Interdot energy transfer in a system of coupled InAs/GaAs quantum dots

We present new results concerning the carrier transfer between quantum dots (QDs) in dense InAs/GaAs QD arrays with a bimodal size distribution explored by means of steady-state and time-resolved photoluminescence (PL). Interdot carrier transfer involves transitions from the ground state of small QDs into lower lying states of larger QDs, a relaxation channel that saturates at high excitation densities. A staircase-like spectral dependence of the PL decay time is observed and analyzed by taking into account the bimodal QD size distribution. We show that monitoring the spectral behavior of the ground-state PL time constants offers a new and independent tool for distinguishing between PL contributions from different dot size families.