Controlling hole spin relaxation in charge tunable InAs/GaAs quantum dots.

We report on optical orientation of excitons and trions (singly charged excitons) in individual charge-tunable self-assembled InAs/GaAs quantum dots (QD). When the number of electrons varies from 0 to 2, the trion photoluminescence under quasi-resonant excitation gets progressively polarized from zero to ∼ 100%. We discuss this behavior as the quenching of the anisotropy induced exciton spin quantum beats due to the trion formation. This indicates a long hole spin relaxation time larger than the radiative lifetime, confirmed by time-resolved photoluminescence measurements carried out on a QD ensemble. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]