Atomic and electronic properties of anion vacancies on the (110) surfaces of InP, InAs, and InSb

We have performed total-energy density-functional calculations using first-principles pseudopotentials to determine the atomic and the electronic structure of the anion vacancy on the (110) surfaces of InP, InAs, and InSb. An inward relaxation of the three neighboring In atoms next to the anion vacancy is obtained, but the stable atomic structure depends critically on the vacancy charge state. The +1 charged vacancy exhibits a nonsymmetric configuration with one rebonded dimer, while both 0 and -1 charged vacancies show a symmetric configuration with loosely rebonded and rebonded trimer, respectively. For InP and InAs, the charge-transfer levels ε(+1/0) and ε(0/-1) are located around the center of the band gap; whereas for InSb, the -1 charge state is stable in the whole band gap. In contrast to bulk, the surface vacancy is a positive-U center. The band structures and the density of states have been calculated. Three vacancy states, one deep in the valence band and two around the band gap, are identified. Our results show that the character of the vacancy states is mainly dependent on the atomic configuration.