Effects of interface-roughness scattering on resonant tunneling

We calculate the effects of interface-roughness scattering on the current-voltage characteristics of a GaAs-${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As double-barrier structure. We treat this scattering within the coherent-potential approximation so that the theory is nonperturbative and preserves unitarity. The scattering does not change the peak current significantly, even though the electrons are scattered many times while in the quantum well. The valley current, on the other hand, increases by several orders of magnitude in a structure with thick barriers. In good qualitative agreement with recent experiments we find that the peak-to-valley ratio grows only very slowly with barrier thickness for barriers thicker than ≊100 Å.