Formation processes and annealing of defects in gamma-irradiated n-GaN are investigated for the first time using electrical measurements and Raman spectroscopy. The production rate of defects turned out to be dependent on the dopant concentration. This suggests that at least one kind of native defect is involved in impurity-defect interactions. Two prominent stages of defect annealing are revealed. The annealing processes at T greater than or equal to 100 degrees C are associated with mobile native defects. A considerable fraction of radiation defects is still present in the material after an annealing step at T greater than or equal to 750 degrees C.