Native defects in second-generation topological insulators: Effect of spin-orbit interaction on Bi2Se3

Native defects in pnictogen chalcogenides are currently a great barrier toward the realization of the exotic properties of this class of topological insulators. Previous first-principles results of low-energy defects in Bi${}_{2}$Te${}_{3}$ and Sb${}_{2}$Te${}_{3}$ are in qualitative agreement with experiments. However, for Bi${}_{2}$Se${}_{3}$ the calculated low-energy defects are antisites, opposed to the Se vacancy (${V}_{\mathrm{Se}}$) as observed experimentally. We find that the inclusion of spin-orbit interaction drastically shifts the band-edge energies of the bulk states with respect to defect transition energies. It turns the Bi antisite (Bi${}_{\mathrm{Se}}$) from an acceptor to a donor and makes ${V}_{\mathrm{Se}}$ more stable than Bi${}_{\mathrm{Se}}$. This brings the calculated results for native defects in pnictogen chalcogenides into agreement with experiments.