Abstract:
The spectral dependences of the absorption coefficient $\alpha$ in a submicron samples of the $n$-Bi$_2$Te$_3$+CdBr$_2$ topological insulator, which have optimal thermoelectric properties at high values of the Seebeck coefficient at temperatures below room temperature, are studied at temperatures of 205 and 300 K. The components of optical absorption spectra associated with interband and intersubband electron transitions are revealed and analyzed. It was found that in bismuth telluride, with decreasing temperature, the optical transition of electrons at the interband absortion threshold remain direct and allowed. The values of energy gaps between the absolute extrema of the conduction and valence bands, as well as between the main and additional subbands of conduction band, are estimated. It is shown that the rates of their change with temperature are opposite in sign. The energy band diagram of Bi$_2$Te$_3$ is constructed, which corresponds to experimental data.
Keywords:bismuth telluride, topological insulator, optical absorption, interband and intersubband optical transitions, energy band diagram.
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