Phonon-assisted exciton spin relaxation in (In,Ga)As/GaAs quantum dots



In this work, we study the temperature-dependent spin relaxation of exciton-bound carriers in (In,Ga)As/GaAs quantum dots. The exciton population mapped by a time-resolved differential transmission signal reveals a decay on two different time scales, reflecting the fractions of optically active and inactive excitons. The underlying exciton states are split from each other by the exchange interaction. The phonon-assisted spin-orbit interaction induces spin flips of an exciton-bound electron or hole which convert the exciton populations into each other. The temperature-dependent relaxation rate follows a thermal phonon distribution. Deviations indicate that two-phonon processes involving higher orbitals may contribute significantly to the total relaxation process. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)