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

We report an enhancement-mode (E-mode)
${p}$
-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
${p}$
-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
${p}$
-channel transistors exhibit excellent E-mode performance with a threshold voltage of −1.53 V, an effective on-resistance of 1.0
$\text{k}\Omega $
.mm, a peak transconductance of 1.0 mS/mm, and a high
$\text{I}_{ \mathrm{\scriptscriptstyle ON}}/\text{I}_{ \mathrm{\scriptscriptstyle OFF}}$
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
${p}$
-channel GaN transistors is presented and discussed.