Migration of carbon from Ga sites to N sites in GaN: A combined PAS and hybrid DFT study

Carbon (C) is of great importance to realize semi-insulating gallium nitride (GaN) for power electronic devices. We demonstrate that C can migrate from Ga sites to N sites after high temperature annealing of C doped GaN. The migration process is revealed through the observation of the generated Ga vacancies-related defects after annealing by positron annihilation spectroscopy. The activation energy of this migration process is estimated to be 2.5-2.8 eV from the temperature dependent annealing experiments, which is well consistent with the theoretical results from first-principles calculations.