The reduction of reverse leakage currents was attempted to fabricate 4H-SiC diodes with large current capacity for high voltage applications. Firstly diodes with Schottky metal of titanium (Ti) with active areas of 2.6 mm2 were fabricated to investigate the mechanisms of reverse leakage currents. The reverse current of a Ti Schottky barrier diode (SBD) is well explained by the tunneling current through the Schottky barrier. Then, the effects of Schottky barrier height and electric field on the reverse currents were investigated. The high Schottky barrier metal of nickel (Ni) effectively reduced the reverse leakage current to 2 x 10-3 times that of the Ti SBD. The suppression of the electric field at the Schottky junction by applying a junction barrier Schottky (JBS) structure reduced the reverse leakage current to 10-2 times that of the Ni SBD. JBS structure with high Schottky barrier metal of Ni was applied to fabricate large chip-size SiC diodes and we achieved 30 A- and 75 A-diodes with low leakage current and high breakdown voltage of 4 kV.
SiC trench MOSFET with integrated side-wall Schottky barrier diode having P+ electric field shield
