Gate Leakage Suppression and Threshold Voltage Stability Improvement in GaN-Based Enhancement-Mode HEMTs on Ultrathin-Barrier AlGaN/GaN Heterostructures with a p-Doping-Free GaN Cap
摘要
GaN-based enhancement-mode high-electron-mobility transistors (HEMTs) with a 25-nm-thick undoped GaN (u-GaN) cap underneath the gate metallization on ultrathin-barrier (UTB) AlGaN (<6 nm)/GaN heterostructures have been demonstrated. The presence of a thick u-GaN cap contributes to the increased depletion of the two-dimensional electron gas (2DEG) beneath the gate by polarization effects, resulting in an improvement of the threshold voltage (Vth) and a suppression of the off-state gate leakage (Ioff). The UTB HEMTs with a thick u-GaN cap exhibit normally-off operation with a Vth of 0.5 V, a maximum on-current of 232.1 mA/mm, an Ioff of 10−6 mA/mm, and a gate voltage swing of 7 V at a drain bias of 10 V. Thanks to the p-doping-free GaN cap, the device demonstrates excellent Vth stability under positive gate bias, which positions it as a promising candidate for future low-voltage GaN power applications.