Reduction of leakage current at the SiNx/GaN interface in GaN Schottky diodes

Abstract

The breakdown characteristics for a GaN wrapround field plate diode are compared to those of a planar diode and a mesa diode to determine the improvement due to the field plate geometry. Mesa diodes exhibit a higher breakdown voltage compared to planar diodes, in agreement with simulation models. Wraparound field plate diodes, however, show high leakage current resulting in lower breakdown values than predicted. It is found that the extra leakage is caused by damage from the plasma enhanced chemical vapor deposition of the SiNx used to form the field plate. To mitigate the leakage current, atomic layer deposition was used to put down a protective Al2O3 prior to SiNx deposition. This significantly reduced the leakage current and raised the breakdown voltage of the wraparound Schottky diodes.