The diffusion properties of fluorine ions in GaN were investigated by means of time-of-flight secondary ion mass spectroscopy. Instead of incorporating fluorine ions close to the sample surface using plasma, fluorine ion implantation with an energy of 180keV was used to implant ions deep into the GaN bulk; preventing surface effects from affecting the data analysis. It was found that the diffusion of fluorine ions was a dynamic process, involving a two-step process. A defect-assisted diffusion model was used to explain the experimental observations. Fluorine ions tended to occupy Ga vacancies induced by fluorine ion implantation and diffuse to vacancy-rich regions. The ions became stable after continuous vacancy chains were significantly reduced or removed by thermal annealing.

Study of Diffusion and Thermal Stability of Fluorine Ions in GaN by Time-of-Flight Secondary Ion Mass Spectroscopy. M.Wang, L.Yuan, F.Xu, B.Shen, K.J.Chen: Physica Status Solidi C, 2009, 6[S2], S952-5