Fabrication and characterization of high voltage Ni/6H-SiC and Ni/4H-SiC Schottky barrier diodes

Ni/SiC Schottky diodes have been fabricated using 4H-SiC and 6H-SiC epitaxial wafers. The n-type epitaxial layers grown on n⁺ substrates have a doping concentration of 4.0×10¹⁶ cm^-3 and a thickness of 10 μm. Oxide edge termination has been adopted in order to obtain high breakdown voltage and low leakage current. The fabricated Ni/4H-SiC and Ni/6H-SiC Schottky barrier diodes show excellent rectifying characteristics up to the maximum measured temperature of 550 °C. In case of oxide terminated Schottky barrier diodes, breakdown voltages of 973 V (Ni/4H-SiC diode) and 920 V (Ni/6H-SiC diode), and a very low leakage current of less than 1 nA at -800 V have been observed at room temperature. On Schottky barrier diodes without edge termination, breakdown voltages were 430 V (Ni/4H-SiC) and 160 V (Ni/6H-SiC), respectively. At room temperature, Schottky barrier height (SBH), ideality factor, and specific on-resistance were 1.55 eV, 1.3, 3.6×10^-2 Ω · cm² for Ni/4H-SiC Schottky barrier diodes, and 1.24 eV, 1.2, 2.6×10^-2 H - cm₂ for Ni/6H-SiC Schottky barrier diodes, respectively. These results show that both Ni/4H-SiC and Ni/6H-SiC Schottky barrier diodes are very promising for high temperature and high voltage applications.