Effects of p-doping on excited spin states and the dynamics in InGaAs quantum dots

We study effects of p-doping on excited spin dynamics of InGaAs quantum dots (QDs) by circularly polarized time-resolved photoluminescence (PL). At excited states of p-doped QDs, the circular polarization degree (CPD) values are twice higher than those of undoped QDs. We attribute this enhanced CPD at excited states to spin-selective energy relaxation from the excited states to ground state. This can be promoted by the suppression of state filling at the ground state, which is induced by the decrease of PL lifetime due to the resident hole population.