Yasuyoshi Nagai

Thermal management is critical in contemporary electronic systems, and integrating diamond with semiconductors offers the most promising solution to improve heat dissipation. However, developing a technique that can fully exploit the high thermal conductivity of diamond, withstand high‐temperature annealing processes, and enable mass production is a significant challenge. In this study, the successful transfer of AlGaN/GaN/3C‐SiC layers grown on Si to a large‐size diamond substrate is demonstrated, followed by the fabrication of GaN high electron mobility transistors (HEMTs) on the diamond. Notably, no exfoliation of 3C‐SiC/diamond bonding interfaces is observed even after annealing at 1100 °C, which is essential for high‐quality GaN crystal growth on the diamond. The thermal boundary conductance of the 3C‐SiC‐diamond interface reaches ≈55 MW m −2 K −1 , which is efficient for device cooling. GaN HEMTs fabricated on the diamond substrate exhibit the highest maximum drain current and the lowest surface temperature compared to those on Si and SiC substrates. Furthermore, the device thermal resistance of GaN HEMTs on the diamond substrate is significantly reduced compared to those on SiC substrates. These results indicate that the GaN/3C‐SiC on diamond technique has the potential to revolutionize the development of power and radio‐frequency electronics with improved thermal management capabilities.