The thermal conductivity of undoped, Sn-doped, and Fe-doped beta-Ga2O3 bulk crystals was measured by the 3 omega technique in the temperature range of 295-410 K. A unique approach for extracting the thermal conductivity along the lateral and transverse heat flow directions was used in order to determine the thermal conductivity along different crystallographic directions. The data analysis at room temperature confirmed the expected anisotropy of the thermal conductivity of beta-Ga2O3, revealing the highest value of similar to 29 W/m K in the [010] direction. The thermal conductivity of the Sn-doped and Fe-doped beta-Ga2O3 samples was found to be lower than that of the undoped samples due to the enhanced phonon-impurity scattering contribution, which reduces the thermal conductivity. This tendency was maintained for the thermal conductivity at elevated temperatures. The thermal conductivity in all samples decreased with increasing temperature, but the slope of the temperature dependence was found to depend on both the doping and the crystallographic orientation. Published by AIP Publishing.
Funding Agencies|NSF [CBET-1336464, DMR-1506159]; Swedish Energy Agency [P39897-1]