Schottky ohmic transition in nickel silicide/SiC-4H system: is it really a solved problem?

The transition from Schottky to ohmic contact in the nickel silicide /SiC system during annealing from 600 to 950 °C was investigated by measuring the electrical properties of the contact and by analyzing the microstructure of the silicide /SiC interface. The graphite clusters formed by carbon atoms during silicidation are uniformly distributed into the silicide layer after annealing at 600 °C and they agglomerate into a thin layer far from the silicide /SiC interface after annealing at 950 °C. At this temperature an increase of the Schottky barrier height was measured, while deep level transient spectroscopy evidences the absence of the 0.5 eV peak related to the carbon vacancies.