P-GaN/AlGaN/GaN Fin-HEMT With High Saturation Current and Enhanced VTH Stability

AlGaN/GaN-based high electron mobility transistors with a p-type GaN cap (p-GaN HEMTs) has emerged as a promising normally-off device for high-voltage and high- power switching applications. However, p-GaN-HEMT still suffers from several critical issues, such as degradation of on-state resistance related to the difficulty of channel recovery under the p-GaN, and threshold voltage ( ${V}_{\text {TH}}\text {)}$ instability caused by poor gate controllability. In this work, a fin-gate p-GaN HEMT (p-GaN-Fin-HEMT) is proposed and fabricated, with narrower channel surrounded by tri-gates and fin-trenches extended to the gate-to-drain access region, to enhance the saturation current and improve the ${V}_{\text {TH}}$ stability. Compared with planar p-GaN HEMT, the p-GaN-Fin-HEMT exhibits 2.59 times of the saturation current at ${V}_{\text {GS}}-{V}_{\text {TH}}=2$ V and lower gate/drain coupled barrier lowering (GDCBL) of 2 mV/V. Besides, the high-temperature ${V}_{\text {TH}}$ stability of p-GaN-Fin-HEMT is superior to planar device, with ${V}_{\text {TH}}$ shift as low as 0.06 V at 80°C. Additionally, the ${V}_{\text {TH}}$ instability after bias stress is suppressed in p-GaN-Fin-HEMT, with ${V}_{\text {TH}}$ shift being reduced by 8 times compared with planar p-GaN HEMT. The underlying physical mechanism is that the fin structure effectively suppresses the emission of carriers by traps in the p-GaN layer. Besides, the trench extended to the gate-to-drain access region reduces the potential shift of p-GaN layer by reducing ${C}_{\text {GD}}$ . The p-GaN-Fin-HEMT structure proposed in this letter offers a novel solution for enhancing the ${V}_{\text {TH}}$ stability of p-GaN HEMTs.