p-GaN Gate HEMTs With Tungsten Gate Metal for High Threshold Voltage and Low Gate Current

The impact of gate metals on the threshold voltage <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">(VTH)</tex> </formula> and the gate current of p-GaN gate high-electron-mobility transistors (HEMTs) is investigated by fabricating p-GaN gate HEMTs with different work function gate metals—Ni and W. p-GaN gate HEMTs incorporate a p-GaN layer under the gate electrode as the gate stack on top of the AlGaN/GaN layer. In comparison to the Ni-gate p-GaN HEMTs, the W-gate p-GaN HEMTs showed a higher <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">VTH</tex></formula> of 3.0 V and a lower gate current of 0.02 mA/mm at a gate bias of 10 V. Based on TCAD device simulations, we revealed that these high <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">VTH</tex></formula> and low gate current are attributed to the low gate metal work function and the high Schottky barrier between the p-GaN and the W gate metal.