HEMTs With Side-Source-Via for Optimizing the Performance and Size of High-Power Amplifiers

Back-via positioning of a gallium nitride (GaN)-on-silicon carbide (SiC) HEMT is studied to optimize RF performance and area utilization. Placing a back-via for every individual source achieves the best RF performance but results in a large area and an inconvenient aspect ratio. If only two back-vias are used at the outer sources, the increased source inductance reduces the performance. Positioning the source-vias at the gate side of HEMT side-source-via (SSV) results in a smaller source inductance and a more favorable aspect ratio. A three-stage monolithic microwave integrated circuit (MMIC) is designed using SSV HEMTs with a 0.25- $\mu $ m GaN-on-SiC process. The design achieves over 45 W of output power with a typical power-added efficiency of 40% across the operational frequency range of 8–12.5 GHz.