Dissimilar thermal transport properties in κ-Ga2​O3​ and
β-Ga2​O3​ revealed by machine-learning homogeneous nonequilibrium
molecular dynamics simulations
The lattice thermal conductivity (LTC) of Ga2​O3​ is an important
property due to the challenge in the thermal management of high-power devices.
We develop machine-learned neuroevolution potentials for single-crystalline
β-Ga2​O3​ and κ-Ga2​O3​, and apply them to perform
homogeneous nonequilibrium molecular dynamics simulations to predict their
LTCs. The LTC of β-Ga2​O3​ was determined to be 10.3 ± 0.2 W/(m
K), 19.9 ± 0.2 W/(m K), and 12.6 ± 0.2 W/(m K) along [100], [010], and
[001], respectively, aligning with previous experimental measurements. For the
first time, we predict the LTC of κ-Ga2​O3​ along [100], [010], and
[001] to be 4.5 ± 0.0 W/(m K), 3.9 ± 0.0 W/(m K), and 4.0 ± 0.1
W/(m K), respectively, showing a nearly isotropic thermal transport property.
The reduced LTC of κ-Ga2​O3​ versus β-Ga2​O3​ stems from
its restricted low-frequency phonons up to 5 THz. Furthermore, we find that the
β phase exhibits a typical temperature dependence slightly stronger than
∼T−1, whereas the κ phase shows a weaker temperature
dependence, ranging from ∼T−0.5 to ∼T−0.7.Comment: 8 pages, 7 figure