High-Performance Enhancement-Mode p-Channel GaN MISFETs With Steep Subthreshold Swing

We report an enhancement-mode (E-mode) <tex-math notation="LaTeX">p </tex-math> -channel GaN heterojunction field-effect transistor with a metal-insulator-semiconductor gate structure. A 60 mV/dec subthreshold swing is experimentally achieved in the E-mode GaN <tex-math notation="LaTeX">p </tex-math> -channel transistors on an unintentionally doped GaN interlayer for the first time by using a low-power plasma gate recessing etch and gate dielectric deposition pre-treatment. The fabricated <tex-math notation="LaTeX">p </tex-math> -channel transistors exhibit excellent E-mode performance with a threshold voltage of −1.53 V, an effective on-resistance of 1.0 <tex-math notation="LaTeX">kΩ </tex-math> .mm, a peak transconductance of 1.0 mS/mm, and a high <tex-math notation="LaTeX">ION/IOFF </tex-math> ratio > 10 7 . Bi-directional gate sweep measurements on the p-channel devices show a threshold voltage shift of 0.12 V and an increased subthreshold swing of 107 mV/dec. In addition, the dual-channel conduction mechanism in the <tex-math notation="LaTeX">p </tex-math> -channel GaN transistors is presented and discussed.