The thermal stability of Ni and Ni/Au ohmic contacts to n-type 4H-SiC

The thermal stability of ohmic contacts to 4H-SiC was studied by ageing test for the high power and high temperature application of SiC devices. Ni and Ni/Au ohmic contacts in a transmission line model (TLM) test structure were formed on n-type 4H-SiC with rapid thermal annealing (RTA). The as-annealed contact resistivity was in the range of 10³∼10^-6 Ωcm². The contact resistivity after ageing at 500°C showed that Ni ohmic contacts were thermally stable and Ni/Au ohmic contacts were not. The chemical component depth profiles of Auger electron spectroscopy (AES) measurement also showed Ni ohmic contacts thermally stable, and suggest the formation of passivation layer on the surface of Ni/Au contacts after RTA process.