Thermal activation of excitons in asymmetric InAs dots-in-a-well InxGa1-xAs/GaAs structures

Photoluminescence, its temperature dependence, and photoluminescence excitation spectra of InAs quantum dots embedded in asymmetric InxGa1-xAs/GaAs quantum wells [dots in a well (DWELL)] have been investigated as a function of the indium content x (x=0.10-0.25) in the capping InxGa1-xAs layer. The asymmetric DWELL structures were created with the aim to investigate the influence of different barrier values at the quantum dot (QD)/quantum well interface on the photoluminescence thermal quenching process. The set of rate equations for the two stage model for the capture and thermal escape of excitons in QDs are solved to analyze the nature of thermal activation energies for the QD photoluminescence quenching process. The two stage model for exciton thermal activation was confirmed experimentally in the investigated QD structures as well. The localization of nonradiative defects in InAs/InGaAs DWELL structures is discussed on the base of comparison of theoretical and numerically calculated (fitting) results. (c) 2007 American Institute of Physics.