Stark Localization in GaAs-GaAlAs Superlattices under an Electric Field

Abstract

We have observed that a strong electric field $\cal E$ shifts to higher energies the photoluminescence and photocurrent peaks of a GaAs-Ga${0.65}$Al${0.35}$As superlattice of period $D$ (=65 Å), which we explain by a field-induced localization of carriers to isolated quantum wells. Good agreement is found between observed and calculated shifts when the large field-induced increase of the exciton binding energy is taken into account. At moderate fields [$\approx$ (2–3) $\times 10^4$ V/cm], the coupling between adjacent wells is manifested by four additional peaks that shift at the rates $\pm e {\cal E} D$ and $\pm 2 e {\cal E} D$ and correspond to transitions that involve different levels of the Stark ladder.