Unveiling the impact of four-phonon scattering on thermal transport properties of the bulk β-Ga2O3 and monolayer Ga2O3

In recent years, the role of four-phonon (4ph) scattering in thermal transport properties has been gradually revealed. However, the underlying scattering mechanisms of the bulk β-Ga₂O₃ and monolayer Ga₂O₃ remain unclear. Hence, we evaluate the effect of 4ph scattering on the thermal transport properties of the bulk β-Ga₂O₃ and monolayer Ga₂O₃ by utilizing first-principles calculations. It has been observed that the Young's modulus and lattice thermal conductivity (κ) of the bulk β-Ga₂O₃ are anisotropic, while the values of the monolayer Ga₂O₃ are isotropic. The κ of the bulk β-Ga₂O₃ along the three directions ([100], [010], and [001]) and monolayer Ga₂O₃ after adding 4ph scattering are decreased by 9.23%, 11.52%, 13.89%, and 29.24% at 300 K, respectively. Moreover, the effect of four-phonon scattering is more pronounced at the high temperature. Afterwards, based on the phonon behaviors, we can prove that the addition of 4ph scattering can increase the phonon scattering rate, decrease the phonon mean free path, and increase the phase space, which results in lower thermal conductivity. The findings can contribute to a better understanding of high-order phonon scattering mechanisms of the Ga₂O₃ materials.