21 February 2012 Ultrafast nonlinear terahertz studies of high-field charge transport in semiconductors
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Proceedings Volume 8260, Ultrafast Phenomena and Nanophotonics XVI; 82600N (2012); doi: 10.1117/12.910178
Event: SPIE OPTO, 2012, San Francisco, California, United States
Abstract
Nonlinear terahertz (THz) spectroscopy gives insight into high-field charge transport in semiconductors. Strong THz transients with field amplitudes of up to megavolts/cm serve as a driving field for free carriers and the resulting transport behavior is directly inferred from the field radiated by the moving charges. We study the transition from a ballistic to a drift-like transport regime of electrons in bulk GaAs. While electrons in the lowest conduction band of an n-type sample display ballistic transport, a transition to a drift-like behavior is found in an optically generated electron-hole plasma. Time-resolved measurements reveal the onset of friction on a time scale of a few picoseconds, mainly due to interactions of electrons with the hole distribution heated by the intense THz driving field. Experiments in which photoexcited electrons undergo intervalley scattering from the Γ to the L valley reveal characteristic changes of the transport behavior due to the picosecond backscattering to the Γ valley. The experimental results are in agreement with theoretical calculations of the time-dependent friction including both electron-hole scattering and local-field effects.
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Thomas Elsaesser, Pamela Bowlan, Klaus Reimann, Michael Woerner, Rudolf Hey, Christos Flytzanis, "Ultrafast nonlinear terahertz studies of high-field charge transport in semiconductors", Proc. SPIE 8260, Ultrafast Phenomena and Nanophotonics XVI, 82600N (21 February 2012); doi: 10.1117/12.910178; https://doi.org/10.1117/12.910178
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KEYWORDS
Electrons

Terahertz radiation

Gallium arsenide

Plasma

Scattering

Picosecond phenomena

Semiconductors

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