Exciton dynamics within growth islands of GaAs/Al0.17Ga0.83As single quantum wells

We have directly observed the localization dynamics of excitons within growth islands of a GaAs/${\mathrm{Al}}_{0.17}$ ${\mathrm{Ga}}_{0.83}$As single quantum well by time-resolved photoluminescence (PL). The PL emission of each growth island is split into two peaks that have an energy separation of 3 meV. These peaks are attributed to the emission of free and localized excitons within the islands. Upon pulsed excitation, the high-energy free-exciton PL line dominates the initial emission, while for longer times (350 ps) the bound-exciton PL peak emerges. This observation directly reflects the localization of free excitons within the growth islands.