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  • Articles: DFG German National Licenses  (26)
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  • Articles: DFG German National Licenses  (26)
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  • 1
    Electronic Resource
    Electronic Resource
    Interaction of surface acoustic waves with a two-dimensional electron system in a LiNbO3-GaAs/AlGaAs sandwich structure (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2213-2215 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe a simple, contactless method to study the interaction of surface acoustic waves (SAW) with a two-dimensional electron system (2DES) in GaAs/AlGaAs heterostructures at low temperatures and in high magnetic fields. The heterostructure is part of a sandwich structure on a Y-cut Z-propagating LiNbO3-SAW-delay line. The interaction of the SAW with the 2DES leads to quantum oscillations of the SAW amplitude as a function of the applied magnetic field which can be used to characterize the sample and to investigate the transport properties of the 2DES.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341685
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Wide electron gas with periodic density modulation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1460-1463 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.351708
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Gate-controlled subband structure and dimensionality of the electron system in a wide parabolic quantum well (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 454-456 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.102763
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Nonlinear acoustoelectric interactions in GaAs/LiNbO3 structures (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 965-967 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface acoustic waves accompanied by very large piezoelectric fields can be created in a semiconductor/piezoelectric hybrid system. Such intense waves interact with the mobile carries in semiconductor quantum well structures in a manner being strongly governed by nonlinear effects. At high sound intensities, a formerly homogeneous two-dimensional electron system breaks up into well confined stripes surfing the wave. As a result, we observe a strong reduction of electronic sound attenuation. On the other hand, large momentum transfer between the electron system and the wave results in nonlinear acoustoelectric effects and acoustoelectric amplification. We describe our experimental findings in terms of a generalized theory of the acoustoelectric effect and discuss the importance for possible device applications. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124568
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  • 5
    Electronic Resource
    Electronic Resource
    Spatially resolved exciton trapping in a voltage-controlled lateral superlattice (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 154-156 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: With spatially resolved photoluminescence experiments we demonstrate voltage-controlled trapping of excitons in a submicron scale lateral potential superlattice imposed on a semiconductor quantum well. The potential modulation is achieved by two interdigitated field-effect electrodes on top of the sample surface. Both parallel and vertical electric field components strongly modify the optical properties of the quantum well. We show that the lateral modulation of the strength of the quantum confined Stark effect results in an effective lateral exciton potential that can be probed by spatially resolved measurements of the excitonic luminescence. We demonstrate that excitons may be confined to the regions of strongest vertical fields, in which the effective exciton energy is lowest. Spatial resolution of the observed photoluminescence signal allows for a qualitative understanding of the exciton transport and trapping process. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121740
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  • 6
    Electronic Resource
    Electronic Resource
    Giant acoustoelectric effect in GaAs/LiNbO3 hybrids (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2128-2130 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The acoustoelectric effect in a hybrid of a strong piezoelectric material and a semiconductor layer containing a two-dimensional electron system is investigated. Caused by the very strong interaction between a surface acoustic wave and the mobile carriers in the semiconductor, the acoustoelectric effect is very large as compared to other materials, which might be interesting for device applications. Moreover, the tunability of the sheet conductivity of the electron system enables us to tune the magnitude of the acoustoelectric effect over a wide range. We present experimental results for a GaAs/LiNbO3 layered hybrid system at room temperature and describe our experimental findings quantitatively using a recently developed model calculation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122400
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  • 7
    Electronic Resource
    Electronic Resource
    Single-chip fused hybrids for acousto-electric and acousto-optic applications (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2097-2099 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The combination of the electronic and optical properties of a semiconductor hetero-junction and the acoustic properties of a piezoelectric substrate material yields a new class of very promising hybrids for potential acousto-electric and acousto-optic applications. LiNbO3/GaAs hybrids have been fabricated using the epitaxial lift-off technique resulting in unusually large acousto-electric and acousto-optic interaction between the quasi two-dimensional electron system in the semiconductor and surface acoustic waves on the piezoelectric substrate. Field effect tunability of the interaction at room temperature is demonstrated and possible device applications are discussed. Photoluminescence measurements show the influence of the acousto-electric fields on the optical properties of quantum well structures. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118960
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  • 8
    Electronic Resource
    Electronic Resource
    Voltage tunable acoustoelectric interaction in GaAs/AlGaAs heterojunctions (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2422-2424 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.112694
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Imaging of acoustic charge transport in semiconductor heterostructures by surface acoustic waves (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 4139-4141 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate room-temperature acoustic charge transport of electrons and holes in an InGaAs/GaAs heterostructure. The carriers are optically generated by interband absorption and then separated, stored, and transported in the piezoelectric potential superlattice of a surface acoustic wave. The charge distribution is detected with a spatial resolution of a few acoustic wavelengths by a second orthogonal probe beam, genererated by so-called tapered transducers. The image information is given as a phase shift signal in frequency space and allows for the direct comparison of the number of generated and transported carriers. Regions of mere carrier drag and full carrier capture and transport are observed simultaneously. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125562
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  • 10
    Electronic Resource
    Electronic Resource
    X-ray imaging and diffraction from surface phonons on GaAs (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1709-1711 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface acoustic waves (SAWs) are excited on the GaAs (001) surface by using interdigital transducers, designed for frequencies of up to 900 MHz. The emitted phonons with wavelengths down to 3.5 μm are visualized and characterized by combined x-ray diffraction techniques. Using stroboscopic topography, the SAW emission of a parallel and a focusing transducer geometry are imaged. High-resolution x-ray diffraction profiles show up to 12 phonon-induced satellite reflections besides the GaAs (004) reflection, with a width of 9 arcsec each. The diffraction pattern is simulated numerically, applying the kinematical scattering theory to a model crystal. From fits to measured diffraction profiles at different excitation voltages, the SAW amplitudes were calculated and found to be in the sub-nm range. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124797
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