Ultrafast carrier capture and relaxation in modulation-doped InAs quantum dots

Abstract

We report investigations on carrier capture and relaxation processes in undoped and modulation-doped InAs∕GaAs self-assembled quantum dots (QDs) by using time-resolved spectroscopy technique with a time resolution of ∼200fs. We find that carrier capture and relaxation in the ground state of the charged QD are faster compared to the undoped dots even at an excitation level as low as 1×1010cm−2. It is attributed to the triggering of the vibrating polarization field induced by the presence of cold carriers in the doped dots. The rate of an electron been captured by a positively charged QD is also calculated based on our proposed model.