Ab-initio investigation of the polarization anisotropy of the optical absorption in (InGa)As-InP superlattices

In this paper we present a theory which accounts for both the intensity and the shape of the experimentally observed giant polarization anisotropy of the optical absorption in (InGa)As-InP superlattices. By first-principles s elf-consistent calculations of the superlattice crystal potential and of th e dielectric tensor elements we derive a "selection rule'' by which the rad iation polarization along the 110 and -110 directions choose only one optic al transition of the doublet corresponding to transitions to the conduction band from the two upper crystal field split hole states which are degenera te in common atom superlattices. However, due to the similar intensity of t he oscillator strength of these transitions, it turns out that the magnitud e of the anisotropy depends only on the magnitude of the energy gap between the split states.