On the influence of a smooth gaussian random field on optical thresholds in disordered semiconductors and external electric field induced change

The interband dielectric function ϵ(ω) and its external field induced change Δϵ(ω, E ) are calculated in the one‐electron approximation for optical transitions between initial and final states shifted randomly in space by a smooth Gaussian random field. All types of critical points are considered. Using an exact semi‐classical approach up to the order of h 2 the influence of the smooth Gaussian random field in ϵ(ω) and Δϵ(ω, E ) is shown to be representable as an averaging of the corresponding Franz‐Keldysh expressions. The M 3 and M 2 problems are shown to be reducible to the M 0 and M 1 ones. The plots for ϵ(ω) and Δϵ(ω. E ) are presented for the isotropic M 0 point and the M 1 point with equal transversal masses.