Lattice thermal conductivity in β-Ga2O3 from first principles

The lattice thermal conductivity for bulk β-Ga2O3 is computed from the phonon Boltzmann transport equation using first-principles methods to obtain scattering rates. Force constants for both the second and third order potential interactions are computed with a real-space finite-displacement approach. Phonon band structures as well as anharmonic properties are then computed and used to calculate the bulk thermal conductivity tensor κ, for temperatures ranging from 25 K to 1050 K. The calculated conductivity tensor components and analytic fits to their temperature dependences are elaborated. We compare our results with available data and show good agreement with experimentally observed values. Decomposing κ into mode contributions reveals that optical phonon modes contribute significantly to the overall thermal conductivity, as much as 44% at 300 K in the 010 direction, which differs from previous interpretations of experimentally observed thermal conductivity tensor anisotropy.