摘要
We optimize epitaxy and device architecture to improve the DC and RF performance of GaN-on-Si HEMTs simultaneously. The study explores quaternary InAlGaN/GaN barriers with calibrated Al compositions and a 1.5-nm AlN spacer to strengthen polarization coupling and 2DEG confinement and implements an air-surrounding T-gated (AS-TG) module that forms a 50 nm air gap to effectively reduce the equivalent dielectric constant of the passivation stack, thereby minimizing parasitic capacitances (C gs and C gd ). Epitaxial tuning increases drive current, reduces on-resistance, and boosts g m -while revealing the expected trade-off of more negative V th and enlarged subthreshold swing under excessive polarization. Integrating AS-TG with a 0.15 μm T-gate raises f T about 33% in the binary barrier. These results validate materials-to-device co-design as a practical path to high-efficiency, high-frequency GaN RF power amplification.