Growth and characteristics of β-Ga2O3 thin films on sapphire (0001) by low pressure chemical vapour deposition

Monoclinic beta phase Ga2O3 has been considered as a promising candidate for next generation radio frequency and high-power devices because of its ultrawide bandgap and high breakdown field. The development of epitaxial growth techniques and the synthesis of high quality beta-Ga2O3 thin films are crucial for the device applications. In this work, the heteroepitaxial beta-Ga2O3 thin films were grown on sapphire (0001) substrates by low pressure chemical vapor deposition. The influence of growth parameters such as the source/substrate temperatures, the oxygen/Ar gas flow rates, and the surface morphology of substrate on the resultant crystallinity and surface roughness of the beta-Ga2O3 films were investigated. The beta-Ga2O3 heteroepitaxial layer on sapphire exhibits an RMS roughness of 1.82 nm, an XRD rocking curve of 1.18 degrees, and a growth rate of 0.72 mu m/h. The beta-Ga2O3 film grown on the buffer layer exhibit a smoother surface, whereas the chemical etching and annealing lead to an improved crystallinity and a rough surface. However, there is a trade-off between the crystallization and the surface roughness.