Temperature Modulation of the Optical Constants of Layer Compounds GaSe and GaS

Abstract
We report the thermoreflectance spectra of the layer compounds GaSe and GaS at liquid-nitrogen temperature in the energy interval 2-6 eV. The spectra were subjected to a Kramers-Kronig analysis, and the changes in the real and imaginary parts of the dielectric constant, induced by the temperature change of the samples, were obtained. The optical constants of the two materials were computed by processing the known reflectivity spectra. A phenomenological interpretation of the observed experimental results is presented. It is shown that under certain conditions it is necessary to invoke the presence of excitons at saddle-point singularities in order to achieve reasonable agreement between theory and experiment.

This publication has 19 references indexed in Scilit: