Phonon thermal transport in two-dimensional gallium nitride: Role of higher-order phonon–phonon and phonon–electron scattering

Two-dimensional gallium nitride (2D-GaN) has great potential in power electronics and optoelectronics. Heat dissipation is a critical issue for these applications of 2D-GaN. Previous studies have shown that higher-order phonon–phonon scattering has extremely strong effects on the lattice thermal conductivity (κlat) of 2D-GaN, with the fourth-order interatomic force constants (4th-IFCs) calculated using experienced atomic displacement in the finite difference method. In this work, it is found that the 4th-IFCs of 2D-GaN are quite sensitive to atomic displacement in the finite difference method. The effects of the four-phonon scattering can be severely overestimated with non-convergent 4th-IFCs. The κlat from three-phonon scattering is reduced by 65.6% due to four-phonon scattering. The reflection symmetry allows significantly more four-phonon processes than three-phonon processes. It was previously thought the electron–phonon interactions have significant effects on the κlat of two-dimensional materials. However, the effects of electron–phonon interactions on the κlat of both n-type and p-type 2D-GaN at high charge carrier concentrations can be neglected due to the few phonon–electron scattering channels and the relatively strong four-phonon scattering.