Wannier-Stark localization ofXand Γ states in GaAs-AlAs short-period superlattices

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Abstract
We report the observation of Wannier-Stark localization effects for both X- and Γ-derived miniband states in GaAs-AlAs superlattices in an axial electric field. The splitting of the optical interband transitions into Stark ladders is observed in both photoconductivity and photoluminescence. The behavior of the light-mass Γ states is interpreted with use of a new theoretical model for the superlattice exciton states in an axial electric field. We show that for the small Γ-X separations in the structures considered it is necessary to include the effects of Γ-X mixing in order to understand the behavior of the X states.