Effects of sacrificial oxidation on surface properties of n- and p-type 4H-SiC: implications for metal contact behaviors

A comparative investigation on the effects of sacrificial oxidation (SO) on the surface properties of n- and p-type 4H-SiC has been conducted by using x-ray photoelectron spectroscopy and deep level transient spectroscopy. For n-type 4H-SiC, the surface Fermi level is unpinned and shifts towards conduction band edge due to significant reduction of surface contaminants and removal of surface defects by SO. For p-type 4H-SiC, the surface contamination is also reduced with a shift of Fermi level towards valance band edge after SO. However, a high density of carbon interstitials related defects is likely to be generated close to the valance band during the oxidation. Pronounced Fermi level pinning may be still present with surface states density higher than 1.65 x 10(12) cm(-2) eV(-1). The implications of SO on the electrical behaviors of metal contacts to n- and p-type 4H-SiC have been proposed.