Ar+ ions were implanted at room temperature in n-type hexagonal GaN for device isolation purpose. We performed electrical measurements and resonance Raman spectroscopy in order to monitor the electrical and structural changes of non-annealed and annealed implanted GaN samples. On increasing the implantation dose from 3.4 × 1012 to 3.4 × 1014 ions cm−2, an increase in the electrical isolation and a decrease in the photoluminescence were observed. For a 1016 ions cm−2 dose, the implanted layer became conductive owing to a hopping mechanism and only the first-order phonon lines remained observable. After annealing at 900 °C for 30 s, the implanted samples became conductive and the photoluminescence reappeared or increased compared with the non-annealed samples at same implantation doses, except for the sample implanted at the highest dose, which became insulating.