Simulation of Gate Leakage Current of AlGaN/GaN HEMTs: Effects of the Gate Edges and Self-Heating

Abstract

The gate leakage current (IG) of AlGaN/GaN high electron mobility transistors (HEMTs) at various ambient temperatures is simulated by considering its mechanism as domination of trap-assisted tunneling (TAT) and Poole-Frenkel (PF) emission for low electric field in the AlGaN barrier, and domination of Fowler–Nordheim (FN) tunneling for high electric field in the AlGaN barrier. Two bias cases are studied: VGS (gate voltage) variation while VDS (drain voltage) = 0 V without self-heating and VDS variation while VGS = 0 V with self-heating. For the first case, FN tunneling current mainly concentrates near the gate edges and so it is not changed with the gate length. While PF emission and TAT current do not show big variation along the gate, they are affected by the gate length and show higher values for longer gate. For the second case, with VDS increasing the elevated device temperature caused by the self-heating obviously increases PF emission and also increases IG because PF emission is the dominant mechanism of IG. With VDS further increasing, although the higher device temperature presents, IG is not affected by the self-heating because the temperature-independent FN tunneling becomes the dominant mechanism of IG.