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Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 89: Optical Properties II

HL 89.8: Talk

Friday, March 18, 2011, 12:15–12:30, POT 251

Optical orientation of Mn2+ ions in GaAs — •Lukas Langer1, Ilya A. Akimov1,2, Roslan I. Dzhioev2, Vladimir L. Korenev2, Yuri G. Kusrayev2, Victor F. Sapega2, Dmitri R. Yakovlev1,2, and Manfred Bayer11Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany — 2A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia

We report on optical orientation of Mn2+ ions in bulk GaAs under application of weak longitudinal magnetic fields (B ≤ 150 mT ). The studied samples were grown by liquid phase epitaxy and Czochralski method and were doped with a low Mn acceptor concentration of 8 × 1018 cm−3. Time resolved measurements of circular polarization for donor-acceptor photoluminescence in Faraday geometry reveal nontrivial spin dynamics of donor localized electrons. Initially the degree of polarization of the electron spins is 40%. It then decays within some tens of ns to reach a plateau. The plateau is absent at B=0 T and saturates at B=150 mT reaching the value of 35%. It’s sign changes with the helicity of incident light. It follows that the s-d exchange interaction with optically oriented electrons induces a steady state non-equilibrium polarization of the Mn2+ ions. The latter maintain their spin and return part of the polarization back to the electron spin system, resulting in the plateau. This provides a long-lived electron spin memory in GaAs doped with Mn. The dynamical polarization of ionized Mn acceptors was also directly monitored using spin flip Raman scattering spectroscopy, in agreement with time-resolved data.

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