Time-resolved photoluminescence of a triple GaAs quantum well with growth islands under resonant photoexcitation into the ground and excited states

Exciton radiative recombination properties of an electronically isolated triple GaAs quantum well (QW) with different thicknesses prepared by growth-interrupted molecular beam epitaxy have been investigated with respect to the effect of growth islands present in each QW. When cold excitons with a negligible center-of-mass motion are resonantly photoexcited within each dominant island terrace, the photoluminescence (PL) dynamics of the split exciton lines reflect the exciton intra-well transfer towards the wider-well terraces. However, dramatic changes are observed in both the PL intensity distribution and the dynamics between the QWs as well as between the island terraces under resonant excitation into an excited (n=2) state of the widest well located just below the barrier band edge. We tentatively attribute the origin of these changes to the different exciton relaxation pathways in terms of center-of-mass kinetic motion of the two-dimensional excitons.