Ultrafast Luminescence Studies in InAs Quantum Dots

We report results of our investigation on the carrier capture and relaxation processes in InAs/GaAs QDs at room temperature by a time-resolved photoluminescence spectroscopy with a time resolution of ~ 200 fsec. Carrier capture into the wetting layer and confined states of the dots is investigated. The rising processes are assigned to the carrier capture from the barriers into the wetting layer and confined states in InAs dots and subsequent relaxation in each detected energy level. We found that, under high excitation intensity, electronic states in the dots were populated mainly by carriers directly captured from the barrier. However, at low excitation densities, the PL rise times were influenced by the carrier diffusion.