Vibrational properties of cubic AlxGa1-xN and InxGa1-xN ternary alloys

The phonon dispersion curves and phonon density of states of the cubic AlxGa1-xN and InGa1-xN alloys were calculated within the framework of a valence force field method and an effective charge approach for the long-range Coulomb interaction. The valence-force parameters and effective charges for the cubic GaN, AlN and InN binary compounds were fitted to the phonon frequencies at high-symmetry points in the Brillouin zone measured by Raman spectroscopy an, calculated by ab initio methods. The scaling factor approximation was used to obtain the valence force parameters and effective charges for the alloys. A good agreement between our calculation and recent Raman data for the alloys is achieved.