Progress towards III-nitrides HEMTs on free-standing diamond substrates for thermal management

In this paper, we discuss the progress in the application of silicon‐on‐diamond (SOD) and chemically vapour deposited (CVD) diamond wafers as an alternative solution to silicon and silicon carbide (SiC) substrates to enhance heat dissipation away from the active region of AlGaN/GaN high electron mobility transistors (HEMT) while decreasing thermal degradation due to thermal effects. The superior thermal conductivity and insulating properties of polycrystalline diamond (8–15 Wcm/K) free‐standing wafers have demonstrated certain advantages, mostly evident in the device performance and reliability. Two unique diamond growth applications engineered by sp3 Diamond Technologies Inc., and Group4 Labs Inc., are discussed and device performance data is presented from early attempts to our most current device research efforts. As single‐crystalline diamond wafers (∼20 Wcm/K) become more accessible and affordable, it is expected to see significant improvement over the current state of this technology. Group4 employs an atomic bonding process of the AlGaN/GaN layers onto a polycrystalline CVD diamond wafer while sp3 grows the AlGaN/GaN layers on a thin silicon template layer which covers the diamond.