Performance Enhancement of T-gated GaN HEMTs Using Polarization-Graded AlGaN Back Barrier for High-Frequency Applications

This paper proposes a polarization-graded AlGaN back barrier to improve the direct current and RF performance of GaN-based High Electron Mobility Transistors (HEMTs). The device structure integrates a Silicon Carbide (SiC) substrate, a T-gate configuration, and a graded AlGaN back barrier. Sentaurus TCAD simulations are employed to analyze both graded and non-graded structures. For LG = 0.3 µm, the maximum drain current (IDmax) increases from 1.14 A/mm in the Non-graded case to 1.44 A/mm in the Graded structure. Similarly, transconductance (gm) improves from 175.46 to 191.04 mS/mm, cutoff frequency (FT) increases from 219.26 to 272.92 GHz, and maximum oscillation frequency (Fmax) rises from 221.31 to 279.8 GHz. These improvements demonstrate that combining a SiC substrate, a T-gate, and a graded AlGaN back barrier enhances device performance, offering strong potential for next-generation high-frequency and high-power applications.