Phosphorus vacancy in InP: A negative- U center

Abstract

Using first-principles simulations, we identify the phosphorous vacancy in InP as a negative-U center. The deep levels associated with this defect are in the upper half of the band gap, and the charge state changes directly from positive to negative as the Fermi level is raised: the vacancy captures two electrons rather than one. We also obtain the relaxed structures and formation energies for the In and P vacancies as a function of both electron and atomic chemical potentials.