Abstract:
The infrared reflection and transmission spectra of Bi$_2$Te$_2$Se single crystals grown by the modified Bridgeman method have been studied in the spectral range of $30$–$10000$ cm$^{-1}$ at temperatures of $5$–$300$ K. The bandgap and its temperature dependence, optical function spectra, and concentration of free charge carriers in Bi$_2$Te$_2$Se have been determined.