Li impurity in ZnSe: Electronic structure and the stability of the acceptor

We have performed density-functional calculations of a Li impurity in ZnSe using the dynamical simulated-annealing scheme with the supercell method. We find that Li at a substitutional Zn site has a higher free energy than the sum of those of a Zn vacancy and interstitial Li when the chemical potential is located below 0.8 eV measured from the valence-band maximum. The calculated result shows that, in the case of the substitutional Li impurity, there occurs an inward breathing relaxation and a Jahn-Teller distortion around the impurity site. It is also found that the interstitial Li acts as a shallow donor with small lattice relaxation (0.1 {}).