Using Gate Leakage Conduction to Understand Positive Gate Bias Induced Threshold Voltage Shift in p-GaN Gate HEMTs

• Published in: IEEE transactions on electron devices 2023-02, Vol.70 (2), p.449-453
• Main Authors: Tang, Shun-Wei, Bakeroot, Benoit, Huang, Zhen-Hong, Chen, Szu-Chia, Lin, Wei-Syuan, Lo, Ting-Chun, Borga, Matteo, Wellekens, Dirk, Posthuma, Niels, Decoutere, Stefaan, Wu, Tian-Li
• Format: Article
• Language: English
• Subjects: Aluminum gallium nitride; Aluminum gallium nitrides; Bias; Current leakage; Gallium nitrides; GaN high electron mobility transistors (HEMTs); HEMTs; High electron mobility transistors; Junctions; Logic gates; MODFETs; p-GaN gate; PBTI; Semiconductor devices; Stress; Thermionic emission; Threshold voltage; VTH instability; Wide band gap semiconductors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2022.3231566

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 < {V}_{G} < 4 V), thermionic emission (TE) dominates in the AlGaN/GaN region, whereas in a higher bias range (4 V < {V}_{G} < 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 {E}_{A}\sim 0.6 eV is found. In conclusion, a physical model explaining the negative {V}_{\text {TH}} shift by considering TAT via hole transport is proposed.