The mechanism of charge transfer in Bi2(Te0.9Se0.1)3 solid solution thin films

The conductivity, Hall effect, and magnetoresistance of Bi-2(Te0.9Se0.1)(3) solid solution thin films are studied in a wide temperature range from 2.5 to 300 K and in high magnetic fields of up to 8 T. It is found that the conductivity of Bi-2(Te0.9Se0.1)(3) solid solution thin films is of the insulator type, whereas the conductivity of the corresponding bulk single crystals is of metallic type. It is inferred that, at high temperatures (100-300 K), the conductivity is controlled mainly by thermally activated charge-carrier transport over extended states in the conduction band, with an activation energy of about 15 meV. At lower temperatures (2.5-70 K), conductivity controlled by charge-carrier hopping between localized states in a narrow energy region close to the Fermi level is dominant. From the magnetoresistance and conductivity data, the localization radius, the density of localized states, and the average charge-carrier hopping length are estimated.