Band structure and absorption properties of GaAs1-xNx/InAs1-yNy short period superlattices strained to InP (001)

The k center dot p approximation and the band anticrossing model modified for the strain are used to describe the electronic states of the strained bulk GaAs1-xNx and InAs1-yNy ternaries in the vicinity of the center of the Brillouin zone (Gamma point) and their respective band offsets have been evaluated, before implementing them into the superlattice structure. By minimizing the total mechanical energy of the stack of the alternating layers of GaAs1-xNx and InAs1-yNy in the superlattice, the ratio of the thicknesses of the epilayers is determined to make the structure lattice matching on InP(001). Energy miniband structure of the superlattice is then investigated using the transfer-matrix formalism, predicting the evolution of the band-edge transition energies for different nitrogen concentrations and thickness combinations. The results show the potential to significantly reduce the band gap compared to quaternary alloys of similar average concentration and to obtain photon absorption and emission energies in the range of 0.65-0.35 eV at 300 K for a typical nitrogen concentration of <= 5%. Finally, the optical-absorption coefficient of such a superlattice, as a function of the nitrogen concentration, the change in electron effective masses, and the temperature are estimated under the anisotropic medium approximation.