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  • 11
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1460-1463 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the growth and characterization of a high-quality wide (∼2000 A(ring)) three-dimensional electron gas (3DEG) with periodic density modulation (period ∼200 A(ring)) in a modulation-doped wide parabolic potential well with a superimposed superlattice. Computer-controlled molecular beam epitaxy is used to synthesize the potential well as a graded AlxGa1−xAs digital alloy. The density-modulated 3DEG is compared to a uniform 3DEG of the same average density and width in a parabolic well without the superlattice. The Al mole fraction profiles for the two samples are measured in calibration runs immediately prior to actual growths. The density-modulated 3DEG has a low-temperature in-plane mobility in excess of 105 cm2/V s, compared to ∼2×105 cm2/V s for the uniform 3DEG. Capacitance-voltage measurements directly reveal the modulation of the density of the electron gas in the parabolic well with superimposed superlattice, and the absence of any density modulation for the gas in the bare parabolic well.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2422-2424 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction between surface acoustic waves and high mobility quasi-two-dimensional electron systems (2DES) in GaAs/AlGaAs heterojunctions with variable carrier density is investigated experimentally. In specially designed samples the strength of this acoustoelectric interaction can be controlled via the field-effect induced variation of the carrier density of the 2DES. Since the sensitivity of surface acoustic wave experiments is particularly high at very low conductivities, the proposed technique will be an especially valuable tool for the investigation of 2DES with extremely low sheet carrier densities. We demonstrate that the proper use of a metallic gate electrode does not conflict with the piezoelectric interaction between the mobile carriers confined in the heterostructure and the surface acoustic wave propagating on the piezoelectric substrate. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 348-350 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have designed and fabricated a remotely doped "logarithmic'' potential well intended to have a tunable, narrow band absorption at far-infrared frequencies. A surface gate, epitaxially grown backgate, and contact to the electron gas in the quantum well allow independent control of the absorption frequency and the integrated absorption strength. The resonance frequency is dominated by the well curvature at the potential minimum and can be Stark shifted from ω/2πc=35 cm−1 to a frequency of 125 cm−1 by moving the electron gas through the asymmetric well.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2226-2228 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We observe the infrared absorption of holes in a wide graded AlxGa1−xAs parabolic quantum well to be at a single frequency, independent of the number of holes in the well. The resonant absorption frequency appears to be determined by the light hole mass, not the heavy hole mass.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1003-1007 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The carrier distributions in modulation-doped wide graded quantum wells that a measurement of the capacitance C between a surface gate and an ohmic contact to the carriers as a function of the applied bias V would yield are calculated. These capacitance-voltage (C-V) distributions are found to agree inexactly, but closely, with the calculated true carrier distributions. Density modulation features, induced by superlattices or by abrupt changes in the curvature of band-gap grading, are strikingly reproduced. Electron distributions extracted from actual measurements on a wide parabolic well and on a parabolic well with superimposed superlattice are in good agreement with theory. For the case of the parabolic well, the occupancy of a finite number of subbands is manifested as structure in the C-V distributions. This technique is relevant to the measurement of carrier distributions in any wide carrier system with more than one electric subband occupied.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2370-2375 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Remotely doped graded parabolic potential well structures have been grown and studied. Electrons distribute themselves uniformly in a parabolic well, the density being proportional to the curvature or quasidoping in the well. Quasidoped semiconductors are synthesized by molecular beam epitaxy in the GaAs/AlXGa1−XAs system through the digital alloy technique. The analog grading produced by the digital alloy is verified by photoluminescence excitation spectroscopy. Low temperature mobility measurements show higher mobility in these quasidoped semiconductors than in similar real-doped semiconductors. Alloy-disorder scattering is suggested to be the mobility-limiting mechanism in this digital alloy system. Capacitance–voltage profiling analysis of quasidoped semiconductors has been developed, and is used to measure carrier profiles in these structures.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3731-3733 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An optoelectronic effect based on Faraday or Kerr rotation and the quantum-confined Stark shift is demonstrated. It is novel in that the degree of rotation is controlled by an electric field as opposed to a magnetic field. By applying an electric field to a quantum well structure, the Faraday rotation can be tuned into resonance, thereby varying the rotation angle of plane polarized light. We have observed a resonant rotation of 10° in GaAs at a magnetic field of 1 T. By applying a gate voltage of 2 V to a GaAs/AlGaAs superlattice structure, we observed a change in rotation of 1.3° at 2 K. The Faraday–Stark effect could be useful in electrically controlled light switches and high-speed optical modulators. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1972-1974 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intense radiation with photon energy of a few meV can induce the capture of electrons by DX centers in AlxGa1−xAs:Si.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 454-456 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Remotely doped parabolic quantum wells have been used to produce thick (〉2000 A(ring)) layers of high-mobility electron systems. Using a front gate electrode we are able to simultaneously deplete the well and change the actual thickness of this quasi-three-dimensional system. Thus, we can successively depopulate the elecrical subbands in the well, leading to step-like changes in the gate to channel capacitance. This yields direct insight into the subband structure of the electron system and allows its spectroscopy without the need of a magnetic field. The experimental results are compared with those of a self-consistent subband calculation and we obtain a qualitative agreement.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3165-3167 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Well-defined plasma oscillations are observed in a superlattice miniband even though the Fermi energy lies in the minigap. Despite the complex band structure, the resonance shows a remarkable insensitivity to changes in the number of electrons in the parabolic well in which the superlattice is placed, a feature of the generalized Kohn theorem that is expected only in the limit that the Fermi energy is near the bottom of the lowest miniband. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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