Silicon carbide pinch rectifiers using a dual-metal Ti-Ni2Si Schottky barrier

The electrical characterization of dual-metal-planar Schottky diodes on silicon carbide is reported. The devices were fabricated on both 6H- and 4H-SiC by using titanium (Ti) and nickel silicide (Ni₂Si) as Schottky metals. These rectifiers yielded the same forward voltage drop as the Ti diodes and leakage current densities comparable to those of the Ni₂Si diodes. The reduction of the reverse leakage current density, with respect to that of the Ti diodes, was about three orders of magnitude in 6H and about a factor of 30 in 4H-SiC. All that results in a consistent reduction of the device power dissipation. Electrical characterization of the devices at different temperatures provided insight into the carrier transport mechanism. In particular, the electrical behavior of the system was explained by an "inhomogeneous" Schottky barrier model, in which the low Ti barrier determines the current flow under forward bias, whereas the high Ni₂Si barrier dominates the reverse bias conduction by the pinchoff of the low barrier Ti regions.