Carrier capture and relaxation in InAs quantum dots

Abstract

We have investigated the carrier capture and relaxation processes inInAs/GaAs self-assembled quantum dots at room temperature bytime-resolved photoluminescence techniques with a high time resolution of∼200 fs. Following the initial fast relaxation in GaAs barriers, we have observed rising processesin time-resolved PL intensity at the energies of quantum dot confined states and thewetting layer. The rising processes are assigned to the carrier capture from the barriers intothe wetting layer and confined states in InAs dots and subsequent relaxationin each detected energy level. We found that the carrier capture rate is fasterthan the intra-dot relaxation within the range of excitation densities that weinvestigated. Under high excitation intensity, the electronic states in the dots werepopulated mainly by carriers directly captured from the barrier. However, at lowexcitation densities, the PL rise times were influenced by the carrier diffusion.