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  • 1
    Electronic Resource
    Electronic Resource
    Transmission electron microscopy study of defects in Sn-doped GaAs films grown by molecular beam epitaxy (1987)
    Springer
    Applied physics 44 (1987), S. 143-151 
    Details
    ISSN: 1432-0630
    Keywords: 68.55Jh ; 81.30Fb ; 68.35
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Films of GaAs, heavily doped with Sn, which have been grown by molecular-beam epitaxy are found to contain single-crystal Sn particles situated in the nearsurface region of the epilayer GaAs. The morphology and chemical composition of the particles have been examined by using cross-section transmission electron microscopy combined with energy-dispersive x-ray spectroscopy. Different growth conditions were used to study the Sn-particle formation and high-resolution transmission electron microscopy was used to investigate microstructures. The observations are discussed in terms of several models previously proposed for these phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00626415
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  • 2
    Electronic Resource
    Electronic Resource
    Surface recombination current and emitter compositional grading in Npn and Pnp GaAs/AlxGa1−xAs heterojunction bipolar transistors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 641-643 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimental study of current gain in Npn and Pnp GaAs/AlxGa1−xAs heterojunction bipolar transistors (HBTs) with either compositionally graded or abrupt base-emitter heterojunctions is reported. In both Npn and Pnp device structures, linear compositional grading increases the amount of base current and lowers the transistor current gain from that observed in devices with abrupt base-emitter heterojunctions. Analysis of the dependence of the base current on emitter mesa size indicates that surface recombination dominates the Npn and Pnp base current in both the abrupt and graded devices. Taken together, these results suggest that the magnitude of the surface recombination current in Npn and Pnp GaAs/AlxGa1−xAs HBTs depends not only on the surface recombination velocity of the GaAs base free surface, but also on the energy barrier presented by the emitter to minority carriers attempting to enter the surface channel at the emitter mesa surface. Linear compositional grading of the emitter results in a lowering of this barrier and an increase in base current associated with carrier injection to the transistor surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100904
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  • 3
    Electronic Resource
    Electronic Resource
    Growth and diffusion of abrupt zinc profiles in gallium arsenide and heterojunction bipolar transistor structures grown by organometallic vapor phase epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 4485-4493 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth and diffusion of abrupt Zn profiles in undoped gallium arsenide (GaAs), silicon-doped GaAs, and heterojunction bipolar transistor structures grown by organometallic vapor phase epitaxy have been studied using secondary ion mass spectrometry depth profiling. The depth profiles indicate that abrupt (within 100 A(ring)) turn-on of Zn doping to levels approaching 1020 cm−3 are obtainable, while abrupt turn-off is limited to about two orders of magnitude due to dopant tailing toward the surface resulting from residual Zn in the reactor. The sharp diffusion fronts resulting from post-growth anneals indicate that the Zn diffusion coefficient has a concentration dependence. However, the diffusion of Zn at high concentrations appears to be inhibited by crystal defect kinetics resulting in a relatively concentration-independent Zn diffusion coefficient. The V/III growth ratio did not have an effect on Zn diffusion in undoped or silicon-doped GaAs. The diffusion of Zn in heterojunction bipolar transistor structures differs in that the diffusion of Zn into the GaAs collector is larger by an order of magnitude and decreases with an increase in V/III growth ratio. In addition, the diffusion of Zn into the aluminum gallium arsenide (AlGaAs) emitter is significantly lower and more effectively inhibited by an increase in V/III ratio than the diffusion of Zn into the GaAs collector.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340143
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of compositionally graded to abrupt emitter-base junctions used in the heterojunction bipolar transistor (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2663-2669 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes an experimental study which compares compositionally graded to abrupt emitter-base junctions which are used in the heterojunction bipolar transistor (HBT). It is found that the larger current gains are obtained in devices with abrupt emitter-base junctions. Measurements of electroluminescence emitted from the base region and temperature-dependent current gain indicate that the larger current gain in the abrupt devices is due to a larger base-transport factor. The data presented provide evidence that the injection of hot electrons from an abrupt emitter-base junction is realizable and can result in improved performance of the HBT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337897
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  • 5
    Electronic Resource
    Electronic Resource
    Lattice-strained heterojunction InGaAs/GaAs bipolar structures: Recombination properties and device performance (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1234-1236 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Double-heterojunction NpN GaAs/InxGa1−xAs/GaAs bipolar transistor layers have been grown by molecular-beam epitaxy, and large-area devices have been processed and characterized. The indium mole fraction in the strained base layer, and thus the band offsets, has been varied with significant differences in current gains. From the gain versus indium-composition relation a valence-band offset of ΔEv =9.7 meV/% In is derived. We found that the highest base-In content yields the highest-gain devices despite the presence of interface misfit dislocations and dark-line defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338179
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  • 6
    Electronic Resource
    Electronic Resource
    Anomalous redistribution of beryllium in GaAs grown by molecular beam epitaxy (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 4130-4134 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The purpose of this study is to investigate anomalous redistribution of beryllium (Be) in GaAs grown by molecular beam epitaxy (MBE). A concentration-dependent diffusion coefficient for Be is found from the substitutional-interstitial diffusion model. The importance of the generation of BeI from Ga point defects (vacancies or interstitials) in the diffusion process is also presented. Extremely rapid interstitial diffusion during growth, on the order of 30 μm in 1 h at 680 °C, has also been observed. This effect begins to occur for hole concentrations above 1019/cm3. Unintentional incorporation of Be into GaAs grown after closing the Be shutter is also presented. Consideration of the surface concentration of Be during MBE growth facilitates the explanation of this memory effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335543
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization and thermal instability of low-resistivity carbon doped GaAs grown by low-pressure organometallic vapor phase epitaxy (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 704-708 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heavily carbon (C)-doped GaAs grown by low-pressure organometallic vapor phase epitaxy using carbon tetrachloride exhibits a lifetime significantly lower than that obtained by zinc doping in previous work and does not exhibit strain relaxation for thicknesses above twice the critical thickness for misfit dislocation formation (hc). GaAs:C+ is shown to be thermally unstable to annealing cycles as brief as 600 °C for 4 min. The instability is manifest in conductivity, photoluminescence intensity, and lattice contraction reduction for carbon concentrations above 7×1019 cm−3. This reduction is not alleviated by reducing the layer thickness below hc or adding indium to increase hc above the layer thickness. This suggests that either hc is not an adequate measure of misfit dislocation formation during annealing or misfit dislocation generation is in general not responsible for the thermal instability of GaAs:C+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351330
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  • 8
    Electronic Resource
    Electronic Resource
    Observation of radiative and nonradiative tunneling in GaAs/AlxGa1−xAs heterojunction bipolar transistors with compositionally graded base-emitter heterojunctions (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3282-3285 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comparative experimental study of 77-K current gain and electroluminescent (EL) spectra in Npn GaAs/AlxGa1−xAs heterojunction bipolar transistors (HBTs) with either compositionally graded or abrupt base-emitter heterojunctions is reported. Shifting-peak spectra associated with radiative tunneling of carriers into the base-emitter heterojunction space-charge region are observed to dominate the 77-K EL spectra of HBTs with linearly graded emitters. The 77-K EL spectra of the abrupt HBTs are characterized by a peak whose energy position is invariant with respect to base-emitter bias and corresponds to recombination of electrons diffusing across the HBT base. Comparison of EL peak intensity and transistor base current indicates that the graded HBT current gain at 77 K is determined by nonradiative tunneling of electrons and holes to deep levels at the base-emitter junction. The loss of minority carriers to radiative and nonradiative tunneling current mechanisms in the graded HBT causes the 77-K current gain of the graded HBT to be significantly lower than that of the abrupt HBT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342687
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  • 9
    Electronic Resource
    Electronic Resource
    p-type doping limit of carbon in organometallic vapor phase epitaxial growth of GaAs using carbon tetrachloride (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2348-2350 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The doping limit of carbon in GaAs grown by organometallic vapor phase epitaxy (OMVPE) using carbon tetrachloride (CCl4) as a p-type dopant source has been investigated by variation of the V/III ratio, growth temperature, and CCl4 flow rate. Lower V/III ratios, lower growth temperatures, and higher CCl4 flow rates generally yielded higher hole concentrations. Hole concentrations as high as 1020 cm−3 were achieved. Attempts to achieve higher hole concentrations via higher CCl4 flow rates were limited by inhibition of growth and morphology degradation. Majority-carrier hole mobilities of carbon-doped GaAs were more than 50% greater than that of zinc-doped GaAs for comparable hole concentrations obtained in previous work. Nonalloyed contacts to this material resulted in contact resistivities of 4×10−7 Ω cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103889
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