Modulating microstructure and thermal properties of diamond/SiNx/GaN multilayer structure by diamond growth temperature

Abstract

Numerous growth conditions affect thermal properties in diamond/SiNx/GaN multilayer structures, where diamond growth temperature is an important parameter and has not been adequately studied in the past. This article studies the relationship between the microstructure and thermal properties of diamond/SiNx/GaN multilayer structures under different diamond growth temperatures (740 °C–860 °C). The thermal boundary resistance of the diamond/GaN (TBReff, Dia/GaN) and thermal conductivity of the diamond (kDiamond) are measured using transient thermoreflectance (TTR). The lowest TBReff, Dia/GaN and highest kDiamond are achieved simultaneously at a growth temperature of 800 °C, and the difference in TBReff, Dia/GaN and kDiamond at different temperatures is up to 3–4 times. At the low growth temperature (740 °C), the thick transition layer is formed due to the insufficient ability of etching amorphous carbon and a significant carbon diffusion, resulting in significantly increased TBReff, Dia/GaN. At the high growth temperature (860 °C), the lattice distortion of GaN at the interface and the graphite phase in the transition layer contributed to the increase of TBReff, Dia/GaN. The thin diamond layer thickness and secondary nucleation result in low kDiamond except for 800 °C. The device simulation using the experimental kDiamond and TBReff, Dia/GaN at 800 °C predicts a 23 % reduction in maximum device temperature (Tmax) when the surface of GaN HEMTs is grown with a thin diamond layer.