<i>First-principles calculations of copper vacancy centers in zinc sulfide</i>

Transition metal impurities and impurity-vacancy systems in wide-gap semiconductors provide a robust platform for realizing optoelectronic applications and a coherent, room-temperature interface between spins and photons. Here we calculate the electronic and structural properties of copper-vacancy complexes in zinc sulfide (ZnS) within the density functional theory. We fix the well-known band-gap problem using the hybrid functionals and calculate a band gap, which agrees excellently with the experimental value. Zinc is then substitutionally replaced with a copper atom, and the vacancy is formed at one of the neighboring sulfur atoms. We perform the ionic relaxations and calculate the defect formation energies for different charged states. The charge transition levels are also computed from the relaxed final energies, including supercell corrections due to finite-size effects. Finally, we calculate the density of states, orbital projected densities, and electronic band structures of the system to identify states located in the bandgap and determine the characteristics of the system. We show that ZnS with Cu-vacancies could be a promising system in which impurity spin and light interaction can be realized.