In this study, we investigated the 248 nm excimer-laser-induced activation of the Mg-doped GaN layers. According to the observed photoluminescence results and the x-ray photoelectron spectroscopy measurements, we found that the dissociation of the Mg–H complexes and the formation of hydrogenated Ga vacancies (i.e., VGaH2) and/or the Ga vacancies occupied by interstitial Mg during the laser irradiation process, led to an increase in the hole concentration.