Dynamics of inter- and intra-growth-island exciton localization in GaAs single quantum wells

A distinct two-exponential decay of excitonic transitions in coherent GaAs single quantum wells with atomically flat terraces is observed by time-resolved photoluminescence under direct excitation. The measured two-component time behavior is a direct consequence of the in-plane exciton localization due to the inter- and intra-growth-island exciton transfer. These interesting time behaviors are found to be strongly dependent on the emission energy at low temperatures, but the dependence disappears when excitons are delocalized and become mobile by thermal activation.