Spin Dynamics In Self-Assembled Quantum Dots Coupled With A Diluted Magnetic Semiconductor

We study the spin dynamics in self-assembled quantum dots (QDs) coupled with a diluted magnetic semiconductor (DMS) layer, where spin-polarized excitons can be injected from the DMS into QDs. Excitonic photoluminescence in the coupled QDs shows an increase in the degree of circular polarization P up to 0.3 at 5 T with increasing time after the excitation with a linearly polarized light pulse, indicating the spin injection dynamics from the DMS. The P-value turns to decay gradually after reaching its maximum, resulting from the spin relaxation in the QDs. We find that an inter-dot energy transfer affects the observed P-value. From a rate equation analysis, we deduce time constants responsible for the exciton-spin injection in the coupled QD system. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim