Electronic structure of Cu, Ni, Co, and Fe substitutional impurities in gallium arsenide

We have calculated the electronic structure of neutral copper, nickel, cobalt, and iron impurities replacing gallium atoms in the gallium-arsenide lattice using the $X\alpha$ scattered-wave method. Clusters of 17 atoms in a tetrahedral configuration are used to simulate the bulk and the locally perturbed crystal. The calculations were carried out to self-consistency and in the spin-polarized limit. The results indicate that the impurities studied yield acceptor energy levels deep in the crystal fundamental band gap, in agreement with experiment. The role played by the metal $d$ states in the formation of the impurity centers is discussed and compared with the available experimental data.