Significantly Enhanced\nInterfacial Thermal Conductance\nacross GaN/Diamond Interfaces Utilizing Al<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N as a Phonon Bridge

Improving the thermal conductance at the GaN/diamond\ninterface\nis crucial for boosting GaN-based device performance and reliability.\nIn this study, first-principles calculations and molecular dynamics\nsimulations were employed to explore the interfacial thermal conductance\nof GaN/diamond interfaces with Al<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N transition layers. The Al<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N\nalloy exhibits a lower thermal conductivity than GaN, primarily due\nto enhanced anharmonic phonon scattering. However, for the interfacial\nthermal conductance at the GaN/diamond interface, we discovered that\nintroducing an Al<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N with a high Al concentration (<i>x</i> > 0.5) as a phonon bridge between GaN and diamond can significantly\nenhance the interfacial thermal conductance. In particular, it increases\nfrom 4.79 MW·m<sup>–2</sup> K<sup>–1</sup> to a\nmaximum of 158 MW·m<sup>–2</sup> K<sup>–1</sup> at <i>x</i> = 0.75, surpassing the 152 MW·m<sup>–2</sup> K<sup>–1</sup> achieved by AlN. The Al<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N alloy has been confirmed\ncomputationally as a more efficient phonon bridge, which can provide\na valuable theoretical reference for experimentally investigating\nthe thermal management and thermal design of high-power electronic\ndevices based on the GaN/diamond interface.