Investigation of two-branch boron diffusion from vapor phase in n-type 4H-SiC

Boron diffusion from gas phase was implemented for p-type doping of 4H-SiC at temperatures in the range of 1800–2000°C. A two-branch diffusion associated with two different diffusion mechanisms was observed. The activation energy Ea and prefactor D0 were calculated for each diffusion branch, that are Ea=7.258eV∕D0=1.931×106cm2∕s and Ea=8.742eV∕D0=2.126×107cm2∕s for fast and slow diffusion, respectively. It has been confirmed that the surface layer of diffused boron mostly consists of shallow boron acceptors, while the tail of diffusion profile has mostly deep level D centers.