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  • 2005-2009  (1)
  • 2000-2004  (11)
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  • 1
    Electronic Resource
    Electronic Resource
    Mechanisms for Si dopant migration in molecular beam epitaxy AlxGa1−xAs (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4056-4060 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Because of well-known surface segregation effects in molecular beam epitaxy growth, Si dopant atoms deposited as thin layers in AlxGa1−xAs typically become distributed over many atomic layers. We have measured the Si depth distributions in (100) and (311)A samples grown at temperatures between 420 and 655 °C, with Al fraction x=0, 0.1, and 0.32. The surface migration decay length Λ for a Si atom on a growing (100) surface is strongly temperature dependent but nearly independent of x, with Λ(approximate)8 nm at 655 °C. The x=0(100) measurements show evidence for a minimum value Λ(approximate)0.6 nm at low temperatures and a maximum value Λ(approximate)8.5 nm at high temperatures. The data are in accord with a thermally activated surface segregation process with activation energy (1.8±0.4) eV acting in parallel with a temperature independent surface segregation mechanism. The (311)A surface shows Λ=(3.3±0.1) nm virtually independent of temperature for x=0. The Si decay length for the (311)A surface strongly increases with x, and for x=0.32 there is no significant difference in Λ for the (100) and (311)A surfaces. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1308073
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  • 2
    Electronic Resource
    Electronic Resource
    Inhomogeneous spatial distribution of reverse bias leakage in GaN Schottky diodes (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1685-1687 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The reverse bias leakage current in macroscopic GaN Schottky diodes is found to be insensitive to barrier height. Using a scanning current–voltage microscope, we show that the reverse bias current occurs at small isolated regions, while most of the sample is insulating. By comparing the current maps to topographic images and transmission electron microscopy results, we conclude that reverse bias leakage occurs primarily at dislocations with a screw component. Furthermore, for a fixed dislocation density, the V/III ratio during the molecular beam epitaxial growth strongly affects reverse leakage, indicating complex dislocation electrical behavior that is sensitive to the local structural and/or chemical changes. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1356450
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  • 3
    Electronic Resource
    Electronic Resource
    High-mobility AlGaN/GaN heterostructures grown by molecular-beam epitaxy on GaN templates prepared by hydride vapor phase epitaxy (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2888-2890 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the growth and transport properties of high-mobility two-dimensional electron gases (2DEGs) confined at the AlGaN/GaN interface grown by plasma-assisted molecular-beam epitaxy on GaN templates prepared by hydride vapor phase epitaxy. We have grown samples over a broad range of electron densities ranging from ns=6.9×1011 to 1.1×1013 cm−2, and at T=4.2 K, observe a peak mobility of 53 300 cm2/V s at a density of 2.8×1012 cm−2. Magnetotransport studies on these samples display exceptionally clean signatures of the quantum Hall effect. Our investigation of the dependence of 2DEG mobility on carrier concentration suggests that the low-temperature mobility in our AlGaN/GaN heterostructures is currently limited by the interplay between charged dislocation scattering and interface roughness. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1323856
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  • 4
    Electronic Resource
    Electronic Resource
    Ballistic cooling in a wideband two-dimensional electron gas bolometric mixer (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 1243-1245 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that bolometric mixers fabricated from a high mobility two-dimensional electron gas can reach a regime where electron energy relaxation is dominated by ballistic, rather than diffusive, outflow of excited electrons. This ballistic cooling mechanism establishes the maximum physical limit on mixer speed for a transit-time limited device. Intermediate frequency bandwidths of nearly 40 GHz have been obtained in devices with channel lengths 〉1 μm in ballistically cooled devices. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1500429
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of chirp in diffraction of short electromagnetic pulses through subwavelength apertures (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1319-1321 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Short electromagnetic pulses experience significant spectral and temporal deformation when diffracted on subwavelength apertures. Temporal delay/advancement is one of the effects that occurs when a pulse passes through the aperture. In this study, it is demonstrated that the intrinsic negative chirp of terahertz pulses is the origin of the temporal advancement in the limit that the aperture is much smaller than the wavelength of the pulse. The advancement is shown to disappear for unchirped terahertz pulses. The chirp effect is general for any system where the diffracted or scattered field is wavelength dependent. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1452786
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  • 6
    Electronic Resource
    Electronic Resource
    Terahertz pulse propagation through small apertures (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 907-909 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission of single-cycle terahertz pulses through subwavelength apertures is experimentally studied in the near-field zone. Measurements of throughput for aperture sizes d as small as λ/300 show that the theoretical d3 law requires a correction term which takes into account the physical thickness of the aperture screen. Frequency dependent transmission of the broad band pulses explains changes in their spectral and temporal characteristics. Practical application of small apertures in near-field microscope probes allows achievement of spatial resolution of 7 μm for pulses with a broad spectral content of λ=120–1500 μm. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1392303
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  • 7
    Electronic Resource
    Electronic Resource
    Wide bandwidth millimeter wave mixer using a diffusion cooled two-dimensional electron gas (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2888-2890 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Very fast millimeter wave mixers have been fabricated from a high mobility two-dimensional electron gas (2DEG) in a GaAs–AlGaAs heterostructure. Using a 115 GHz local oscillator, intermediate frequency (IF) bandwidths exceeding 20 GHz have been obtained for channel lengths L of a few microns. Operating at 77 K, the IF bandwidth scales as L−2, indicating that the response speed is determined by the diffusion transit time of hot electrons to the leads. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1370982
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  • 8
    Electronic Resource
    Electronic Resource
    Fabrication of extremely narrow metal wires (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1991-1993 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A robust technique for fabrication of metal wires with controlled widths substantially below 10 nm is presented. By etching a cleaved molecular-beam epitaxy grown substrate, a mechanical template is produced with surface relief of atomic lateral definition. Using metal deposition and directional ion etching of such a substrate, electrically continuous wires are formed from AuPd alloy with diameters as small as 3 nm and lengths greater than 1 μm. This technique can be used with a variety of materials and makes metallic nanostructures on a previously inaccessible size scale. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1312256
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  • 9
    Electronic Resource
    Electronic Resource
    Four-terminal resistance of a ballistic quantum wire (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 411 (2001), S. 51-54 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The electrical resistance of a conductor is intimately related to the relaxation of the momentum of charge carriers. In a simple model, the accelerating force exerted on electrons by an applied electric field is balanced by a frictional force arising from their frequent collisions with ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35075009
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  • 10
    Electronic Resource
    Electronic Resource
    Imaging of localized electronic states in the quantum Hall regime (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 404 (2000), S. 473-476 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The concept of electron localization has long been accepted to be essential to the physics of the quantum Hall effect in a two-dimensional electron gas. The exact quantization of the Hall resistance and the zero of the diagonal resistance over a range of filling factors close to integral ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35006591
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