Small hole polaron in CdTe: Cd-vacancy revisited

The characteristics of electronic states of Cd-vacancies in CdTe, an important semiconductor for various technological applications, are under debate both from theoretical and experimental points of view. Experimentally, the Cd-vacancy in its negative charge state is found to have C-3v symmetry and a (-1/-2) transition level at 0.4 eV. Our first principles density functional calculations with hybrid functionals confirm for the first time these experimental findings. Additionally, we find that the C-3v symmetry and the position of the (-1/-2) transition level are caused by the formation of a hole polaron localised at an anionic site around the vacancy.