Temperature-dependent thermal conductivity and diffusivity of a Mg-doped insulating β -Ga 2 O 3 single crystal along [100], [010] and [001]

Abstract The monoclinic crystal structure of β - Ga 2 O 3 leads to significant anisotropy of the thermal properties. The 2 ω -method is used to measure the thermal diffusivity D in [010] and [001] direction respectively and to determine the thermal conductivity values λ of the [100], [010] and [001] direction from the same insulating Mg-doped β - Ga 2 O 3 single crystal. We detect a temperature independent anisotropy factor of both the thermal diffusivity and conductivity values of D [ 010 ] / D [ 001 ] = λ [ 010 ] / λ [ 001 ] = 1.4 ± 0.1 . The temperature dependence is in accord with phonon–phonon-Umklapp-scattering processes from 300 K down to 150 K. Below 150 K point-defect-scattering lowers the estimated phonon–phonon-Umklapp-scattering values.