Impact of wetting-layer density of states on the carrier relaxation process in low indium content self-assembled (In,Ga)As/GaAs quantum dots

Abstract

Carrier relaxation processes have been studied in low indium content self-assembled (In,Ga)As/GaAs quantum dots (QDs). Temperature-dependent photoluminescence of the wetting layer (WL) and QDs, and QD photoluminescence rise time elongation from $\ensuremath{\sim}$100 to $\ensuremath{\sim}$200 ps in the range of 10--45 K, indicated a complex carrier relaxation scheme. It involves localization of carriers/excitons in the WL, their temperature-mediated release, and subsequent transfer between the states of the WL and QD ensemble. These observations are explained by a thermal hopping model, in which electron-hole pairs are redistributed within two separate sets of zero-dimensional states of considerably different densities connected by a two-dimensional mobility channel.