Identification of bulk and interface state-induced threshold voltage instability in metal/SiNx(insulator)/AlGaN/GaN high-electron-mobility transistors using deep-level transient spectroscopy

Abstract

The physical mechanism of threshold voltage (VTH) instability in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) was identified via capacitance-mode deep-level transient spectroscopy characterization. MIS-HEMTs with low-pressure chemical vapor deposited (LPCVD) SiNx as the gate insulator feature two distinctive trap-emission transients. The initial transient corresponds to emission of states at the SiNx/AlGaN interface, and the extracted density of state exhibits an exponential decay distribution. The subsequent transient is revealed due to hybrid emission of the interface and bulk states from the LPCVD-SiNx gate insulator, which features an activation energy higher than 1.1 eV and a capture cross section that ranges between 1 × 10−11 and 1 × 10−10 cm2. The bulk states in the LPCVD-SiNx gate insulator become charged under high gate voltage overdrive, leading to severe VTH instability in GaN-based MIS-HEMTs.