Opposite atom dependence of isotope engineering of thermal conductivity in bulk and 2D GaN

Isotope engineering has been shown to be an effective means of regulating thermal conductivity. In this work, we studied the isotope engineering of thermal conductivity in bulk and 2D GaN, and diametrically opposite atom isotope dependence is found. That is, Ga isotope has a large effect (77%) on bulk GaN, while the effect of N isotope on the thermal conductivity is negligible. In 2D GaN, however, N isotope effect (20%) is more significant than that of Ga. Understanding of the different isotope dependence is achieved by deeper insight. Due to the relative magnitude of scattering rate, isotopic scattering influences the thermal conductivity of bulk and 2D GaN in different frequency regions, leading to the opposite atom dependence.