Significantly Enhanced Interfacial Thermal Conductance across GaN/Diamond Interfaces Utilizing Al_<i>x</i>Ga_1–<i>x</i>N as a Phonon Bridge

Improving the thermal conductance at the GaN/diamond interface is crucial for boosting GaN-based device performance and reliability. In this study, first-principles calculations and molecular dynamics simulations were employed to explore the interfacial thermal conductance of GaN/diamond interfaces with Al_<i>x</i>Ga_1-<i>x</i>N transition layers. The Al_<i>x</i>Ga_1-<i>x</i>N alloy exhibits a lower thermal conductivity than GaN, primarily due to enhanced anharmonic phonon scattering. However, for the interfacial thermal conductance at the GaN/diamond interface, we discovered that introducing an Al_<i>x</i>Ga_1-<i>x</i>N with a high Al concentration (<i>x</i> > 0.5) as a phonon bridge between GaN and diamond can significantly enhance the interfacial thermal conductance. In particular, it increases from 4.79 MW·m^-2 K^-1 to a maximum of 158 MW·m^-2 K^-1 at <i>x</i> = 0.75, surpassing the 152 MW·m^-2 K^-1 achieved by AlN. The Al_<i>x</i>Ga_1-<i>x</i>N alloy has been confirmed computationally as a more efficient phonon bridge, which can provide a valuable theoretical reference for experimentally investigating the thermal management and thermal design of high-power electronic devices based on the GaN/diamond interface.