C-implantation N-polar GaN films are grown on c-plane sapphire substrates by metal organic chemical vapor deposition.C-implantation induces a large number of defects and causes disorder of the lattice structure in the N-polar GaN film.Raman measurements performed on the N-polar GaN film before C-implantation after C-implantation and subsequent annealing at 1050℃ for 5min indicate that after annealing the disordered GaN lattice is almost recovered.High resolution x-ray diffraction shows that after implantation there is an obvious increase of screw-dislocation densities,and the densities of edge dislocation show slight change.Carbon implantation can induce deep acceptors in GaN,thus the background carriers induced by the high oxygen incorporation in the N-polar GaN film will be partially compensated for,resulting in 25 times the resistivity,which is demonstrated by the temperature-dependent Hall-effect measurement. C-implantation N-polar GaN films are grown on c-plane sapphire substrates by metal organic chemical vapor deposition. C-implantation induces a large number of defects and causes disorder of the lattice structure in the N-polar GaN film. Raman measurements performed on the N-polar GaN film before C-implantation after C-implantation and subsequent annealing at 1050 ° C for 5 min indicate that after annealing the disordered GaN lattice is almost recovered. High resolution x-ray diffraction shows that after implantation there is an obvious increase of screw-dislocation densities, and the densities of edge dislocation show slight change. Carbon implantation can induce deep acceptors in GaN, thus the background carriers induced by the high oxygen incorporation in the N-polar GaN film will be partially compensated for, resulting in 25 times the resistivity, which is demonstrated by the temperature-dependent Hall-effect measurement.