Study of ideal vacancies in CdS (wurtzite)

The electronic states of ideal vacancies of Cd and S in the CdS lattice with the wurtzite structure are calculated with the use of a Green's-function method. The electronic band structure is computed within a tight-binding approximation by fitting the pseudopotential energy bands obtained by Bergstresser and Cohen. When interactions up to second neighbors are taken into account, both valence and conduction bands are accurately reproduced. We show that cation vacancies may induce bound states inside the fundamental gap while anion vacancies induce bound states in the gap between the conduction $s$ and $p$ cationic states.