A novel activation process for Mg-implanted GaN was demonstrated. As opposed to the conventional thermal annealing process, an H-2/NH3 alternating supply annealing process achieved better optical activation, stronger near-ullraviolel luminescence and weaker yellow luminescence in the phololuminescence spectroscopy. After this process, small hexagonal hillocks were observed on the surface, which indicated that crystal regrowth was induced by this process, consisting of decomposition of GaN by H-2 supplies and re-crystallization by NH3 supplies. It was revealed that the implanted Mg could easily be located at the activation site by means of crystal regrowth by this process. (C) 2013 Elsevier B.V. All rights reserved