Abstract

The application of an electric field normal to the layers of a superlattice (SL) was predicted to break the continuous mini band into a set of discrete levels, known as Stark ladder, and to localize the elektron wave function, which is extended throughout the SL at zero field, into a limited number of neighboring sites.^[1] This fundamental prediction was recently confirmed when discrete peaks were observed in the optical properties of semiconductor SL in the presence of an electric field.^[1,2] In this paper we use time resolved differential absorption spectroscopy to investigate the electron transport through a SL subjected to localizing electric field. We show that the traversal time through the SL increases at moderate fields and then decreases at large fields. We interpret this behavior as an evidence for a Wannier-Stark localization.

© 1992 IQEC