Synthesis of nano-diamond film on GaN surface with low thermal boundary resistance and high thermal conductivity

Joule self-heating is the main obstacle limiting the performance of GaN power devices. A nano-diamond (NCD) film for near-junction heat transfer has been approved as an effective approach to overcome this issue. In the present study, we developed a scheme to deposit a smooth NCD film with high thermal conductivity (TC) over the surface of GaN. First, a 10-nm Si3N4 was deposited as the protective layer of GaN, followed by electrostatic seeding to improve nucleation density and particle distribution uniformity. Second, argon and gradient methane gas were introduced to prepare the NCD film based on nucleation and the growth period. The resulting thickness of the NCD film was 150 nm with a roughness of about 20 nm. The thermal boundary resistance (TBReff) between GaN and NCD film was only 12.8 +/- 0.64 m2K/GW, whereas the TC of the NCD film was 200 +/- 40 W m- 1 K- 1, which was similar to the theoretical prediction. Thus, it could be inferred that the high crystallinity of the NCD film contributes to the low TBReff and high TC through the whole NCD layer.