Effects of Cu addition on band gap energy, density of state effective mass and charge transport properties in Bi2Te3 composites

Abstract

We report the effects of Cu addition on the charge transport properties in n-type Cu_xBi₂Te₃ composites. The conducting behavior of the composites changed from metallic to semiconducting character with the increase in the amount of Cu, and its origin was found to be the decrease in the electron concentration by the substitution of Bi with Cu. Hall mobilities in the Cu-substituted composites were significantly enhanced due to the alleviated ionized impurity scattering, however, they were governed dominantly by electron–acoustic phonon scattering at relatively high temperature. As well as the carrier concentration and mobility, the electronic structure of Bi₂Te₃ was also affected by the Cu addition, and it was manifested by both the increase in the band gap (∼198 meV in Cu_0.04Bi₂Te₃) and the reduction in the density of state effective mass in the Cu-substituted Bi₂Te₃ composites.