Alloying Reversed Anisotropy of Thermal Transport in Bulk Al_0.5Ga_0.5N

Anisotropic heat transfer is crucial for advanced thermal management in nanoelectronics, optoelectronics, thermoelectrics, etc. Traditional approaches modifying thermal conductivity (κ) mostly adjust the magnitude but disregard anisotropy. Herein, by solving the Boltzmann transport equation from first principles, we report κ anisotropy modulation by alloying gallium nitride (GaN) and aluminum nitride (AlN). The alloyed Al_0.5Ga_0.5N demonstrates reversed κ anisotropy compared to the parent materials, where the preferred thermal transport direction shifts from cross-plane to in-plane. Moreover, the κ anisotropy (κ/κ) in the Al_0.5Ga_0.5N alloy is enhanced to 1.63 and 1.51 times that in bulk GaN and AlN, respectively, which can be further enhanced by increased temperature. Deep analysis attributes the alloying reversed κ anisotropy of Al_0.5Ga_0.5N to the structure distortion-driven phonon group velocity, as well as phonon anharmonicity. The alloying reversed κ anisotropy as reported in this study sheds light on future studies in advanced heat dissipation and intelligent thermal management.