Anisotropy of the Electrical Conductivity in Bismuth Telluride

Abstract

The anisotropy of the electrical conductivity of Bi₂Te₃ at room temperature has been determined by a four-probe method. The anisotropy ratio for undoped p-type material is close to 3.0; for iodine-doped n-type material it is appreciably higher and increases with the impurity concentration. Measurements of the galvanomagnetic effects in highly doped n-type Bi₂Te₃ have shown that the observed variation of the anisotropy ratio can be interpreted in terms of a change of shape of the equi-energy surfaces in momentum space with increasing density of charge carriers.