Atomic-scale modeling of interface roughness scattering in quantum cascade lasers

The theory of interface roughness scattering is well established in the case of idealized abrupt interfaces. Here we generalize this theory for finite interfacial widths. Experimental findings for Ge/GeSi interfaces show that the interface roughness can be correlated along the growth directions at length scales smaller than the interfacial width. This feature is included in a generalized theory of interface roughness scattering, accounting for correlations along both in-plane and out-of-plane directions. This model is included in a nonequilibrium Green’s functions simulator, allowing to assess the impact of interface roughness on the performances of quantum cascade lasers.