Thermal Management with AlN Passivation in AlGaN/GaN HEMTs with an Air Gap Gate for Improved RF Performance: A Simulation Study

This study introduces an air gap gate with AlN passivation to enhance the radio frequency (RF) performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) while addressing thermal challenges. The air gap gate improves RF performance by reducing gate capacitance, resulting in a 23.9% increase in cutoff frequency (35.82 GHz) and enhancing saturation drain current and maximum transconductance by 3.7% and 10.27%, respectively, compared to a 0.15 μm planar gate baseline. However, reduced heat dissipation degrades thermal performance, as reflected in higher thermal resistance and temperature gradients. Incorporating high thermal conductivity AlN passivation mitigates these drawbacks, lowering operating temperatures and improving heat distribution, while maintaining a 17.5% cutoff frequency improvement over the baseline. These results demonstrate that the air gap gate with AlN passivation provides an effective strategy for achieving reliable, high-performance AlGaN/GaN HEMTs under high-frequency and high-power operations.