Novel Enhancement-Mode p-Channel GaN MOSFETs With an AlN Insert Layer

In this work, an enhancement-mode (E-mode) p-channel GaN metal-oxide-semiconductor field-effect transistor (p-MOSFET) with a maximum ON-state current ( ${I}_{\text {ON}}$ ) density of 10.5 mA/mm, threshold voltage ( ${V}_{\text {TH}}$ ) of −2.45 V, and ${I}_{\text {ON}}/{I}_{\text {OFF}}$ ratio of $10^{{8}}$ is demonstrated on a commercial GaN wafer designed on a p-GaN HEMT. Furthermore, we present a novel E-mode p-FET featuring an AlN insertion layer within the p-GaN layer. The AlN layer introduces extra capacitance in the conducting channel and decreases the body factor m of devices. The p-GaN/AlN/p-GaN/AlGaN structure reduces the equivalent channel capacitance, achieving a minimum point-by-point subthreshold swing (SS) of 60 mV/dec. Compared with that of the conventional p-GaN channel FET, the SS decreases from 225 to 105 mV/dec over three orders, the ${V}_{\text {TH}}$ shifts to −3.05 V, the ${I}_{\text {ON}}/{I}_{\text {OFF}}$ ratio increases to $2 \times 10^{{8}}$ , and the device also has an ultralow off-state leakage current in the range of $10 \; ^{-{8}}$ mA/mm. The proposed structure is compelling for GaN-based complementary metal-oxide-semiconductor (CMOS) logic and power devices.