Role of carbon in the formation of ohmic contact in Ni/4H SiC and Ni/Ti/4H SiC

Abstract In this work, we focus on the role of carbon in the Ni and Ni/Ti contacts on n-type 4H SiC. The contacts, formed on the backside of the wafers C-face by electron gun evaporation and annealed at 950 °C, were studied by Raman spectroscopy (RS), X-ray diffraction (XRD) and Auger electron spectroscopy (AES). The results show that titanium acts as a diffusion barrier for Si and C preventing the formation of the unfavourable phase NiSi and interacts with carbon to form TiC. The transformation of carbon to graphitic structure (in Ni/Ti/SiC) considerably lowers the sheet resistance and greatly improves the ohmic contact.