Improved RF Performances by Applying Asymmetric Passivation and Air-Bridged Field Plate in AlGaN/GaN HEMTs With Reliability-Based Simulation

This study proposes an approach to enhance frequency characteristics for AlGaN/gallium nitride (GaN) high-electron-mobility transistors (HEMTs) by employing an air-bridged source-connected field plate to an asymmetric passivation structure. To overcome simulation limitations, we performed the device simulation by matching simulated results with measured data, applying various simulation models, and performing comparative analysis of frequency characteristics between simulated and calculated values using a small-signal equivalent circuit. Thus, the simulation results were well matched with the measured data, achieving an error rate of 1.4%, confirming the device simulation reliability. Asymmetric passivation HEMT for conventional source-connected field plate structures exhibited reduced parasitic capacitances, with notable increased cutoff and maximum oscillation frequencies by 21.7% and 7.8%, respectively. We applied an additional air-bridged source-connected field plate structure to the asymmetric passivation HEMT to further enhance RF performance, significantly increasing cutoff frequency by 31.6% compared with asymmetric passivation with source-connected field plate structure. These results represent outstanding RF performance without any degradation of dc characteristics.