First-principles density functional theory study of native point defects in Bi2Te3

We present a first-principles study of the native point defects in the thermoelectric material Bi2Te3. Calculated formation energies of defects and electronic densities of states were analyzed in detail. The most prominent native point defects considered are vacancies and antisite defects on the Bi, Te1, and Te2 sublattices of the Bi2Te3 structure. Vacancies on all three sublattices are found to have much higher formation energies than antisite defects. The most dominant antisite defects are found to be Bi-Te1 at Bi-rich conditions, and Te-Bi at Te-rich conditions. These lead to the formation of resonant defect states at the top of the valence band and bottom of the conduction band, respectively. Hence they are expected to impact charge and energy transport in a profound way. Furthermore antisite defect pairs tend to form at nearest-neighbor distances, and lead to substantial changes in the electronic structure and hence in the thermoelectric properties of Bi2Te3.