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

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 similar to 0.6 eV is found. In conclusion, a physical model explaining the negative V-TH shift by considering TAT via hole transport is proposed.

Automated summary

The gate current characteristics in AlGaN/GaN high electron mobility transistors (HEMTs) with a p-GaN gate were investigated to explain the threshold voltage shift. The intrinsic gate current conduction mechanisms were identified as thermionic emission (TE) in the AlGaN/GaN region at low bias range (2.5 V < V-G < 4 V) and trap-assisted tunneling (TAT) in the Schottky/p-GaN region at higher bias range (4 V < V-G < 7 V). The threshold voltage shift in the stress phase was found to be consistent with a trap level having an activation energy of E-A similar to 0.6 eV. A physical model considering TAT via hole transport was proposed to explain the negative V-TH shift.