Edge-Termination Technique for High-Voltage Mesa-Structure 4H-SiC Devices: Negative Beveling

The prospects for the protection of high-voltage 4H-SiC-devices from edge breakdown via the formation of mesa structures with inclined walls (negative beveling) are considered. Numerical simulation of the spatial electric-field distribution in high-voltage (similar to 1500V) reverse-biased mesa-epitaxial p(+)-p-n(0)-n(+) 4H-SiC diodes is performed. It is shown that negative beveling with small angles of less than 10 degrees from the plane of the p-n(0) junction makes it possible to reduce severalfold the surface edge electric field as compared to that in the bulk. A combined protection method is suggested as the edge-termination technique for 4H-SiC diodes with a p(+)-n(0)-n(+) structure, Schottky diodes with an n(0) blocking base, and bipolar n(+)-p-n(0) transistors via the implantation of boron along with negative beveling. The possibility of fabricating mesa structures with inclined walls via the photolithography and dry etching of silicon carbide is briefly discussed.