Site occupation and electronic structure of an interstitial Mn2+impurity in GaP

The site occupation and electronic structure of an interstitial Mn2+ impurity in GaP are studied using the discrete-variational local-spin-density-functional method with cluster models. The results verify the conjecture of van Gisbergen et al. that the Mn2+ impurity prefers the interstitial site surrounded by four nearest-neighbour Ga atoms and show that a small host crystal relaxation and a large formation energy of the impurity measured with respect to GaP and Mn2+ occur. Two deep donor levels are found in the host crystal band gap owing to the presence of the impurity. The behaviour of the impurity is analysed and compared with results of the EPR experiment.