Second-Order Raman Spectra and Phonon Dispersion in GaP

Abstract

The second-order Raman spectrum of GaP has been investigated experimentally. The experiments were performed on oriented single crystals at both 300 and 77 °K. A critical point analysis of the data has been carried out with the aid of the polarization selection rules. The resulting frequencies are also consistent with a theoretical model which in turn is used to calculate the phonon dispersion throughout the Brillouin zone. The one- and two-phonon density of states and the specific heat have also been calculated and compared to our spectra and available specific heat data. The calculated quantities have also been compared to similar quantities obtained from neutron scattering experiments. This comparison provides information on the accuracy and reliability of phonon dispersion curves obtained from Raman scattering experiments.