Time domain investigation on excitonic spectral diffusion in CdSe quantum dots grown on vicinal surface GaAs substrates

Two monolayers of CdSe sandwiched by ZnSe layers were grown by molecular-beam epitaxy on a vicinal GaAs surface substrate. Small ensembles of these self-assembled quantum dots (QD) have been studied at low temperatures using micro-photoluminescence spectroscopy. We observe reversible spectral diffusion in individual QD luminescence lines. The energy shift is negligibly small at low optical excitation power and amount to about 0.7 meV under higher excitation (0.6 kW/cm2). Because the energy shift is found to be significantly smaller than the exciton–biexciton splitting of CdSe QDs even under high excitation, the conventional spectral filtering could be used to effectively select the exciton-related emission from these QDs.