High-Performance GaN-on-Diamond HEMTs Fabricated by Low-Temperature Device Transfer Process

We report recent progress on GaN-on-diamond high-electron-mobility transistors (HEMTs) fabricated by low-temperature device transfer. The devices were first fabricated on a GaN-on-SiC epitaxial wafer and were subsequently separated from the SiC and bonded onto a high-thermal-conductivity diamond substrate. The resulting GaN-on-diamond HEMTs demonstrated state-of-the-art electrical characteristics, including a maximum drain current density of 1.2A/mm and a peak transconductance of 390mS/mm. CW loadpull measurements at 10GHz gave an output power density of 11.0W/mm with 51% associated power-added efficiency. Thermal measurements showed the GaN-on-diamond devices maintained equivalent or lower junction temperatures than their GaN-on-SiC counterparts while dissipating 3 times higher power within the same active area. Such results demonstrate that the GaN device transfer process is capable of preserving transistor electrical performance while taking advantage of the excellent thermal properties of diamond substrates.