Electronic structure of copper, silver, and gold impurities in silicon

The electronic structure of Cu, Ag, and Au impurities in silicon is studied self-consistently using the quasiband crystal-field Green’s-function method. We find that a substitutional model results in a two-level (acceptor and donor), three-charge-state ($A^{+}$, $A^0$, and $A^{\mathrm{-}}$) system, which suggests that these defects are amphoteric. Our results show that these substitutional impurities form e-type and $t_2$-type crystal-field resonances (CFR) near the center of the valence band and a dangling-bond hybrid (DBH) $t_2$ level in the gap. The $e^{\mathrm{CFR}}$ and $t_2^{\mathrm{CFR}}$ states are fully occupied and represent the perturbed and hybridized impurity atomic orbitals (not simply a ‘‘$d^{10}$’’ configuration). They are magnetically and electrically inactive but are predicted to be optically active in the uv, producing both impurity-bound core excitons as well as localized-to-itinerant