The diffusion mechanisms of fluorine ions in GaN were investigated by means of

time-of-flight secondary ion mass spectrometry. Instead of incorporating fluorine

ions close to the sample surface by fluorine plasma treatment, 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 an initial out-diffusion followed by in- diffusion and the final

stabilization. A vacancy-assisted diffusion model was proposed to account for the

experimental observations, which was also consistent with results on molecular

dynamic simulation. Fluorine ions tend to occupy Ga vacancies induced by ion implantation and diffuse to vacancy rich regions. The number of continuous

vacancy chains can be significantly reduced by a dynamic thermal annealing

process. As a result, strong local confinement and stabilization of fluorine ions can

be obtained in GaN crystal, suggesting excellent thermal stability of fluorine ions

for device applications.

Diffusion Mechanism and the Thermal Stability of Fluorine Ions in GaN After Ion

Implantation. M.J.Wang, L.Yuan, K.J.Chen, F.J.Xu, B.Shen: Journal of Applied

Physics, 2009. 105[8], 083519