Investigation of Ta/Ni bilayered ohmic contacts on n-type SiC single-crystal substrate

The interfacial reactions between a Ta/Ni bilayered film and SiC single-crystal substrate during annealing at 650–1,100 °C were investigated. It was found that H-Ni2Si (hexagonal Ni2Si) and TaC formed at the interface as a result of thermal annealing. A small amount of free C atoms diffused outwards the surface, leading to the formation of carbon vacancies that could act as electron donors. The electrical properties of the contacts showed that ohmic behavior was observed for the sample annealed above 800 °C. The specific contact resistivity was determined to be as low as 4.4 × 10−4 Ω cm2 at 1,100 °C.