Splittings and correlations between the long-wavelength optical phonons in the layer compounds GaSe, GaTe, andGaSe1−xTex

Abstract

The zone-center optical phonons of layer materials GaSe, GaTe, and their solid solutions are studied by means of Raman scattering. Most of the structure in the hitherto unstudied spectrum of GaTe is identified by following their evolution in the solid solutions and relating them to already known bands in GaSe. Increased layer-layer interaction, as solutions become richer in Te, allow the observation of Davydov splittings. Detailed study of the spectra of $\mathrm{Ga}{\mathrm{Se}}_{1-x}{\mathrm{Te}}_x$ reveal an abrupt phase transition from hexagonal to monoclinic structures in the composition range $0.26<x<\mathrm{}0.60\mathrm{}$. Both one- and two-mode behaviors are observed in the phonon bands of the solid solutions.