In-plane anisotropy of the optical properties of ${(\mathrm{I}\mathrm{n}}_{0.5}{\mathrm{Ga}}_{0.5}\mathrm{As}{)}_n/(\mathrm{InP}{)}_n$ superlattices

In this paper we study the electronic and optical properties of $({\mathrm{In}}_{0.5}{\mathrm{Ga}}_{0.5}\mathrm{As}{)}_n/(\mathrm{InP}{)}_n$ superlattices, where the ${\mathrm{Ga}}_{0.5}{\mathrm{In}}_{0.5}\mathrm{As}$ alloy is described both through the virtual crystal approximation (VCA) and through an appropriate ordered ternary structure. By first-principles calculations of the dielectric tensor elements we address the issue of the giant polarization anisotropy of the optical absorption experimentally observed in these superlattices. The magnitude of the anisotropy depends on the splitting between the hole states at the valence band top which is due to the lowering of the overall symmetry to the $C_{2v}$ point group and it is greatly influenced by strain not only at the interfaces but also in the bulk alloy.