Ohmic contact formation mechanism of Ni on n-type 4H–SiC

Ohmic contact formation mechanism of Ni on n-type 4H–SiC is proposed by comparing the electrical properties with microstructural change. The ohmic behavior was observed at temperatures higher than 900 °C, but Ni2Si phase, as formerly reported to be responsible for ohmic contact, was formed after annealing at 600 °C. The higher work function of Ni2Si than Ni and the observation of graphite phase on the surface of Ni silicide after annealing at 950 °C support that a number of carbon vacancies were produced below the contact, playing a key role in forming an ohmic contact through the reduction of effective Schottky barrier height for the transport of electrons.