Optical orientation of electron and nuclear spins in strain free GaAs quantum dots grown by droplet epitaxy

Abstract

We report optical orientation experiments in individual, strain free GaAs quantum dots in AlGaAs grown by modified droplet epitaxy. Circularly polarized optical excitation yields strong circular polarization of the resulting photoluminescence at 4 K. Optical injection of spin polarized electrons into the dot gives rise to dynamical nuclear polarization that considerably changes the exciton Zeeman splitting (Overhauser shift). We show that the created nuclear polarization is bistable and present a direct measurement of the build‐up time of the nuclear polarization in a single GaAs dot in the order of a second. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)