Temperature-dependent photoluminescence of self-assembled (In,Ga)As quantum dots on GaAs (100):: Carrier redistribution through low-energy continuous states

Temperature-dependent photoluminescence (PL) studies of an ensemble of self-assembled (In,Ga)As quantum dots (QDs) on GaAs (100) provide insight into the nature of the continuous states between the wetting layer (WL) and QDs. In addition to the well-known anomalous temperature dependence of the PL peak position and width around 90 K due to carrier (electron-hole pair) redistribution through the WL, we observe a similar behavior at much lower temperatures around 30 K. This behavior is attributed to carrier redistribution through the low-energy continuous states between the WL and QDs, directly proving their quasi-two-dimensional character. The smaller changes in the PL spectra than the WL-induced ones, however, indicate that the carrier redistribution and, thus, the spatial extent of the continuous states are restricted to a limited area around the QDs. This is also supported by the constant integrated PL intensity in this temperature range due to the absence of nonradiative recombination within these areas.