Abstract: An investigation of Au/Ti/Ni and Au/Ti/Pt ohmic contacts to n-type 4H-SiC and the behavior of metal films on SiC with thermal anneals is reported.Specific contact resistance as low as 2.765e-6Ω· cm2 was achieved after rapid thermal annealing in N2 for 2min at 950℃.SIMS analysis shows that the formation of Ni silicide after annealing supported a number of carbon atoms’ outdiffusion from the SiC to form interstitial compound TiC.This process can create abundant C vacancies near the interface.It is the carbon defect layer that enhances the defect-assisted tunneling.The interface band structure within the defect level could make it clear why the metal-SiC contacts become ohmic during annealing.

Key words: silicon carbide, ohmic contact, carbon vacancy, interface band structure