Subband-resonance oscillations in undoped type-II superlattices under photoexcitation

Subband-resonance oscillations have been observed in photoexcited, undoped type-II GaAsAlAs superlattices. The frequency can be tuned over a wide range either by the applied voltage or the photoexcited carrier density. The oscillations can be explained by an oscillating space-charge which forms the domain boundary between two electric-field regions, which are attributed to negative differential velocity originating from X-related resonant tunneling.