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DY: Dynamik und Statistische Physik

DY 46: POSTER II

DY 46.7: Poster

Thursday, March 30, 2000, 15:00–18:00, D

Microwave-induced patterns in n-GaAs — •V. Novák¹, D. Mac Mathúna², J. Hirschinger², and W. Prettl² — ¹Institute of Physics AS CR, Cukrovarnická 10, 162 00 Prague — ²Institut für Experimentelle und Angewandte Physik, Universitätsstraße 31, 93053 Regensburg

Moderately doped semiconductors become almost insulating at temperature of liquid Helium due to the freeze-out of free carriers. If biased above certain critical voltage, the material exhibits an electric breakdown accompanied by the formation of current carrying filaments. Structures analogous to current filaments can be found, if a contactless sample of the material is subject to microwave electric field. Unlike the filaments the microwave-induced structures do not bear the enforced symmetry of the contacts. Instead, complex patterns can be observed to arise, depending on the frequency and the intensity of the microwave irradiation. Experiments have been carried out to determine the pattern forming mechanism, and a numerical model has been constructed, which reproduces some of the observed phenomena.