Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 89: Optical Properties II

HL 89.8: Vortrag

Freitag, 18. März 2011, 12:15–12:30, POT 251

Optical orientation of Mn²⁺ ions in GaAs — •Lukas Langer¹, Ilya A. Akimov^1,2, Roslan I. Dzhioev², Vladimir L. Korenev², Yuri G. Kusrayev², Victor F. Sapega², Dmitri R. Yakovlev^1,2, and Manfred Bayer¹ — ¹Experimentelle 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.