On the band structure of Bi$_{2}$Te$_{3}$

For $p$-Bi$_{2}$Te$_{3}$ crystals grown by the Czochralski method, the temperature dependences of the conductivity, Hall coefficient, thermoelectric power ($\alpha$), and transverse Nernst–Ettingshausen coefficient are obtained experimentally in the temperature range 77–450 K. The transmittance spectrum in the range 400–5250 cm$^{-1}$ is recorded at room temperature. It is shown that, to interpret the temperature dependences of the scattering parameter r and the ratio of the thermoelectric power to temperature $(\alpha/T)$, it is essential to take into account the complex valence-band structure and the contribution of heavy holes to transport phenomena. Estimations of the energy band parameters in the context of the two-band model give a hole effective mass close to the free electron mass and the energy gap between nonequivalent extrema at a level of several hundredths of eV. In the absorption spectrum derived from the transmittance spectrum, a sharp increase in absorption defined by indirect interband transitions with the band gap $E_g\approx$ 0.14 eV is observed in the region of frequencies $\nu\ge$ 1000 cm$^{-1}$. The absorption spectrum calculated from the reflectance data using the Kramers–Kronig relations is in agreement with the experimental absorption spectrum.