Device-level co-integration of direct liquid cooling in GaN-on-SiC RF HEMTs

초록

Gallium nitride on silicon carbide high electron mobility transistors are key enabling devices for high power radio frequency systems. Their performance and reliability are increasingly constrained by self-heating under high power density operation. While silicon carbide substrates provide favorable thermal conductivity, continued scaling toward higher output power intensifies junction heating and exacerbates electro thermal coupling effects that degrade radio frequency performance. In parallel, stable operation at millimeter wave frequencies requires a grounding architecture with minimal parasitic inductance. Despite their interdependence, thermal management and grounding design have largely been addressed as separate challenges. Here we demonstrate a device level GaN on SiC HEMT architecture that co-integrates direct liquid cooling and low inductance grounding within a single die. An embedded microchannel is formed beneath the source region by selective etching of the GaN and SiC layers, enabling coolant flow in close proximity to the active region. In parallel, a through substrate via (TSV) establishes a shortened electrical return path through backside metallization. This co-designed electro thermal structure eliminates additional thermal interfaces while simultaneously reducing junction thermal resistance and grounding parasitics. The integrated cooling channel enables a maximum removable heat flux of 14.41 kW°cm−2 representing a 74.4 % increase compared with a reference conduction cooled package. The junction to coolant thermal resistance is reduced to 0.0061 cm2·K·W−1, confirming the effectiveness of device level direct cooling. These thermal improvements translate directly into enhanced electrical performance, including suppressed self-heating induced resistance increase and higher drain current under identical bias conditions. This work establishes device level electro thermal co-integration as an effective design paradigm for high power density GaN radio frequency electronics, providing a scalable pathway toward simultaneous thermal reliability and electrical performance enhancement in next generation millimeter wave systems.

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