Effect of bias-enhanced nucleation on the microstructure and thermal boundary resistance of GaN/SiNx/diamond multilayer composites.

The low effective thermal boundary resistance (TBR eff) at the GaN/diamond interface is very important for the development of high-power, high-frequency and high-temperature GaN-on-diamond devices. The nucleation and growth of diamond are key processes for modulating the TBR eff. This work proposed the bias enhanced nucleation technique to adjust the nucleation of GaN/SiN x /diamond multilayer composites in the MPCVD process at different bias voltages (400–700 V), thereby adjusting TBR eff. Pulse bias is beneficial to a stable plasma environment and to obtain a complete GaN/diamond interface structure. The transient thermoreflectance characterization indicated that the GaN/SiN x /diamond multilayer composite prepared under 700 V bias nucleation condition had the lowest TBR eff (26 ± 10 m2K/GW), whereas the GaN/SiN x /diamond multilayer composite at 600 V bias had the highest TBR eff (83 ± 18 m2K/GW). The role of bias enhanced nucleation process in the TBR eff was systematically analyzed by electron microscopies (TEM and SEM) and Raman spectroscopy. The GaN/SiN x /diamond multilayer composite prepared at 600 V showed a thick mixed transition layer containing multiphase structures and rough interfaces due to efficient subsurface ion implantation, resulting in high TBR eff. In contrast, at 700 V, a thinner nucleation zone and smoother interface result in the lowest TBR eff. This work demonstrated the potential of adjusting TBR eff at the GaN/diamond interface by using bias enhanced nucleation technique to modulate the diamond nucleation and growth processes. [Display omitted] • GaN/SiN x /diamond multilayer composites were prepared using MPCVD technology. • Bias nucleation technology was proposed to adjust the diamond nucleation. • GaN/SiN x /diamond multilayer composites obtained at 700 V bias had the lowest TBR eff. • TBR eff at the GaN/diamond interface was realized by adjusting bias enhanced nucleation process. [ABSTRACT FROM AUTHOR]