INFLUENCE OF TYPE-I TO TYPE-II TRANSITION BY AN APPLIED ELECTRIC-FIELD ON PHOTOLUMINESCENCE AND CARRIER TRANSPORT IN GAAS ALAS TYPE-I SHORT-PERIOD SUPERLATTICES/

We have investigated the influence of type-I to type-II transition by an applied electric field on photoluminescence and carrier transport b y time-of-flight experiments in GaAs/AlAs short-period superlattices. Type-I to type-II transition was confirmed by observing degenerated ph otoluminescence spectra caused by Gamma-X mixing. The rise time of the time-resolved photocurrent was found to increase by the type-I to typ e-II transition. This result clearly shows that the tunneling time thr ough type-II alignment is longer than that through type-I alignment. T he delayed carrier transport is most likely caused by Gamma-X-Gamma tr ansfer. The results suggest that in type-II superlattices, carriers pr efer Gamma-X-Gamma transfer to Gamma-Gamma sequential tunneling.