Temperature-corrected full-band Monte Carlo simulation of phonon transport mechanism in 2D GaN

Two-dimensional gallium nitride (2D GaN) is a direct bandgap material with high quantum efficiency, making it ideal for thermoelectric applications, optoelectronics, and high-frequency devices. This paper thoroughly explores the phonon dynamics and thermal conductivity properties of 2D GaN. Density functional theory (DFT) combined with relaxation time approximation (RTA) is used to adjust phonon relaxation times and specific heat capacities for multiple temperatures, with an exploration of how temperature influences phonon scattering rates. The results suggest that 2D GaN is extremely sensitive to temperature variations during thermal transport. As the temperature increases, there is a significant decrease in the relaxation time of phonons, which makes scattering more likely. Remarkably, at elevated temperatures, the heat capacity of high-frequency optical phonons approaches that of acoustic phonons, exhibiting a higher degree of temperature sensitivity. In addition, the thermal conductivity of 2D GaN in the suspended state is compared with that of the silicon-based support state and it is found that interfacial scattering effects significantly reduce the thermal conductivity of the silicon-based support state. It is found that the contribution of the FA branch of 2D GaN on a silicon substrate surface to the thermal conductivity is significantly reduced, unlike the mechanism in conventional semiconductor materials. Further analysis shows that due to the strong interaction between Si substrate and 2D GaN, the cumulative distribution function of the FA branch is significantly reduced, which in turn leads to the anomaly of the FA branch. Based on the above analysis, an all-band phonon Monte Carlo (TFMC) method with temperature correction is proposed in this study, which combines the phonon Boltzmann transport equation and first principles to analyze the heat transport behavior of 2D GaN at different temperatures, and further reveals the influence mechanism of substrate action on its heat transport. The findings serve as a valuable reference for choosing substrate materials and improving heat transfer in nanomaterial devices. © 2024 Elsevier Masson SAS