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  • 1990-1994  (34)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Deposition and surface characterization of high quality single crystal GaN layers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3108-3110 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, using low pressure metalorganic chemical vapor deposition we grew extremely high quality single crystal GaN films over basal plane sapphire substrates. Optimization of the buffer layers and the total film thickness played a key role in determining the electrical, optical, crystalline and surface qualities. In this communication we present the surface characterization results for these high quality GaN layers. Reflection high energy electron diffraction, low energy electron diffraction (LEED), and electron energy loss spectroscopy data are presented for clean GaN surfaces. The cleaning procedure was developed using Auger electron spectroscopy analysis. These electron diffraction data indicate the grown surface to be excellent single crystal GaN with a wurtzite structure. To the best of our knowledge ours is the first reported LEED data for single crystal GaN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352999
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Spontaneous current oscillations in optically pumped semi-insulating InP (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4111-4115 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Current oscillations arising from voltage-controlled negative differential resistivity are observed in optically pumped semi-insulating InP at low temperature. The presence of high-field domains sweeping through the sample are detected using photorefractive four-wave mixing. Direct evidence of the role of defects in these current oscillations is presented using deep-level photodiffractive spectroscopy. A deep hole trap with an energy Ev +85 meV is observed. The current oscillations occur only when this defect level is partially occupied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346251
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of buffer layers on the deposition of high quality single crystal GaN over sapphire substrates (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4700-4702 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently several research groups, including ours, have reported on the deposition of extremely high quality single crystal GaN layers over sapphire substrates. One of the keys to obtaining the high quality was the use of a thin AlN or GaN buffer layer between the sapphire substrate and the grown film. In this communication, we discuss the crystallinity and the influence of the buffer layer in controlling the crystalline, optical, and the electrical properties of the GaN depositions. We also compare the use of GaN and AlN as the buffer layer material. Our results indicate that the buffer layer thickness and the total film thickness are the key factors controlling the electrical, optical, and crystalline properties of the GaN depositions over sapphire substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354069
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Chromatic aberration of three-cylinder electrostatic lenses (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3339-3345 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Accurate calculations of the axial chromatic aberration coefficients of geometrically symmetric three-cylinder tripotential electrostatic lenses are presented for two different center electrode lengths. This is an extension of the first-order properties and the third-order spherical aberration coefficients published by Harting and Read.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142550
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  • 5
    Electronic Resource
    Electronic Resource
    Growth of high optical and electrical quality GaN layers using low-pressure metalorganic chemical vapor deposition (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 526-527 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the low-pressure metalorganic chemical vapor deposition of high quality single-crystal GaN layers over basal plane sapphire substrates. Optimization of growth conditions resulted in material with carrier densities of 1017 /cm3 at room temperature and corresponding mobilities around 350 cm2 /V s. The photoluminescence linewidths improved from 160 meV [full width at half maximum (FWHM)] to 25 meV (FWHM). With improved material quality we were able to observe the polar optical mode and the ionized impurity scattering regimes in the mobility versus temperature data. Good quality Schottky barriers were formed on the as-grown material using a tungsten probe and an alloyed indium contact. Our observations indicate a direct correlation between electrical and optical characteristics of good material and strongly question nitrogen vacancies as the sole explanation for the high carrier densities observed in poor quality GaN growths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104575
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  • 6
    Electronic Resource
    Electronic Resource
    Electroabsorption in II-VI multiple quantum wells (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 334-336 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first study of the room-temperature electroabsorption effects in CdZnTe/ZnTe multiple quantum well structures which exhibit sharp excitonic absorption peaks. The magnitude of the Franz Keldysh and quantum-confined Stark Effects are found to be comparable to those of III-V semiconductors. With optimized structures we expect II-VI semiconductors to be important components for information processing in the visible spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104678
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Cross-section transmission electron microscopy study of carbon-implanted layers in silicon (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 798-800 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used cross-section transmission electron microscopy (XTEM) to study microstructures of carbon-implanted silicon layers after high-temperature annealing. It was found that the threshold dose for extended defect formation was much higher for carbon implantation than for other ion species such as B, P, and O. In 2.4 MeV carbon-implanted layers, no dislocations were formed for doses as high as 2×1016 cm−2 after annealing at 1000 °C for 1 h. The threshold was found to be lower for low-energy implantation (100 keV): at a dose of 2×1016 cm−2, when an amorphous layer was formed, microtwins were formed near the projected range upon annealing. Microprecipitates around 50 A(ring) in size were observed in low-energy carbon-implanted samples and the precipitates appeared to be under strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103424
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  • 8
    Electronic Resource
    Electronic Resource
    High electron mobility GaN/AlxGa1−xN heterostructures grown by low-pressure metalorganic chemical vapor deposition (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2408-2410 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter we report the first observation of enhanced electron mobility in GaN/AlxGa1−xN heterojunctions. These structures were deposited on basal plane sapphire using low-pressure metalorganic chemical vapor deposition. The electron mobility of a single heterojunction composed of 500 A(ring) of Al0.09Ga0.91N deposited onto 0.3 μm of GaN was around 620 cm2/V s at room temperature as compared to 56 cm2/V s for bulk GaN of the same thickness deposited under identical conditions. The mobility for the single heterojunction increased to a value of 1600 cm2/V s at 77 K whereas the mobility of the 0.3 μm GaN layer alone peaked at 62 cm2/V s at 180 K and decreased to 19 cm2/V s at 77 K. A 18-layer multiple heterojunction structure displayed a peak mobility of 1980 cm2/V s at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104886
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  • 9
    Electronic Resource
    Electronic Resource
    Vertical-cavity, room-temperature stimulated emission from photopumped GaN films deposited over sapphire substrates using low-pressure metalorganic chemical vapor deposition (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1515-1517 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first observation of near-UV vertical-cavity stimulated emission from a photopumped GaN epilayer at room temperature. The epilayer was deposited over AIN-coated basal plane sapphire substrate using low-pressure metalorganic chemical vapor deposition. Epitaxy quality of a 1.5-μm-thick GaN layer was high enough to achieve stimulated emission at room temperature. The observed near-UV optical emission power was a nonlinear function of the pump power density. At threshold power density, we also observed line narrowing and a shift of the peak UV emission towards longer wavelengths. Data comparing the UV emission for the vertical-cavity and the edge emission geometry are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105163
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  • 10
    Electronic Resource
    Electronic Resource
    Deep level photodiffractive spectroscopy of semiconductors (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 163-165 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Defect levels in semi-insulating GaAs and InP are investigated by deep level photodiffractive spectroscopy. Temperature-dependent four-wave mixing based both on photochromic and photorefractive effects permits a determination of the energy levels within the semiconductor band gap. This optical technique eliminates difficulties encountered with high-resistivity material using conventional electrical measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103038
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