Stronger role of four-phonon scattering than three-phonon scattering in thermal conductivity of III-V semiconductors at room temperature

Recent studies reveal that four-phonon scattering can be important in determining thermal conductivities of solids. However, these studies have been focused on materials where the thermal conductivity kappa is dominated by acoustic phonons, and the role of four-phonon scattering, although significant, is still smaller than that of three-phonon scattering at room temperature. In this work, taking A1Sb as an example for which optical phonons contribute significantly to the thermal conductivity under the three-phonon picture, we demonstrate that four-phonon scattering can be more important than three-phonon scattering as it diminishes optical phonon thermal transport and therefore significantly reduces the thermal conductivities of materials. Also, our calculations show that four-phonon scattering can diminish the isotope effect on kappa. Specifically, including four-phonon scattering reduces the room-temperature kappa of isotopically pure BAs from 3322 W/mK to 1721 W/mK, a 48% reduction. Four-phonon scattering reduces the room-temperature kappa of the isotopically pure and naturally occurring A1Sb by 70% and 50%, respectively, indicating that four-phonon scattering is more important than three-phonon scattering. The reductions for isotopically pure and naturally occurring cubic GaN are about 34% and 27%, respectively. For isotopically pure wurtzite GaN, the reduction is about 13% at room temperature and 25% at 400 K. These results provided important guidance for experimentalists for achieving high thermal conductivities in III-V compounds for applications in the semiconductor industry.