Carrier-relaxation process in time-resolved up-converted photoluminescenceat ordered (Al0.5Ga0.5)(0.5)In0.5P and GaAs heterointerface

Up-converted photoluminescence (UPL) was observed at the long-range ordered (Al0.5Ga0.5)(0.5)In0.5P/GaAs(001) heterointerface, during the excitation o f GaAs. Excitation-power dependence of the UPL intensity reflects carrier-l ocalization properties caused by potential fluctuations due to a multidomai n structure in the ordered (Al0.5Ga0.5)(0.5)In0.5P. When we excited the GaA s layer, photoexcited carriers spatially transferred to the (Al0.5Ga0.5)(0. 5)In0.5P layer and relaxed from higher lying states to lower lying states i n the fluctuated potential. Time-resolved measurements were performed for t he UPL and normal photoluminescence (NPL) excited by an above-gap light. We observed a slowly rising component in the time-resolved UPL, whereas the N PL showed an exponential decay profile. These results reveal chat the carri er-relaxation processes are different near the surface and near the interfa ce of the epitaxial layer.