It was noted that B diffused in crystalline Si by reacting with a Si self-interstitial (I) with a frequency, g, thus forming a fast-migrating BI-complex that could migrate over an average distance, λ. It was demonstrated experimentally that both g and λ depended strongly upon the free hole concentration, p. At low p, g had a constant trend and λ increased with p while, at high p, g exhibited a super-linear trend and  λ decreased with p. This demonstrated that BI formed in the 2 regimes by interaction with neutral and double positive I, respectively, and its charge state had to change by interaction with free holes before diffusing.

Atomistic Mechanism of Boron Diffusion in Silicon. D.De Salvador, E.Napolitani, S.Mirabella, G.Bisognin, G.Impellizzeri, A.Carnera, F.Priolo: Physical Review Letters, 2006, 97[25], 255902