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  • 1
    Electronic Resource
    Electronic Resource
    A compact electron beam evaporator for carbon doping in solid source molecular beam epitaxy (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3435-3438 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new type of carbon source using the electron evaporator principle to generate a molecular beam is presented. The electrons are extracted from a hot tungsten filament which is biased negatively up to 1500 V versus the carbon target (ground potential), made from ultrapure pyrolytic graphite. The emission current at a fixed high voltage is controlled via a feedback loop and used to tune the carbon flux. In this way, a flux reproducibility of ±5% is achieved over a working period of 5 months. Flux rates up to 6.1×1011 cm−2 s−1 at a source–sample distance of 250 mm have been achieved. The source design is very compact so it was possible to build it onto a flange with a inner diameter of 40 mm (CF40 flange) which saves mounting space. Using this source it was possible to prepare two dimensional hole gases with hole mobilities up to 160 000 cm2 V−1 s−1 at 1 K. No memory effect was observed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149933
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  • 2
    Electronic Resource
    Electronic Resource
    Low-temperature transport characteristics of AlGaAs-GaAs in-plane-gated wires (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3022-3028 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport characteristics of in-plane-gated wires, in which the conducting two-dimensional electron gas (2DEG) channel and the 2DEG gates are separated by focused Ga-ion-beam scanned lines, are studied at low temperature (1.5 K). They are understood as a combination of the normal field-effect-transistor (FET) characteristics and a peculiar resistance jump at the channel pinch-off threshold. In the normal FET region, the depletion region spreading is gradually controlled by a gate voltage applied to the in-plane gates. The channel conductance variation by the gate voltage is explained by the change of the effective channel width rather than by the change of the carrier density. The variable range of the effective wire width is equal to or less than 0.6 μm in the experiments. In spite of this small controllable value, the channel can be pinched off up to W=10 μm with a gate leakage current of less than 1 nA. The pinch off of the wide wires always occurs together with a resistance jump at the threshold. These characteristics are explained by the drastic extension of the depletion region for the case that a small gate leakage occurs through the AlGaAs (Si) layer but not through the two-dimensional electron gas at the heterointerface. This resistance jump produces an interesting negative drain conductance (drain current/drain voltage) in the drain-voltage–drain-current characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351511
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  • 3
    Electronic Resource
    Electronic Resource
    Lateral spreading of focused ion-beam-induced damage (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1858-1863 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the lateral spreading of implantation-induced damage and measure the position dependence of the cathodoluminescence intensity of GaAs/AlAs heterostructures patterned by a focused Ga+ ion beam. Two luminescence lines, one from a buried AlGaAs/GaAs quantum well and the other from a deeper lying AlAs/GaAs short period superlattice are detected. Implantation doses in the range 1012–1015 cm−2 are investigated. We find that the lateral spreading of implantation induced damage considerably exceeds the implanted region in the case of the quantum well (50 nm below the surface), but is well limited to the implanted region in the case of the superlattice (250 nm below the surface). Micro-Raman measurements allow us to locally probe the degree of crystallinity at a certain point of the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351658
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  • 4
    Electronic Resource
    Electronic Resource
    Intrinsic and extrinsic capacitances of in-plane-gated transistors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8087-8090 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intrinsic and extrinsic capacitances of in-plane-gated (IPG) transistors are calculated by conformal mapping. The capacitance per unit length between coplanar areas is only weakly dependent on the separation. It is essentially determined by the dielectric constant only and has a value of ∼18 pF/m in air. In both ion-implanted and trench-etched IPG transistors the geometry is of minor importance for the low- and high-frequency behavior. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362364
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  • 5
    Electronic Resource
    Electronic Resource
    Deep level transient spectroscopy on focused ion beam written in-plane capacitances (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6088-6093 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss defects created by focused Ga ion beam implantation in GaAs or AlGaAs/GaAs heterostructures using deep level transient spectroscopy (DLTS). A novel contact configuration which is sensitive to defects located at the boundary between implanted and unperturbed regions at a well-defined depth is presented. The DLTS spectra for these samples are dominated by a peak with an activation energy of Ea=0.38 eV. The results show that this peak is associated with implantation-induced damage independent of the ion species. The defect is also found in a sample with Schottky contacts on top of a Ga-implanted GaAs layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355193
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  • 6
    Electronic Resource
    Electronic Resource
    Asymmetrical source-drain characteristics in in-plane-gated transistors written by focused ion beam (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6710-6714 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We observe electrically asymmetrical source-drain characteristics in in-plane-gated transistors with shaped channels, and investigate them for different geometries. We give a qualitative explanation of the asymmetry, which is supported by voltage contrast scanning electron micrographs and the measured interaction between two neighboring channels. These shaped channels show a much higher dc voltage gain than conventional in-plane-gated transistors. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359085
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  • 7
    Electronic Resource
    Electronic Resource
    Increased thermal budget for selectively doped heterostructures by employing AlAs/GaAs superlattices (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 377-379 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The degradation of selectivity doped Al0.35Ga0.65As/GaAs heterostructures caused by rapid thermal annealing (RTA) was studied. The samples were annealed for 30 s at temperatures between 600 °C and 850 °C. Thereafter, the samples were characterized by Hall measurements at room temperature. Conventional heterostructures with a random alloy Al0.35Ga0.65As spacer and donor layer show a strong degradation for annealing temperatures of 650 °C or higher. For heterostructures employing a stoichiometric equivalent short period superlattice (SPS) in spacer and donor region only a slight degradation was found for annealing temperatures up to 850 °C. As reason for the increased thermal stability, the suppression of As loss during the annealing by the SPS was identified. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1386618
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  • 8
    Electronic Resource
    Electronic Resource
    Vanishing contact resistance on polycrystalline YBa2Cu3O7−x (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1017-1019 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The preparation and characterization of gold contacts on polycrystalline YBa2Cu3O7−x ceramics that carry high currents and exhibit contact resistances of only 50 mΩ at room temperature are reported. By cooling the sample this resistance remains essentially constant until the superconducting transition temperature, Tc(approximately-equal-to)89 K, is reached. At Tc the contact resistance decreases like the resistivity of YBa2Cu3O7−x, reaching at T〈Tc about 10 μΩ. This value is comparable to the intrinsic resistance of the contact material. Thus, below Tc, the contacts exhibit vanishing contact resistance at the metal–high-Tc-superconductor interface. Such low contact resistances may be extremely important for the technical application of the novel superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99231
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  • 9
    Electronic Resource
    Electronic Resource
    Superconducting contacts on YBa2Cu3O7−x in magnetic fields (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1216-1218 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The contact resistance Rc of pressed and diffused gold contacts on polycrystalline YBa2Cu3O7−x is known to vanish below the critical temperature Tc≈90 K. The lack of a voltage drop over the contacts at finite currents strongly suggests pair tunneling between the high Tc superconductor and the adjacent gold layer, becoming superconducting via the proximity effect. Comparison of the current-voltage characteristics with those calculated including a Josephson current reveals a point contact structure rather than a homogeneous contact area. The contacts are studied at high currents up to I=19 A at different temperatures and magnetic fields. Staying superconducting at externally applied magnetic fields B up to B=30 mT, Rc rises monotonically with increasing magnetic field to Rc=180 μΩ at B=100 mT. This very low contact resistance persists essentially up to B=10 T, opening the possibility to design high magnetic field devices with negligible contact power dissipation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100669
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  • 10
    Electronic Resource
    Electronic Resource
    High frequency characteristics of in-plane-gate transistors (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1324-1325 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Directly written in-plane-gate (IPG) field effect transistors fabricated using focused ion beams have been proposed and measurements of their dc characteristics have been made. Here, we present for the first time ac measurements up to high frequencies on these transistors. The measurements are made using a direct wafer probing technique. While parasitic elements adversely affect the high frequency operation of the current generation of the IPG transistor, promising results have been obtained. We measure a transconductance of 20 μS which is essentially independent of frequency up to 1 GHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107580
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