Piezoelectric-field-induced localization of barrier states in {211}-oriented InAs/GaAs superlattices

We observe localized states whose energy is resonant with the continuum in GaAs with periodically inserted {211}-InAs sheets. Evidence for these states comprises excitonic interband transitions above the gap of GaAs, observed by piezoreflectance and photoluminescence-excitation spectroscopies. This localization has its origin in the strain-induced electric field existing in the InAs layers, which we show by simulations of the dielectric function based on envelope-function-type calculations.