Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 9: Poster I

HL 9.103: Poster

Montag, 27. März 2006, 15:15–17:45, P3

Anisotropic magnetization and magnetotransport studies of two- and three-dimensional electron systems in GaAs — •A. Krohn, J. I. Springborn, Ch. Heyn, and D. Grundler — Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Jungiusstraße 11, 20355 Hamburg, Germany

The low-temperature magnetization M of quasi-free electrons in conducting metals and semiconductors exhibits the well-known de Haas-van Alphen (dHvA) oscillations which originate from the Landau quantization of the electronic spectrum in a magnetic field B. While the dHvA effect is isotropic for a three-dimensional system (3DES) of free electrons, it is anisotropic for a two-dimensional electron system (2DES). In our experiment we have examined different electron systems realized in Si-doped epitaxial GaAs layers where the thickness was varied from 20 nm (2DES) to several µm (3DES). The carrier density was adjusted to be similar and about 10¹⁸ cm⁻³. The mobility was about 2 × 10³ cm²/Vs. We measured the dHvA oscillations by detecting the torque τ = M × B acting on a highly sensitive cantilever magnetometer. This technique was in particular sensitive to anisotropic magnetization. At the same time we evaluated the Shubnikov-de Haas oscillations from magnetotransport measurements. All data were taken at B up to 14 T and temperatures T<5 K. We found that also the thick samples exhibited a surprisingly anisotropic magnetization, even for a layer thickness as large as several hundred nm. We thank D. Heitmann for continous support and acknowledge financial support by the Deutsche Forschungsgemeinschaft via SFB 508 and via GR1640/1-3.