Vertical GaN Schottky barrier diodes with area-selectively deposited p-NiO guard ring termination structure

Abstract

In this study, the effect of p-NiO guard ring length on the properties of vertical GaN Schottky barrier diode was investigated extensively. The forward biased current-voltage characteristics of all diodes with different guard ring length follow the thermionic emission theory, showing nearly the same ideality factor and Schottky barrier height value. While the series resistance increases by nearly two times with the increasing guard ring lengths because the increasing depletion region at the p-NiO/n-GaN junction compresses the conduction path. Under reverse bias, the breakdown voltage of the SBD without any termination is relatively low due to the electric field crowding. The p-NiO guard ring is effective to enhance the breakdown voltage although the leakage current is comparable. However, the breakdown voltage decreases with the increasing guard ring length, which may be ascribed to the tunneling leakage caused by the imperfect p-NiO/n-GaN interface.