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 phono ns and in the vicinity of 2200 cm(-1) are observed. We performed temperatur e-dependent Raman-scattering experiments and annealing experiments to inves tigate the defect complexes which are the origin of the high-energy LVMs. T he temperature-dependent measurements show an unexpected hardening of the t wo most intense LVMs at 2166 and 2185 cm(-1). Furthermore, we found that al l high-energy modes disappeared after annealing at 1065 degrees C. The expe rimental results are discussed in terms of existing theoretical models.