Experimental and numerical analysis of VTH and RON drifts in E-mode GaN HEMTs during switch-mode operation

The evaluation and investigation of electrical parameters drifts during device operation is one of the mandatory task that has to be performed in order to improve GaN-power devices stability. In this work the authors would like to present novel results concerning the analysis of V TH and R ON drifts in E-mode GaN HEMT observed during their switch-mode operation. Two different mechanisms are observed for the induced positive V TH shift. The first one is related to electron injection from the 2DEG into dielectric/semiconductor traps beneath the gate region of the device, while a second one linked to electron injection from the gate terminal induces a V TH shift linked to a localized negative trapping mechanism in the drain-edge of the gate terminal. The observed R ON increase is instead linked to a hole-emission process taking place in the gate-drain access region within the device carbon-doped buffer layers. The negative charge build-up related to the ionized acceptor traps leads to the 2DEG depletion and consequent R ON increase.