Efficient non-vertical interband transitions in porous silicon

In this work, we study an inhomogeneous material, porous silicon (PS), using a supercell model and an s p3 s* tight-binding Hamiltonian. The interband non-vertical transitions are studied in two schemes, which consider different contributions within the intra-atomic approximation. The oscillator strength analysis as a function of the porosity reveals a significant enlargement of the optically active zone in the k-space, due to the localization of the wave function.