Exciton lifetime and spin dynamics in type-I In1−xAlxAs/Ga0.67Al0.33As quantum dots: Photoluminescence and pump-probe experiments

The exciton lifetime and spin relaxation have been studied in self-assembled In1−xAlxAs/Ga0.67Al0.33As quantum dots (QDs). Time-resolved photoluminescence and resonant pump-probe measurements were performed, at variable temperature and for different QD aluminium compositions. At low temperature, a long exciton-spin relaxation time has been measured, in agreement with the QD zero-dimensional confinement and the quenching of the relaxation mechanisms. The existence of a quasi-2D regime, in sample with a high QD density, has been observed. The importance of thermally-activated processes toward excited states is also evidenced, for QDs with different compositions and sizes.