Investigation on Stability of p-GaN HEMTs With an Indium–Tin–Oxide Gate Under Forward Gate Bias

Abstract

In this study, p-GaN HEMTs with an indium-tin-oxide (ITO) electrode fabricated on the two different Mg concentration, i.e., $1 \mathbf {\mathrm {\times }} 10 ^{19}$ cm −3 and $8 \mathbf {\mathrm {\times }} 10 ^{19\,\,}$ 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 ${\mathrm {V}}_{TH}$ 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 ${\mathrm {V}}_{TH}$ 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 ${\mathrm {V}}_{TH}$ shift under a forward gate bias is observed, indicating a trade-off between the gate breakdown voltage and ${\mathrm {V}}_{TH}$ instability needs to be carefully considered to optimize the forward gate bias stability in p-GaN HEMTs with an ITO electrode.

Keywords

• GaN
• high electron mobility transistor (HEMT)
• indium–tin–oxide gate electrode
• PBTI