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  • 1
    Electronic Resource
    Electronic Resource
    Structural properties of As-rich GaAs grown by molecular beam epitaxy at low temperatures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1881-1883 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs layers grown by molecular beam epitaxy (MBE) at substrate temperatures between 200 and 300 °C were studied using transmission electron microscopy (TEM), x-ray diffraction, and electron paramagnetic resonance (EPR) techniques. High-resolution TEM cross-sectional images showed a high degree of crystalline perfection of these layers. For a layer grown at 200 °C and unannealed, x-ray diffraction revealed a 0.1% increase in the lattice parameter in comparison with bulk GaAs. For the same layer, EPR detected arsenic antisite defects with a concentration as high as 5×1018 cm−3. This is the first observation of antisite defects in MBE-grown GaAs. These results are related to off-stoichiometric, strongly As-rich growth, possible only at such low temperatures. These findings are of relevance to the specific electrical properties of low-temperature MBE-grown GaAs layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101229
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of substrate misorientation and background impurities on electron transport in molecular-beam-epitaxial-grown GaAs/AlGaAs modulation-doped quantum-well structures (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 954-960 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single GaAs quantum wells, clad with Al0.3Ga0.7As, and modulation doped with silicon introduced in the Al0.3Ga0.7As after the quantum wells are grown have been grown by molecular-beam epitaxy on GaAs substrates tilted a few degrees from the nominal (001) plane towards either of the (111) planes. The low-field two-dimensional electron gas mobility is observed to be a function of the tilt angle (0°, 2°, 4°, 6.5°) and of the direction of tilt [towards (111)A or (111)B]. The two-dimensional electron gas mobilities in quantum-well structures grown on substrates tilted towards (111)A are larger than those in structures grown on nominally flat (001) substrates. The improvement in two-dimensional electron gas transport is attributed to an improvement in the quality of the inverted interface (i.e., GaAs grown on AlGaAs). Quantum wells grown on substrates tilted toward (111)A also exhibit larger two-dimensional electron gas mobilities than quantum wells grown on substrates tilted toward (111)B for a given angle of tilt. For quantum-well structures where interface scattering from the inverted interface is significant, the two-dimensional electron gas mobility is observed to be anisotropic and larger in the [110] direction in comparison to the [1¯10] direction. The anisotropy in electron transport in the GaAs quantum well is observed to be larger for structures where the substrate tilt is towards (111)B in comparison to (111)A. For quantum wells grown on substrates tilted toward (111)A the anisotropy in two-dimensional electron gas mobility gets progressively larger as the tilt angle gets smaller. Larger molecular-beam epitaxy machine background impurity concentrations are observed to significantly increase the magnitude of the anisotropy in two-dimensional electron gas mobility suggesting that impurities and/or defects introduced during MBE growth are the origin of the anisotropic transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339707
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  • 3
    Electronic Resource
    Electronic Resource
    Anisotropic transport in modulation-doped quantum-well structures (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2301-2306 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Anisotropic electron transport has been observed in GaAs modulation-doped quantum wells grown by molecular-beam epitaxy on a thick (001) Al0.3Ga0.7As buffer grown at 620 °C. The low-field electron mobility at 77 K in the [110] direction is a factor of 2 larger than the mobility in the [1¯10] direction for a 90-A(ring) quantum well. Thicker quantum wells (150, 200, and 300 A(ring)) show progressively less anisotropy, which vanishes for a 300-A(ring) quantum well. The degree of anisotropy is also reduced or eliminated by suspending growth of the Al0.3Ga0.7As for a period of 300 s prior to growing the GaAs quantum well. Growing the Al0.3Ga0.7As buffer at higher temperatures (680 °C) also reduces the degree of anisotropy. Higher two-dimensional electron gas sheet densities result in less anisotropy. The anisotropy is eliminated by replacing the thick Al0.3Ga0.7As buffer with a periodic multilayer structure comprising 15 A(ring) of GaAs and 200 A(ring) of Al0.3Ga0.7As. The degree of anisotropy is related to the thickness and growth parameters of the Al0.3Ga0.7As layer grown just prior to the growth of the GaAs quantum well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337940
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of substrate misorientation on defect and impurity incorporation in GaAs/AlGaAs heterostructures grown by molecular-beam epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5115-5120 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs/AlGaAs heterostructures have been grown by molecular-beam epitaxy on GaAs substrates intentionally oriented (tilted) a few degrees (0–6.5) off the (001) plane towards either (111)A, (111)B, or (011). We observe that the 4-K photoluminescence and low-field electron transport properties of these structures may be functions of the substrate tilt angle and tilt direction depending on the concentration of impurities incorporated during growth. A substrate tilt during molecular-beam epitaxy is observed to have the largest effect on these properties when the background impurity concentration in the molecular-beam epitaxial machine is high. This supports our contention that the observed changes in material characteristics are due to differences in the incorporation of defects and impurities. The incorporation of defects and impurities are reduced by using substrates tilted toward (111)A in comparison to nominally flat (001) substrates or substrates tilted toward (111)B.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340412
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of an intentional substrate misorientation on deep electron traps in AlGaAs grown by molecular beam epitaxy (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 2248-2250 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep level transient capacitance spectroscopy has been used to investigate deep level electron traps in thick silicon-doped AlGaAs grown by molecular beam epitaxy (MBE) on GaAs substrates intentionally misoriented (tilted) a few degrees from a nominally (001) surface. Of the three dominant traps observed in AlGaAs, the concentrations of two of these are observed to be a direct function of the substrate tilt angle and tilt direction. The concentration of the third dominant trap, which is related to the DX center, is independent of substrate misorientation during MBE. These observations will help in identifying which impurities and/or defects are affected by substrate misorientation during MBE growth in addition to identifying the origin of deep levels in AlGaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98926
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of excess gallium vacancies in low-temperature GaAs/AlAs/GaAs:Si heterostructures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 156-160 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article shows that the presence of low-temperature-grown GaAs (LT-GaAs) in LT-GaAs/AlAs/GaAs:Si heterostructures increases the Al/Ga interdiffusion at the heterostructure interfaces. The interdiffusion enhancement is attributed to the presence of Ga vacancies (VGa) in the As-rich LT-GaAs, which diffuses from a supersaturation of VGa frozen-in during sample growth. Chemical mapping, which distinguishes between the AlAs and GaAs lattices at an atomic scale, is used to measure the Al concentration gradient in adjacent GaAs:Si layers. A correlation is observed between the Al/Ga interdiffusion and the gate breakdown voltage in metal-insulator field-effect transistor structures containing LT-GaAs. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362742
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  • 7
    Electronic Resource
    Electronic Resource
    Picosecond GaAs-based photoconductive optoelectronic detectors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 890-892 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel material deposited by molecular beam epitaxy at low substrate temperatures using Ga and As4 beam fluxes has been used as the active layer for a high-speed photoconductive optoelectronic switch. The high-speed photoconductive performance of the material was assessed by fabricating two devices: an Auston switch and a photoconductive-gap switch with a coplanar transmission line. In a coplanar transmission line configuration, the speed of response is 1.6 ps (full width at half maximum) and the response is 10 to 100 times greater than that of conventional photoconductive switches. Since the material is compatible with GaAs discrete device and integrated circuit technologies, this photoconductive switch may find extensive applications for high-speed device and circuit testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100800
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  • 8
    Electronic Resource
    Electronic Resource
    Spectroscopic studies of the influence of intentionally increased CO partial pressure on the incorporation of residual C impurities in molecular beam epitaxy GaAs (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2438-2440 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-purity Si-doped molecular beam epitaxy (MBE) GaAs layers grown with and without the intentional introduction of CO gas have been characterized by Hall effect measurements, photoluminescence, and photothermal ionization spectroscopy. The results indicate that CO itself is not the source of residual C acceptor impurities in MBE GaAs samples. The observations of the correlation of residual C impurity incorporation with the residual CO gas in the MBE growth chamber suggest that the partial pressure of CO, PCO , gives a quantitative indication of background levels of hydrocarbons which are the source of C acceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100410
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  • 9
    Electronic Resource
    Electronic Resource
    Small-signal admittance and switching measurements of the resonant-tunneling diode (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 521-523 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the small-signal admittance and the large-signal switching time of In0.53Ga0.47As/AlAs resonant-tunneling diodes are presented. The small-signal admittance in the positive differential-resistance region is found to be only a weak function of frequency. In contrast, the admittance in the negative differential-resistance region is a strong function of frequency, and the associated time constant is a strong function of bias voltage. It is found that the large-signal switching time is approximately a factor of 10 greater than the small-signal time constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109992
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  • 10
    Electronic Resource
    Electronic Resource
    Resonant tunneling through mixed quasibound states in a triple-well structure (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3016-3018 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A triple-well resonant-tunneling structure made from the In0.53Ga0.47As/AlAs material system yields a broad negative differential resistance (NDR) region without the precipitous drop in current that occurs in single-well structures. This NDR characteristic is attributed to resonant tunneling through mixed quasibound states. A diode made from this structure is used to generate a nearly constant power of 0.5 mW up to 16 GHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109175
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