Reflectance spectra of $p$-Bi$_{2}$Te$_{3}$ : Sn crystals in a wide IR region

The reflectance spectra of a $p$-Bi$_{2}$Te$_{3}$ : Sn crystal are recorded in the range 50–7900 cm$^{-1}$. The spectra possess features characteristic of charge-carrier plasma oscillations and a contribution of phonons. It is shown that the dielectric function that is used in the context of Drude–Lorentz theory and includes the contributions of hole plasma oscillations and two phonons adequately describes the experimental data obtained at room temperature and at a temperature of $T$ = 78 K.