Toward a better understanding of Ni-based ohmic contacts on SiC

Abstract

There is still little consensus regarding why low contact resistivity is achieved when Ni on n-type 4H- and 6H-SiC is annealed at temperatures above 950°C. The objective of this paper is to provide an answer to this question. It has been reported that even Ni-based contacts formed in the n++ region exhibited a steep reduction of contact resistivity in an annealing temperature range > 900°C. This reduction cannot be explained by the carbon vacancy induced donor model (Vc model) proposed by Han and his coworkers [Appl. Phys. Lett., Vol. 79, p. 1816 (2001)]. It was observed that the surface of substrates annealed at 1000°C was not covered with Ni2Si but with a thin layer of NiSi. Finally, a plausible model is proposed that annealing at higher temperatures results in the formation of a NiSi/SiC system at the substrate interface, causing contact resistivity to be reduced significantly. © (2011) Trans Tech Publications.