Münster 1999 – scientific programme

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HL: Halbleiterphysik

HL 23: Poster II

HL 23.13: Poster

Wednesday, March 24, 1999, 14:00–18:00, Z

Ballistic electron transport in high mobility Al_xGa_1−xAs/GaAs-heterostructures patterned by etching or focused ion beam implantation — •Dorina Diaconescu, Sascha Hoch, Dirk Reuter, and Andreas D. Wieck — Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum

We have investigated the electron transport at low temperatures in high mobility two-dimensional electron gases at Al_xGa_1−xAs/GaAs heterojunctions. The electron mobility was 2.56×10⁶ cm²/Vs at 1.1 K temperature. The mobility was increasable by illumination up to 5.44×10⁶ cm²/Vs. Ballistic electron transport was proved for macroscopic four-terminal mesa structures. Such measurements yielded a ballistic length of approximately 36 µ m. With Hall experiments we deduced the mean free path length including small angle scattering to be 60 µ m.

Using maskless focused ion beam implantation technique (FIB) narrow channels can very easily be defined for electron confinement. With FIB-written gates we realized point contacts of 1 − 2 µ m width to observe electron beam collimation. The effective width of a point contact can be controlled applying a gate-voltage.

Using a magnetic field perpendicular to the two-dimensional electrongas it was possible to observe the fundamental and first skipping orbit in focusing experiments. This proves the specularity properties of the FIB lines.

This work has been performed with the framework of Graduiertenkolleg 384.