Small hole polaron in CdTe: Cd-vacancy revisited

Abstract

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 C3v 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 C3v 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.

Characterization of point defects in CdTe by positron annihilation spectroscopy

“…There is evidence that the stable charge states of the Cd vacancy are negative. 1, 3 The reduction in s m with reducing temperature observed in Fig. 1 has also been observed for Cl-doped and In-doped CdTe.…”

“…27,30 Recent firstprinciples calculations of point defects in CdTe have provided further insight on local structure and stability. [1][2][3][4][5]31 Possible relaxed geometries of the two stable charge states, À1 and À2, of the Cd vacancy, 1,3 and for the À1 charge state of Cl-donor A-center, V Cd with a Cl Te nearest neighbor, 2 have been reported. The other point defect considered of particular importance in these materials is the Te antisite; this has also been studied and relaxed structures for the three charge states, Te þ2…”

“…15,27 For the À1 state of V Cd , two possible electronic configurations were considered, the symmetric T d symmetry state and the more stable polaronic C 3v state. 3 The C 3v state can be considered by assuming the polaron is localized on the "top" Te ion, Te-1 in Fig. 2(a), the separation between the vacant Cd site and Te-1 decreases by 2.9% and the separation between the from the Cd vacancy site to the lower three Te ions reduces by 9.2%.…”

“…2(a), the separation between the vacant Cd site and Te-1 decreases by 2.9% and the separation between the from the Cd vacancy site to the lower three Te ions reduces by 9.2%. 3 (Table I).…”

Adsorption Study of a Water Molecule on Vacancy-Defected Nonpolar CdS Surfaces

“…On inclusion of more accurate theoretical treatments, like hybrid functionals, 17,18 occupation-dependent potentials, 19 and other self-interaction schemes, 20 it is seen that the coupling strength of such magnetic vacancies is too weak to explain the experimentally observed FM ordering. It is because they observed that the holes are more localized at the defect sites than predicted by the local and semilocal functionals.…”