High voltage vertical p-n diodes with ion-implanted edge termination and sputtered SiNx passivation on GaN substrates

Abstract

High-voltage vertical GaN-on-GaN power diodes with partially compensated ion-implanted edge termination (ET) and sputtered SiNx passivation are reported. The measured devices exhibit a breakdown voltage (Vbr) exceeding 1.2 kV. Optimization of the ion-implantation-based ET has been performed through simulation and experiment, and the impact of SiNx surface passivation on breakdown has also been evaluated. Use of a partially-compensated ET layer, with approximately 40 nm of the p-type anode layer remaining uncompensated by the implant, is optimal for maximizing Vbr. Additionally, sputter-deposited SiNx, rather than the more conventional plasma-enhanced chemical vapor deposition (PECVD)-based SiNx, results in less degradation in the on-state performance while providing the same Vbr. The diodes support current densities of 8 kA/cm2 at a forward voltage 5 V, with differential specific on resistances (Ron) of 0.11 mΩcm2. A Baliga's figure-of merit (BFOM) of 13.5 GW/cm2 is obtained; this is among the highest reported BFOM for GaN homoepitaxial pn diodes.