Defect Complexes in Highly Mg-Doped GaN Studied by Raman Spectroscopy

We report on local vibrational modes (LVMs) in highly Mg-doped GaN grown by molecular beam epitaxy. Two groups of LVMs in the region of GaN host phonons and in the vicinity of 2200 cm ± 1 are observed. We performed temperature-dependent Raman-scattering experiments and annealing experiments to investigate the defect complexes which are the origin of the high-energy LVMs. The temperature-dependent measurements show an unexpected hardening of the two most intense LVMs at 2166 and 2185 cm ± 1. Furthermore, we found that all high-energy modes disappeared after annealing at 1065 C. The experimental results are discussed in terms of existing theoretical models. 1