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HL: Halbleiterphysik

HL 39: Ultrakurzzeitph
änomene I

HL 39.8: Vortrag

Donnerstag, 27. März 2003, 12:45–13:00, BEY/81

Avalanche breakdown in GaAs pin-diodes observed on a fs time scale — •O. Schmidt¹, A. Schwanhäusser¹, M. Eckardt¹, S. Malzer¹, G.H. Döhler¹, M. Betz², S. Trumm², and A. Leitenstorfer² — ¹Institut für technische Physik I, Universität Erlangen-Nürnberg, Erwin-Rommel-Str.1, 91058 Erlangen, Germany — ²Physik-Department E11, Technische Universität München, D-85748 Garching, Germany

In this contribution we present a novel experimental technique and first experimental results on the exploration of the avalanche breakdown in GaAs with femtosecond time resolution.

The time resolution is achieved by a unique two color fs pump and probe laser source. Our bandgap engineered AlGaAs pin heterostructures allow for spatial selective carrier injection by a wavelength adapted pump pulse. In the case of sub critical field strength (approx. 450kV/cm), we gain information about the carrier transport by probing the transmission change of the sample, with a delayed probe pulse [1], (transient Franz-Keldysh effect). When field is increased and avalanche multiplication sets in, an increasing number of electrons and holes contribute to the screening, resulting in an increased signal. But also the time dependence of our signal changes. While sub critical fields lead to a signal saturating when all carriers have left a defined probe stretch, when field is critically increased impact ionised electrons and holes propagating in opposite directions retard the saturation of the signal drastically.

[1] A. Schwanhäußer, M. Eckardt, M-Betz, et. al., Physica B 314 (2002), 273