Indirect-direct anticrossing in GaAs-AlAs superlattices induced by an electric field: Evidence of Γ<i>-</i>X mixing

Abstract

We demonstrate that a GaAs-AlAs superlattice can be switched from indirect to direct, in both real and reciprocal spaces, by application of a modest axial electric field. The crossover region is found to be an anticrossing, manifesting the presence of \ensuremath{\Gamma}-X mixing by a potential measured to be of the order of 1 meV. This value is corroborated by time-decay measurements performed on different superlattices.