The role of SiNx passivation using two different deposition techniques, namely Inductively Coupled Plasma Chemical Vapor Deposition (ICPCVD) and Plasma Enhanced Chemical Vapor Deposition (PECVD) on gate reverse leakage current of AlGaN/GaN HEMTs was studied. It was observed that devices having PECVD SiNx films exhibit higher leakage than devices with ICPCVD SiNx films. To understand the mechanism behind this behavior, the role of Poole-Frenkel emission on gate reverse leakage current for both the types of passivation schemes was investigated.