Evolution of the electronic states of In_x,Ga_1−xAs/GaAs superlattices in the presence of an external d.c. electric field

Abstract

We discuss recent measurements of photomodulated and electromodulated spectroscopy (77 K) as well as photoexcitation luminescence (2 K) in some In.Ga_1−xAs/GaAs superlattices. Our results show clear evidence of Franz Keldysh and Stark-Wannier regimes for different samples and field values. In one of the samples, light and heavy holes are shown to be in different field regimes simultaneously. These studies support the idea that band line-up at the heterojunction is always such that the light holes are essentially unconfined.