High power density gallium nitride radio frequency transistors via enhanced nucleation in heteroepitaxy.

Gallium-nitride high-electron-mobility-transistor is an industrial leading contender for high-frequency and high-power radio-frequency applications. However, the record output-power-density has remained stagnant for nearly two decades, limited by high thermal-resistances at the nucleation layer-substrate interface and thick nitride layers. Here, we propose induced nucleation by implementing ion-implantation on silicon-carbide substrate to create nano- to microscale surface nucleation-sites. This approach suppresses conventional island-like nucleation, enabling rapid film coalescence and aggressive reduction in buffer layer thickness while maintaining low dislocation density. Therefore, a low thermal-resistance of 3.9 m²K/GW for the entire epitaxial stack is achieved, three times lower than previous reports in various high-electron-mobility-transistor epi-structures. Gallium-nitride transistors demonstrate a record Johnson's Figure-of-Merit of 20.6 THz·V, an output-power-density of 42/20 W/mm at 8/30 GHz, representing a 30%/43% improvement over prior highest output-power-density for all X-/Ka-band transistors, respectively. This result manifests the implantation-induced nucleation strategy as a promising approach for advancing Gallium-nitride heteroepitaxy for RF electronics.