Abnormal thermal conductivity increase in β-Ga2O3 by an unconventional bonding mechanism using machine-learning potential

Abstract

β-Ga₂O₃, with its ultrawide band gap (∼4.9 eV) and high critical electric field, holds potential in power electronics but is limited by low thermal conductivity, which is critical to the performance and reliability because the high level of heat flux density induced by the extremely high levels of power density. Combining first-principles calculations, machine-learning potentials, and solving the phonon Boltzmann transport equation, we found that substituting octahedral-coordinated Ga with Al significantly enhances thermal conductivity from 100K to 800K. At room temperature, Al-substituted β-Ga2O3 achieves 38.91 W/mK, more than 2-fold that of pristine β-Ga₂O₃ (17.10 W/mK) and even higher than β-Al₂O₃ (30.52 W/mK). This enhancement, unusual due to the heavier atomic mass and mixed mass distribution, is rooted in suppressed anharmonic characteristics caused by reduced bonding strength inhomogeneity. Our results may inspire the rational design of materials with tailored thermal properties through chemical bonding mechanisms.