Origin of two types of excitons in CdSe dots on ZnSe

Recent micro-PL and time-resolved PL data performed on CdSe dots embedded in ZnSe show compelling evidence that the PL emission results from two different kinds of states. We propose a model explaining the origin of these different states coexisting within a single dot. The main concept of the model is that, while the ground state of the heavy hole is confined to strain-induced potential pockets at the bottom of the island, the electrons and the first excited state in the valence band are distributed within the entire island. That difference in the degree of localization between the two heavy-hole band states is responsible for the different properties of PL transitions observed in our experiments.