Quantum dot exciton dynamics through a nanoaperture: Evidence for two confined states

Excitons confined to CdSe/ZnSe self-assembled quantum dots are probed throu gh a nanoaperture using time-resolved photoluminescence. Significant eviden ce is shown that two different electronic states are associated with these dots, with binding energies which differ by an order of magnitude. The firs t has a short 450 ps lifetime, exhibits a relatively broad emission line, a nd persists nearly to room temperature; the second exhibits a long (>4 ns) lifetime and is responsible for the sharp (similar to 100 mu eV) lines seen at low temperatures (<60 K). These results are completely unlike those see n in III-V dots, and reveal the complexity of the electronic structure in C dSe dots.