructure. With p-δ-doped layers, a p-n junction is introduced in the two-dimensional channel and an asymmetric change of the critical current with respect to the gate voltage or gate current is observed. With n-δ-doped layers, the change is symmetrical. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 106 (1997), S. 321-326 
    ISSN: 1573-7357
    Keywords: 74.50.+r ; 73.25.+i ; 73.40.Sx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Experimental results for novel superconductor/semiconductor hybrid systems are presented. The junctions have a step-like geometry, employing two Nb electrodes which are evaporated onto a step that is etched in InAs. Such a geometry allows one to fabricate short weak links (approximately 200nm) as well as to realize a variety of heterostructure potential profiles along the channel between the superconducting electrodes, since this channel is oriented parallel to the growth direction of the heterostructure. Different semiconductor heterostructures, such as low p-doped InAs, whose native surface inversion layer has the character of a two-dimensional electron gas (2DEG), or npn-InAs heterostructures, where th 2DEG of a thin (150nm) p-layer is sandwiched between two n-InAs layers, are used. By measuring the currentvoltage characteristics at 4.2K, supercurrents, subharmonic gap structures, as well as excess currents, are observed.
    Type of Medium: Electronic Resource
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