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 by plasma, fluorine ion implantation with an energy of 180keV was utilized to implant fluorine ions deep into the GaN bulk, preventing the surface effects from affecting the data analysis. It was found that the diffusion of fluorine-ions in GaN was a dynamic process, featuring a two-step process. A defect-assisted diffusion model was proposed to account for the experimental observations. Fluorine ions tend to occupy Ga vacancies induced by fluorine ion implantation and diffuse to vacancy rich regions. The fluorine ions become 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