Enhancement-mode GaN p-FET with p-NiO/p-GaN heterojunction gate featuring improved threshold voltage stability and channel conductivity based on low interface trap density

Abstract

Enhancement-mode (E-mode) p-channel field-effect transistors (p-FETs) remain challenging for GaN complementary logic (CL) technology due to their unstable threshold voltage (Vth), low current density, and large on-resistance (RON) at 6 V CL-compatible operation. In this work, we demonstrate a high-performance E-mode GaN p-FET with a p-NiO/p-GaN heterojunction gate. Notably, the suppressed Vth shift and improved channel conductivity were simultaneously achieved in the E-mode channel. The improvement is primarily due to the type-II band alignment at the p-NiO/p-GaN interface. This structure reduces band overlap, resulting in a low interface trap density (DT) of 3.29–5.71 × 1010 cm−2 eV−1 as measured by the sub-bandgap photo-assisted capacitance–voltage method. The fabricated device with LG/LGS/LGD = 1.5/3/3 μm exhibits a Vth of −0.6 V with a minimal hysteresis of 0.02 V and maximum shift of 0.04 V under stress, a ID of 5.5 mA/mm, a RON of 0.47 kΩ mm, and a transconductance (gm) of 1.8 mS/mm for 6 V CL-compatible operation.