Investigations on the local structure and the EPR parameters for Cu2+-doped GaN

摘要

The local structure and the EPR parameters (g factors and the hyperfine structure constants) for Cu2+ in GaN are theoretically studied from the perturbation formulas of these parameters for a 3d(9) ion in trigonally distorted tetrahedra. In these formulas, the ligand orbital and spin-orbit coupling contributions are taken into account from the cluster approach, in view of the strong covalency effect of the system. Based on the studies, the impurity Cu2+ is found not to occupy exactly the host Ga3+ site but to suffer a slight displacement (approximate to 0.004 angstrom) towards the ligand triangle along C-3 axis due to charge and size mismatching substitution. The theoretical EPR parameters show good agreement with the experimental data. The validity of the impurity displacement is also discussed.