On the conduction-band structure of bismuth telluride: optical absorption data

The optical absorption spectra of n-Bi₂Te₃ in the range 40–300 meV are studied at room temperature in relation to the electron concentration and sample thickness in order to determine the parameters of the additional subband in the conduction band of Bi₂Te₃ and to clarify the possible effect of this subband on charge-carrier transport. It is shown that bismuth telluride is a direct-gap semiconductor with an additional subband in the conduction band. These data are consistent with the results of studies of quantum oscillations in n-Bi₂Te₃ in high magnetic fields at temperatures below 20 K.