Vertical transport in GaAs/Ga1-xAlxAs superlattices observed by photoluminescence

Photoluminescence experiments on GaAs/Ga_1-xAl_xAs small period superlattices in which enlarged wells have been purposely introduced reveal a transfer of photoexcited carriers from the superlattice to the enlarged well localized levels. The transfer efficiency characterized by the relative intensities of luminescence peaks increases when the superlattice period decreases. Within a simple model, ionized impurity scattering and well size fluctuations account for this carrier transfer.