Using Gate Leakage Conduction to Understand Positive Gate Bias Induced Threshold Voltage Shift in p-GaN Gate HEMTs
Shun‐Wei Tang, Benoit Bakeroot, Zhen-Hong Huang, Szu-Chia Chen, Wei-Syuan Lin, Ting-Chun Lo, Matteo Borga, D. Wellekens, Niels Posthuma, Stefaan Decoutere, Tian‐Li Wu
Abstract
In this work, the gate current characteristics are investigated to explain the threshold voltage shift in AlGaN/GaN high electron mobility transistors (HEMTs) with a p-GaN gate. First, the intrinsic gate current conduction mechanisms are identified: in the low bias range (2.5 V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ < {V}_{G} < $ </tex-math></inline-formula> 4 V), thermionic emission (TE) dominates in the AlGaN/GaN region, whereas in a higher bias range (4 V <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ < {V}_{G} < $ </tex-math></inline-formula> 7 V) trap-assisted tunneling (TAT) is occurring in the Schottky/p-GaN region. Secondly, the threshold voltage shift of the stress phase is evaluated by applying a positive gate bias for various stress times. A consistent trap level with an activation energy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{A}\sim $ </tex-math></inline-formula> 0.6 eV is found. In conclusion, a physical model explaining the negative <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {TH}}$ </tex-math></inline-formula> shift by considering TAT via hole transport is proposed.