Thermal Conductivity of β-Ga2O3 Thin Films Grown by Molecular Beam Epitaxy

β-Ga2O3 is considered as a promising material for future power electronic applications. In this work, we used time-domain thermoreflectance to measure the thermal conductivity and thermal boundary conductance (TBC) of thin films of β-Ga2O3 grown using molecular beam epitaxy (MBE) on c-Al2O3 (sapphire) and 4H-SiC substrates. One sample was 119 nm thick on sapphire, while the other sample was 81 nm thick on 4H-SiC. The Ga2O3 layer on c-sapphire presented a through-plane thermal conductivity of 3.2 ± 0.3 W/m-K with a Ga2O3/sapphire TBC of 155.6 ± 65.3 MW/m²-K. The thermal conductivity of the Ga2O3 layer on 4H-SiC was measured as 3.1 ± 0.5 W/m-K with a Ga2O3/SiC TBC of 141.8 ± 63.8 MW/m²-K. When compared with the thermal conductivity of films grown using pulsed-laser deposition from a previous study, thermal conductivity of layers grown by MBE show higher values, which suggests that the films grown by epitaxial method such as MBE can improve the thermal conductivity of thin films.