The amorphous gallium nitride thin films doped with Mn were deposited by laser assisted molecular beam epitaxy. After annealing at different NH3 flow rates, the high-quality GaMnN crystalline films with different concentration of nitrogen vacancies (VN) were obtained, which were confirmed by the X-ray diffraction spectroscopy and Raman measurements. The magnetic behaviors of these films were also obtained to investigate the effects of nitrogen vacancies. It indicates that VN play a significant role in the origin of ferromagnetism. The stronger room-temperature ferromagnetism was given with the higher VN concentration when it was not beyond a critical concentration. Moreover, from the M(T) curves and Raman analysis, the films were deduced to have a  high resistivity. The magnetism of films with high resistivity varies with concentration of nitrogen vacancies, which can be explained by the bound magnetic polaron theory.

Nitrogen Vacancy Effects on the Ferromagnetism of Mn Doped GaN Films. B.Hu, B.Y.Man, M.Liu, C.Yang, C.S.Chen, X.G.Gao, S.C.Xu, C.C.Wang, Z.C.Sun: Applied Physics A, 2012, 108[2], 409-13