Tin-assisted heteroepitaxial PLD-growth of κ-Ga2O3 thin films with high crystalline quality

High-quality Ga2O3 thin films in the orthorhombic kappa-phase are grown by pulsed-laser deposition using a tin containing target on c-sapphire, MgO(111), SrTiO3(111), and yttria-stabilized ZrO2(111) substrates. The structural quality of the layers is studied based on the growth parameters employing X-ray diffraction 2 theta-omega scans, rocking curves, phi scans, and reciprocal space maps. Our layers exhibit superior crystalline properties in comparison to thin films deposited in the monoclinic beta-phase at nominally identical growth parameters. Furthermore, the surface morphology is significantly improved and the root-mean-squared roughness of the layers was as low as approximate to 0.5 nm, on par with homoepitaxial beta-Ga2O3 thin films in the literature. The orthorhombic structure of the thin films was evidenced, and the epitaxial relationships were determined for each kind of the substrate. A tin-enriched surface layer on our thin films measured by depth-resolved photoelectron spectroscopy suggests surfactant-mediated epitaxy as a possible growth mechanism. Thin films in the kappa-phase are a promising alternative for beta-Ga2O3 layers in electronic and optoelectronic device applications. (C) 2018 Author(s).