Temperature-dependent thermal conductivity in Mg-doped and undoped β-Ga2O3 bulk-crystals

Abstract. For β-Ga2O3 only little information exist concerning the thermal properties, especially the thermal conductivity λ. Here, the thermal conductivity is measured by applying the electrical 3ω-method on Czochralski-grown β-Ga2O3 bulk crystals, which have a thickness of 200 µm and 800 µm. At room temperature the thermal conductivity along the [100]-direction in Mg-doped electrical insulating and undoped semiconducting β-Ga2O3 is confirmed as 13 ± 1 Wm−1K−1 for both crystals. The thermal conductivity increases for decreasing temperature down to 25 K to λ(25 K) = (5.3±0.6) ·102 Wm−1K−1. The phonon contribution of λ dominates over the electron contribution below room temperature. The observed function λ(T) is in accord with phonon-phonon-Umklapp scattering and the Debye-model for the specific heat at T & 90 K which is about 0.1 fold of the Debye-temperature θD. Here a detailed discussion of the phonon-phonon-Umklapp scattering for T < θD is carried out. The influence of point defect scattering is considered for T < 100 K. ar X i