The B diffusion from gas phase was implemented for p-type doping of 4H-SiC at 1800 to 2000C. A 2-branch diffusion associated with 2 different diffusion mechanisms was observed. The results could be described by:

D (cm2/s) = 1.931 x 106exp[-7.258(eV)/kT]

and

D (cm2/s) = 2.126 x 107exp[-8.742(eV)/kT]

for fast and slow diffusion, respectively. It was confirmed that the surface layer of diffused B mostly consists of shallow boron acceptors, while the tail of diffusion profile has mostly deep level D centres.

Investigation of Two-Branch Boron Diffusion from Vapor Phase In N-Type 4H-SiC. A.V.Bolotnikov, P.G.Muzykov, T.S.Sudarshan: Applied Physics Letters, 2008, 93[5], 052101