Polarization‐Engineered GaN‐Based High‐Electron‐Mobility Transistors for High Power RF Applications

Gallium nitride (GaN)‐based high‐electron‐mobility transistors (HEMTs) are advantageous for power RF applications due to their dense 2DEG and high mobility. However, at mm‐wave frequencies, the lateral scaling required to achieve high‐frequency operation reduces breakdown voltage, limiting output power. Polarization grading of the barrier offers a solution by enhancing both RF performance and breakdown voltage. This study evaluates nonlinear grading profiles, which improve power handling without the need for additional field plates. Simulations using Synopsys Sentaurus technology computer‐aided design (TCAD) reveal that polarization‐graded HEMTs, featuring a graded AlGaN barrier layer (6–18 nm), exhibit more negative threshold voltage, increased drain current, and flatter transconductance compared to conventional abrupt‐interface HEMTs. The graded layer reduces peak lateral electric fields by as much as 39%, resulting in breakdown voltages that are 2.2 times higher than reference HEMT structures without grading. Polarization‐graded HEMTs with an 18 nm graded layer achieve a maximum output power of 8.8 W mm −1 , nearly three times that of conventional HEMTs. These results demonstrate the potential of polarization‐graded structures for mm‐wave applications, enhancing intrinsic field and power‐handling capabilities.