1.7-kV Vertical GaN p-n Diodes with Step-Graded Ion-Implanted Edge Termination.

GaN is promising for high-power applications as a result of its excellent properties including high critical electric field, high electron mobility and saturation velocity, and relatively high thermal conductivity. In practice, however, the reverse-bias performance of vertical GaN devices is limited by field crowding at the edge of the device. Junction termination extensions (JTEs) are widely used to reduce the field crowding in Si and SiC materials, but this approach is more difficult to realize in GaN because laterally-defined p-type doping in the nitrides is challenging. Nitrogen ion implantation has been shown to enable selective compensation of dopants incorporated during growth in the p-GaN epilayer to form JTE structures [1]–[2]. Mesa etching [3]–[4] and guard rings [5]–[6] have also been used in some works to form the edge termination (ET). However, in these designs the electric field still highly peaks at the edge of contact or ET [2]. In this work, we experimentally demonstrate a triple-zone step-graded JTE that effectively reduces the electric field peaks and improves the reverse performance of vertical GaN diodes.