A theoretical study of the vibrational properties of In/sub x/Ga/sub 1-x/As/sub 1-y/Sb/sub y/ quaternary alloys

First theoretical investigations of the lattice dynamics of In/sub x/Ga/sub 1-x/As/sub 1-y/Sb/sub y/ quaternary semiconducting alloys are presented. All corresponding pseudobinary end member components are known to exhibit mixed-mode behaviour. Within a mean-field approximation a Bethe lattice is self-consistently constructed in such a way that for all mixed ternary end member compounds the results of the coherent-potential approximation (CPA) are reproduced. Special results are obtained for the dielectric susceptibility spectra, which display only one dominant band for mixed quaternaries mainly containing GaAs but two bands for systems which contain mainly InSb. With respect to an interchange between x and y the lineshape of the spectra is nearly unchanged. (author)