It was demonstrated that the P diffusion doping of polycrystalline films that were deposited on SiO2 resulted in the movement of underlying Na, Li, K, and B impurities into the diffusion glass. It was suggested that the B and alkali element transport was due to the preferential segregation of impurities into the P glass via grain boundary diffusion. This behavior contrasted with that of Si films which had been doped  in situ  with P, and then recrystallized by annealing. In this case, no diffusion glass was formed and little or no impurity removal was detected. It was concluded that P-diffused polycrystalline material was a potentially better gate electrode for metal oxide semiconductor devices.

C.W.Pearce, J.L.Moore, F.A.Stevie: Journal of the Electrochemical Society, 1993, 140[5], 1409-13