Münster 1999 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 4: Heterostrukturen I
HL 4.4: Vortrag
Montag, 22. März 1999, 11:15–11:30, H3
Cyclotron Resonance in Disordered Quasi Two-dimensional Electron Systems in GaAs/AlGaAs-Heterostructures in High Magnetic Fields — •R. Sellin1,2, M. Widmann2, U. Merkt2, G. Martinez1, and K. Eberl3 — 1High Magnetic Field Laboratory, Grenoble, France — 2Institut für Angewandte Physik, Universität Hamburg, Germany — 3MPI für Festkörperforschung, Stuttgart, Germany
We examine the line shapes of cyclotron resonance (CR) in modulation doped GaAs/AlGaAs heterojunctions in which a δ-doped layer of negatively charged beryllium acceptors acts as an adjustable source of potential fluctuations in the plane of the quasi two-dimensional electron system. In the magnetic quantum limit (ν <1), a CR line with anomal resonance energy and lineshape behavior is observed. The anomalies correspond to a blueshift of the CR mode matching the dispersion relation of ω+-transitions between the energy levels of a single conduction electron in a two-dimensional parabolic well (Fock-Darwin levels) in the quantum limit. In addition, one oberves a density-dependent down-bending of the dispersion ωCR(B) near the reststrahlen region of GaAs, linewidth anomalies as well as intensity fluctuations below and above this region. A model treating disorder and electron-electron interaction on an equal footing as well as simulations of the dielectric properties of all layers of the heterostructure and consideration of the resonant and non-resonant polaron effect are applied to elucidate the experimental results.