TUNNELING RESONANCES AND MINIBAND CONDUCTION IN SUPERLATTICES

Transient photoconduction of photoexcited carriers in an electric field perpendicular to the layers of GaAsAlAs superlattices has been investigated. The transit times for electron transport were clearly resolved. The time evolution of the transient photocurrent for different excitation conditions was analyzed. The field dependence of the transit times shows local minima which are associated with resonant tunneling processes between different conduction subbands. Moreover, the time dependence of the photoluminescence is strongly affected by these transport processes. At low electric fields, we observed additional structure in the conduction properties arising from the occurrence of minibands and determined drift mobilities for miniband conduction. We found experimental evidence that hole tunneling can become important if the valence subbands are at resonance and the conduction subbands are off resonance. © 1990.