Super strain enhanced thermal conductivity of monolayer aluminum/gallium nitride (Al_<i>x</i>Ga_1−<i>x</i>N) alloys

The Al_<i>x</i>Ga_1-<i>x</i>N alloys play a crucial role as buffer layers in next-generation power electronic devices, where thermal transport is of great significance to performance stability and reliability. Typically, the Al_<i>x</i>Ga_1-<i>x</i>N alloys are often subjected to stress, stemming from various factors such as material preparation processes, temperature fluctuations during device operation, and external mechanical forces. Nevertheless, how to regulate stress and the impact of stress on the thermal transport properties of Al_<i>x</i>Ga_1-<i>x</i>N alloys remain unclear. In this paper, based on state-of-the-art first-principles calculations, we investigate the strain-regulated thermal transport properties of the monolayer Al_<i>x</i>Ga_1-<i>x</i>N alloys. Under tensile strain, the thermal conductivity of Al_<i>x</i>Ga_1-<i>x</i>N first increases and then decreases with increasing strain, presenting a non-monotonic behavior. The most significant enhancement of the thermal conductivity emerges in Al_0.5Ga_0.5N, where more than 20 times the pristine value is achieved at 10% strain. The fundamental mechanism underlying this anomalous response to strain of the thermal conductivity is traced back to the presence of lone pair electrons around the nitrogen atoms in Al_<i>x</i>Ga_1-<i>x</i>N. The interactions between the lone pair of electrons and the bonding electrons decrease with increasing strain, which gives rise to weakened phonon anharmonicity and super enhanced thermal conductivity. The findings revealed in this study indicate future directions for the efficient regulation of the thermal conductivity of advanced thermal functional materials and high-performance thermal management in electronics.