Effect of nonuniform continuum density of states on a Fano resonance in semiconductor quantum wells

Abstract

We experimentally study the excitonic Fano resonance in GaAs/Al0.3Ga0.7As multiple quantum wells under an external electric field. The resonance results from exciton transitions via localized states and continuum minibands of Wannier-Stark states. In photoreflectance spectra the line shape displays anomalous behavior as a function of increasing field. Our theoretical analysis reveals that this effect, which is absent for the conventional Fano resonance, arises from the field dependence of the nonuniform density of continuum states.