The electrical activity of implanted Ga atoms was investigated during annealing, with or without a SiO2/SixNy/SiO2 capping film. A low electrical activity of the Ga atoms, in the absence of a capping film, was attributed to Ga out-diffusion. In order to prevent such out-diffusion, it was necessary to put a capping film on the Si surface during annealing. By using a capping film, an electrical activity of 75% could be obtained after annealing (1250C, 16h). It was suggested that Ga atoms which out-diffused from the Si substrate, and into the capping film, acted as a diffusion source, which then re-diffused Ga into the substrate.

M.Watanabe, O.Ishiwata, M.Nagano, H.Kirihata: Journal of the Electrochemical Society, 1992, 139[6], 1748-51