Study on the Relationship Between Threshold Voltage Instability and Gate Leakage Current in p-GaN HEMTs

Abstract

This work uncovers a temperature-dependent relationship between gate leakage current ( $\mathrm{I}_{\mathrm{G}}$ ) and threshold voltage shift ( $\Delta \mathrm{V}_{\mathrm{TH}}$ ) through an evaluation combining deep level transient spectroscopy (DLTS) measurements, $\mathrm{I}_{\mathrm{G}}$ testing, and assessments of $\mathrm{V}_{\mathrm{TH}}$ instability. Analysis across a temperature range of 80 K to 440 K of p-GaN gate defects on device characteristics. These findings indicate that the same type of gate defects simultaneously affects both gate leakage and $\mathrm{V}_{\mathrm{TH}}$ instability. Specifically, defects release holes during positive gate stress. During low-bias $\mathrm{V}_{\text {TH }}$ measurement, the persistent negative charge from defects, due to slow hole re-trapping, enhances the depletion of the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface, reducing 2DEG density and causing a positive $\Delta \mathrm{V}_{\mathrm{TH}}$ . Furthermore, high-temperature gate bias (HTGB) stress significantly increases the concentration of relevant defects within the p-GaN gate, leading to a marked rise in both $\mathrm{I}_{\mathrm{G}}$ and $\Delta \mathrm{V}_{\mathrm{TH}}$ . Notably, the $\mathrm{I}_{\mathrm{G}} / \Delta \mathrm{V}_{\mathrm{TH}}$ ratio remains consistent even after HTGB stress. These observations provide valuable insights into the relationship between gate defects and the performance of p-GaN gate HEMT.