Edge-termination technique for high-voltage mesa-structure 4$H$-SiC devices: negative beveling

The prospects for the protection of high-voltage 4$H$-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 ($\sim$1500V) reverse-biased mesa-epitaxial $p^{+}$–$p$–$n_{0}$–$n^{+}$ 4$H$-SiC diodes is performed. It is shown that negative beveling with small angles of less than 10$^\circ$ 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 4$H$-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.