Some aspects of exciton thermal exchange in InAs quantum dots coupled with InGaAs/GaAs quantum wells

Photoluminescence (PL), its temperature and excitation power dependences, and PL excitation spectra have been investigated in InAs quantum dots (QDs) embedded in In0.15 Ga0.85 As/GaAs quantum wells (QWs) as a function of QD density. The QD density varied from 1.1× 1011 down to 1.3× 1010 cm-2 with the increase in QD growth temperature at the molecular beam epitaxy processing. A set of rate equations for exciton dynamics (relaxation into QWs and QDs, and thermal escape) has been solved to analyze the mechanism of PL thermal quenching in studied structures. Three stages have been revealed in thermal decay of the PL intensity of InAs QDs. Presented mathematical analysis provides the explanations of the mechanism of PL thermal decay as well as the peculiarities of PL excitation power dependences and PL excitation spectra. A variety of activation energies of PL thermal decay and the localization of nonradiative defects in InGaAs/GaAs QW structures with different InAs QD density are discussed as well.