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

For beta-Ga2O3, only little information exists concerning the thermal properties, especially the thermal conductivity lambda. Here, the thermal conductivity is measured by applying the electrical 3 omega-method on Czochralski-grown beta-Ga2O3 bulk crystals, which have a thickness of 200 mu m and 800 mu mu m. At room temperature (RT), the thermal conductivity along the [100]-direction in Mgdoped electrical insulating and undoped semiconducting beta-Ga2O3 is confirmed as 13 +/- 1 Wm(-1)K(-1)for both crystals. The thermal conductivity increases for decreasing temperature down from 25 K to lambda (25 K)=(5.3 +/- 0.6) . 10(2)Wm(-1)K(-1). The phonon contribution of. dominates over the electron contribution below RT. The observed function lambda(T) is in accord with phonon-phonon-Umklapp scattering and the Debye model for the specific heat at T greater than or similar to 90 K which is about 0.1 times the Debye temperature theta(D). Here, a detailed discussion of the phonon-phonon-Umklapp scattering for T < theta(D) is carried out. The influence of point defect scattering is considered for T < 100 K.