Exciton Thermoabsorption of GaSe 1− x S x Solid Solutions

Results are reported obtained at liquid nitrogen temperature by thermally modulating the absorption of GaSe 1− x S x solid solutions. In order to clarify the relations among different polytypes, their optical properties, and growth methods, a complete series of measurements is performed, varying the compositional parameter x from 0 to 1, for single crystals grown both from the vapour and from the melt. The results are consistent with the existence of a unique polytype (ε) for x ≈ 0 in crystals grown by both methods. Discontinuities in the exciton ground state energy E 0 versus x curves are related to interpolytype transitions, namely γ → β andε → β, for melt‐ and vapour‐grown crystals, respectively.