Some parameters of band structure in copper selenide and telluride

The reflection spectra of p-type copper selenide and telluride have been studied in the region 0.8 to 8 μm. The carrier effective masses were calculated by the position of the plasma minimum as a function of concentration and temperature. It is found that m in copper selenide decreases with increasing concentration and that m in copper selenide and telluride increases with the temperature from 0.16 me at 100°K to 0.9 me at 450°K and from 0.50 me at 100°K to 0.85 me at 640°K, respectively. The observed increase in the effective masses may be caused, first, by the complex structure of the valance bands and secondly by polymeric transformations at high temperatures.