Planar edge termination design and technology considerations for 1.7-kV 4H-SiC PiN diodes

This paper presents the design, fabrication, and comparison of different planar edge termination techniques on high-voltage 4H-SiC PiN diodes, including single- and double-junction termination extensions (JTE), floating guard rings, and a novel termination structure, the so-called "floating guard rings-assisted JTE." The influence of the anode metal edge location over different periphery regions on the breakdown voltage is also discussed, as well as the effect of a field plate and the passivation layer on the reverse characteristics. The terminations were studied by way of two-dimensional numerical device simulations and they are confirmed by fabricating and measuring 1.7-kV 4H-SiC aluminum implanted PiN diodes. It is shown that the novel termination structure provides the best results achieving the highest breakdown voltages with good production yield. The fabricated diodes also exhibited excellent forward current characteristics with a low on-state voltage drop of 3.0 V at 100 A/cm², thanks to the low specific contact resistivity achieved (ρ_C=1·10^-5 Ωcm²) after the high-temperature treatment of the anode contact. High-temperature reverse current-voltage measurements were also carried out and are presented and discussed.