Abstract

Recently we reported a blue shift of the heavy-hole (HH) exciton in type-II superlattices in the quasi-steady-state. We explained the shift in terms of noncompensation of counteracting many-body effects in an electron-hole plasma which consisted of an electron plasma in the X-valley of the AlAs layers and a hole plasma in the Γ-valley of the GaAs layers.¹ This blue shift indicates that there is reduced compensation between bandgap shrinkage and reduction of the binding energy at high carrier densities. Here we report the first study of femtosecond optical nonlinearities of GaAs/AlAs type-II superlattices in an applied axial electric field. In this paper we present a study of the effect of electric field on the temporal evolution of the absorption spectra of highly excited type-II superlattices and report intriguing transient energy shifts of the HH exciton. We discuss these phenomena in terms of modifications of the many-body plasma effects caused by electron and hole distributions functions that depend on electric-field-dependent Γ-X splitting.

© 1990 Optical Society of America