Probing the carrier transfer processes in a self-assembled system with In_0.3Ga_0.7As/GaAs quantum dots by photoluminescence excitation spectroscopy

In this report we present experimental studies on the energy transfer between the wetting layer and single large elongated In_0.3Ga_0.7As/GaAs quantum dots. We obtain insight into the electronic and optical properties of In_0.3Ga_0.7As/GaAs quantum dots by probing their confined electronic states via photoluminescence excitation spectroscopy on the single dot level. We demonstrate that the energy separation between the states of a quantum dot and the wetting layer states affects the carrier transfer efficiency - reduced transfer efficiency is observed for smaller dots with higher indium content. We also discuss the effects of the excited states and the trapping of carriers on confinement potential fluctuations of the wetting layer. Eventually, the transfer of charge carriers from localized wetting layer states to a single quantum dot is evidenced in temperature-dependent photoluminescence excitation spectroscopy.