OPTICALLY-DETERMINED EXCITON TRANSPORT IN GAAS STRUCTURES

We have used an all-optical photoluminescence-imaging technique to mea sure excitonic transport in three types of GaAs structures in which th e excitonic transitions vary from allowed direct-gap excitons to forbi dden, doubly-indirect Type-II excitons. We find remarkable differences in the transport properties of these excitons. Our studies show that bulk free-exciton transport exhibits an anomalous laser power-dependen t diffusivity, whereas quasi-2D interfacial excitons and Type-II cross -interface excitons do not. Additionally, we observe localization of c ross-interface excitons at the potential disorder induced by the heter ointerface roughness.