Ohmic contacts to silicon carbide determined by changes in the surface

In this study, we investigated the effects of the contact phases and the underlying SiC surface on the ohmic behavior of annealed Pt and Pt∕Si contacts to p-type 4H–SiC. The contacts were annealed at 1100 and 1000 °C, respectively, for 5 min in vacuum to form ohmic contacts. Our data show that although the formation of the PtSi phase was complete, and the only phase present in the Pt∕Si∕SiC samples annealed at 900 °C, the contacts did not become ohmic at this temperature. Removal of the annealed Pt and Pt∕Si contacts and their replacement with unannealed Ni contacts resulted in ohmic behavior that was nearly identical to that of the previous annealed contacts. In contrast, as-deposited Ni contacts on as-received p-type SiC resulted in rectifying contacts. The results of this study show that changes in the SiC substrate underneath the contacts dominate the electrical behavior, and that effects of the particular phase(s) formed are small.