Impact of carrier redistribution on the photoluminescence of CdTe self-assembled quantum dot ensembles

We report on the photoluminescence (PL) measurements of two structurally different CdTe self-assembled quantum dot (QD) samples. These include CdTe QD’s connected with the uniform two-dimensional wetting layer (WL) and fully developed CdTe QD’s that are isolated from each other. Both temperature and excitation power dependencies found for the ensemble of fully developed QD’s reflect that of individual QD’s. In this case, no signature of intradot carrier redistribution is observed even at 120 K. In contrast, both continuous-wave and time-resolved PL show the presence of strong thermally induced carrier redistribution for the structure, where the dots are connected by a uniform two-dimensional WL. In particular, three distinct temperature regions are identified. At temperatures below 30 K, dots in the ensemble are isolated from each other: the emission occurs only from QD’s occupied initially by both electron and hole. When temperature increases $(T>\mathrm{}30\mathrm{}\mathrm{K}),$ the carriers from QD’s are thermally activated into the uniform WL and are subsequently captured by other QD’s. Finally, above 100 K the nonradiative recombination in the WL prevents the capture of thermally activated carriers. These results, while providing a thorough understanding of the optical properties of QD structures, give also important information about structural complexity of epitaxially grown II-VI semiconductor QD’s.