The mitigating effects of the threshold voltage shifting on the false turn-on of GaN E-HEMTs

Enhancement mode Gallium Nitride High-electron-mobility Transistors (GaN E-HEMTs) have displayed a great potential in boosting performances for power converters, compared with traditional Silicon power devices. However, in the bridge-leg configuration, GaN E-HEMTs are more subject to false turn-on due to its low threshold voltage and fast switching speed, resulting in undesired effects like higher switching loss and shooting through. In order to eliminate such effects, a -3.3 V gate voltage bias could be applied, whereas such a strong bias may lead to high reverse conduction loss. However, it is discovered that the threshold gate voltage of GaN E-HEMTs shifts with the voltage stress from drain to gate, and it will be higher than previous expectations. Thence, the dynamic behavior of the threshold voltage shifting and its benefit on the false turn-on is quantitatively analyzed. The false triggering would be suppressed even with a higher negative bias, due to the existence of the shift. Besides, the current overshoot during the false triggering process is especially suppressed according to the analysis.