Electrical characteristics of Schottky contacts on Ge-doped 4H-SiC

We report on the electrical characteristics of Ni/4H-SiC Schottky contacts fabricated on a Ge-doped 4H-SiC epilayer. The morphology and the current mapping carried out by conductive atomic force microscopy on the epilayer allowed observing nanoscale preferential conductive paths on the sample surface. The electrical characteristics of Ni contacts have been studied before and after a rapid thermal annealing process. A highly inhomogeneous Schottky barrier was observed in as-deposited diodes, probably related to the surface electrical inhomogeneities of the 4H-SiC epilayer. A significant improvement of the Schottky diodes characteristics was achieved after annealing at 700 degrees C, leading to the consumption of the near surface epilayer region by Ni/4H-SiC reaction. After this treatment, the temperature behavior of the ideality factor and Schottky barrier height was comparable to that observed on commercial 4H-SiC material.