The effect of Si3N4/Al2O3 stacked structure of AlGaN/GaN HEMTs

Abstract

Excessive gate leakage current and current collapse effects are the critical reliability issues for GaN-based high electron mobility transistors (HEMTs). In this paper, Si3N4 passivation layers was grown separately on p-GaN gate HRCL-HEMTs with or without Al2O3 film, and the gate leakage and current collapse effects of the devices and their intrinsic mechanisms were investigated. It is found that the device with Si3N4/Al2O3 stacked structure has better performance in terms of gate reverse leakage current, breakdown voltage, etc. The Al2O3 film blocking layer can reduce the H plasma damage to the channel, decrease the gate leakage, and the passivation can effectively suppress the increase of gate leakage current. Through variable temperature characteristic test, it is verified that the dominant mechanism of the device gate reverse leakage current is the two-dimensional variable range hopping (2D-VRH) model. The interface state between Si3N4 passivation layer and Al2O3 film increases the trap activation energy of the device, which is the reason for the reduction of gate reverse leakage current, and also causes the current collapse effect of the device.