Energy gaps and optical phonon frequencies in InP1-xSbx

We present a theoretical investigation of the energy band-gaps and vibrational properties of InP1-xSbx semiconducting alloys in the zinc-blende structure. For this purpose a pseudopotential scheme within the virtual crystal approximation that takes into account the effects of compositional disorder, combined with the Harrison bond orbital model are used. In general, our results are in good agreement with the available experimental values to within a few per cent. The absorption at the optical gaps indicates that the material of interest is a direct F to F band-gap semiconductor for the whole range of the Sb content. It is found that both the fundamental band-gap and the optical phonon frequencies change non-linearly with varying the composition x. The information derived from the present study predicts that InP1-xSbx properties cross very important technological infrared and mid-infrared spectral regions.