Electronic structure of transition-metal impurities in semiconductors: Cu in GaP

A numerical method for calculation of the electronic structure of transition metal impurities in semiconductors based on the Green function technique is developed. The electronic structure of 3d impurity is calculated within the LDA+U (local density approximation with interaction) version of density functional method, whereas the host electron Green function is calculated by using the linearized augmented plane wave expansion. The method is applied to the Cu impurity in GaP. The results of calculations are compared to those obtained within the supercell local density approximation procedure. It is shown that in the Green function approach Cu impurity has an unfilled 3d shell. This result paves a way to explanation of the magnetic order in dilute Ga(1-x)Cu(x)P alloys.