Ohmic contact properties of Ni/C film on 4H-SiC

Ohmic contact formation of Ni/C film on n-type 4H-SiC is investigated. A carbon interfacial layer between Ni film and SiC is used to improve ohmic contact properties. The contact properties of Ni/C/SiC structure with various thickness of carbon film, annealing time, and annealing temperatures are examined. The low specific contact resistivities at 10−6–10−7 Ω cm2 are achieved on the SiC with a doping concentration of 3.1 × 1019 cm−3 after annealing at 700–800 °C in Ar for 2 h. For the Ni/C/SiC with moderate doping concentrations of 1.6 × 1018 and 1.1 × 1017 cm−3, the specific contact resistivities at 10−5 Ω cm2 are formed after annealing at 900–1000 °C. Raman spectroscopy, scanning electron microscopy, and atomic force microscopy are used for characterizations of carbon structural evolutions and film morphology, and are interpreted by the catalytic graphitization mechanism. The formation of nano-size graphitic structures and related structures results in the formation of ohmic contact on SiC, and Ni as a graphitization catalyst accelerates the graphitization process.