The dopant was diffused, into (111) single crystals having dislocation densities of less than 500/cm2, under intrinsic vacuum sealed tube conditions. It was found that the low-concentration migration of the dopant from the vapor phase into the bulk was markedly affected by a surface rate limiting process. The diffusion data for between 1100 and 1250C could be described by:

D(cm2/s) = 2.46 x 100exp[-3.59(eV)/kT]

Low Concentration Diffusion in Silicon under Sealed Tube Conditions. R.N.Ghoshtagore: Solid State Electronics, 1972, 15[10], 1113-20