Stark Localization in GaAs-GaAlAs Superlattices under an Electric Field

We have observed that a strong electric field E shifts to higher energies the photoluminescence and photocurrent peaks of a GaAs-Ga0.65{Al}0.35$As superlattice of period $D$ (=65 {}), 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 [{}(2-3)×{}10⁴ V/cm], the coupling between adjacent wells is manifested by four additional peaks that shift at the rates ±eED and ±2eED and correspond to transitions that involve different levels of the Stark ladder.