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  • 2000-2004  (105)
  • 1995-1999  (68)
  • 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
    Demonstration of an isolated buried channel field-effect transistor fabricated via in situ patterned electron-beam deposition of Si in GaAs (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6039-6041 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A partial monolayer of silane, SiH4, adsorbed on a GaAs(100) surface at 40 K may be fixed in a desired pattern by irradiation with an electron microbeam, and then covered in situ by GaAs grown by molecular-beam epitaxy. The initial rate of Si coverage under irradiation by 1.5 keV electrons is (0.031±0.005) Si per electron per monolayer of silane. Applications include the in situ fabrication via patterned doping of circuit elements and structures with interesting electronic properties. As an example, we have made an isolated buried channel field-effect transistor and measured its properties. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360542
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements of frequency upconversion and picosecond excitation-correlation luminescence spectra in GaAs quantum wells and determination of time constants describing exciton dynamics (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5921-5931 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the picosecond dynamics of free carriers and excitons in high-quality GaAs quantum wells at 8 K using frequency upconversion (UC) and nonlinear picosecond excitation-correlation (PEC) luminescence spectroscopy under nonresonant excitation conditions with carrier densities of a few 1010 cm−2. We analyze the measurements using a theoretical model of the coupled free electron–hole pair and exciton dynamics, incorporating important density-dependent nonlinear effects, caused by exciton collisions and fermion exclusion. The time-resolved UC photoluminescence (PL) spectra are used to deduce time constants related to free electron–hole (e–h)-pair transformation into excitons and exciton transfer from large K to small K (k is the exciton wave vector). It is shown that unambiguous determination of exciton radiative and nonradiative decay times are possible when both UC and PEC PL spectra are considered simultaneously. We carry out a detailed line-shape analysis of the picosecond UC and PEC PL spectra. We find that while collision broadening is mainly responsible for the observed nonlinear excitonic PEC signal, the PEC PL spectra can be fully explained only when additional nonlinear effects, such as density-dependent radiative lifetime and fermion exclusion, are included in the analysis. From a comparison of the time evolution of both the PEC and UC PL spectra with theory, the time constants introduced in the model to describe free carrier density decay, transfer of excitons with K≠0 to K≈0 states, and their radiative and nonradiative decay are estimated to be about 50, 15, 60, and 1800 ps respectively. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363821
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  • 4
    Electronic Resource
    Electronic Resource
    High mobility GaAs heterostructure field effect transistor for nanofabrication in which dopant-induced disorder is eliminated (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1262-1264 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated field effect transistors with undoped GaAs channels, undoped AlxGa1−xAs barriers, and either n+GaAs or epitaxial Al gates. Low resistance ohmic contacts are made separately to the gate and channel in samples with 250 A(ring) barriers and in which the depth of the channel below the top surface is 900 A(ring). Because electrons in the channel are neutralized by conducting charge on the gate, they do not experience the dopant-induced disorder inevitable in modulation doped structures. Electron mobility is above 106 cm2/V s, even when their Fermi wavelength exceeds 1000 A(ring), making these devices ideally suited for nanofabrication. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114391
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  • 5
    Electronic Resource
    Electronic Resource
    Intersubband emission in double-well structures with quantum interference in absorption (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3477-3479 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intersubband electroluminescence is investigated in structures where two excited states are coupled by tunneling to a common continuum, and exhibit a clear sign of destructive interference in absorption spectroscopy. We show that, in addition to the nonreciprocity between the matrix elements for absorption and emission, the difference between the absorption and emission profiles has its origin also in the electron distribution of the injector. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120364
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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    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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