Regensburg 2013 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 29: Poster Session: Spintronics; Spin-controled transport; Topological insulators; Interfaces / Surfaces; Magnetic semiconductors
HL 29.12: Poster
Monday, March 11, 2013, 16:00–20:00, Poster A
Optical spin polarization of donor electrons through donor bound exciton states in ZnO — Sebastian Kuhlen1, •Ralph Ledesch1, Christoph Schwark1, Vera Klinke1, Christian Weier1, Gernot Güntherodt1, Matthias Althammer2, Sebastian T. B. Gönnenwein2, Matthias Opel2, Rudolf Gross2, Thomas Wassner3, Martin S. Brandt3, and Bernd Beschoten1 — 1II. Physikalisches Institut A, RWTH Aachen University, Aachen — 2Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching — 3Walther Schottky Institut, Technische Universität München, Garching
ZnO exhibits a large variety of natural dopants, which present a promising playground for coherent spintronics as each donor type presents an individual spin state with different spin lifetimes and Landé factors. Furthermore, long spin dephasing times as high as 20 ns have been observed. We demonstrate that the electrons can be polarized by optical pumping and detected using the Faraday effect in a standard pump-probe experiment. We furthermore observe that the polarization mechanism is most effective when the pump photon energy matches one of various donor bound exciton state energies, while the spin dephasing time exceeds the exciton lifetime by several orders of magnitude. Hence we conclude that electron spins are polarized by optical selection rules during the transition to the exciton state, but are eventually transferred to the donor electron of the impurity to which the exciton has been bound.
Work supported by DFG through SPP 1285.