The intrinsic diffusion of P and B in high-purity epitaxial Si films was studied (figures 4 and 5). The P diffusion at 810 to 1100C could be described by:

D (cm2/s) = 8 x 10-4 exp[-2.74(eV)/kT]

At 810 to 1050C, the B diffusion could be described by:

D (cm2/s) = 6 x 10-2 exp[-3.12(eV)/kT]

These results differed from those of many previous studies, but this deviation may to a large extent be attributed to slow transients before equilibrium concentrations of point defects were established below about 1000C. Despite a similar diffusion mechanism mediated by Si self-interstitials, P exhibited a lower activation energy than B because of stronger bonding to the Si self-interstitial.

Phosphorus and Boron Diffusion in Silicon under Equilibrium Conditions. J.S.Christensen, H.H.Radamson, A.Y.Kuznetsov, B.G.Svensson: Applied Physics Letters, 2003, 82[14], 2254-6

Figure 5

Diffusivity of P in Si