PHOTOLUMINESCENCE UP-CONVERSION IN GAAS ALXGA1-XAS HETEROSTRUCTURES/

We propose GaAs/AlxGa1-xAs heterostructures as a model system to study the phenomenon of photoluminescence (PL) up-conversion and demonstrat e low-temperature up-converted PL (UPL) in these heterostructures. We find that a mechanism to prevent up-converted carriers in the AlxGa1-x As layer from thermalizing back to the GaAs layer is essential for eff icient UPL. We also find that neither a type-II band alignment nor exi stence of long-lived intermediate states is an essential requirement o f UPL. The results of time-resolved UPL measurements are interpreted w ithin the current models.