Investigation on Stability of p-GaN HEMTs with an Indium-Tin-Oxide Gate under Forward Gate Bias

In this study, p-GaN HEMTs with an indium-tin-oxide (ITO) electrode fabricated on the two different Mg concentration, i.e., 1 × 1019 cm -3 and 8 × 1019 cm -3,in p-GaN layer are investigated for the first time under the forward gate bias to understand the stability of the forward gate bias breakdown and VTH shift stability. First of all, a Mg concentration in p-GaN layer results in a better Ohmic characteristic between the ITO and p-GaN contact. Furthermore, the fabricated device with a high Mg concentration of p-GaN layer shows a better forward gate breakdown voltage, which can be attributed to the better Ohmic characteristic between p-GaN and ITO electrode. Last, an obvious negative VTH shift is observed, which is most probably related to the hole injections/trapping effects. In sum, the gate breakdown characteristic in p-GaN HEMTs with ITO electrode can be further improved while using high Mg concentration of p-GaN layer while an obvious a negative VTH shift under a forward gate bias is observed, indicating a trade-off between the gate breakdown voltage and VTH instability needs to be carefully considered to optimize the forward gate bias stability in p-GaN HEMTs with an ITO electrode.