Tin-assisted heteroepitaxial PLD-growth of κ -Ga 2 O 3 thin films with high crystalline quality

Abstract

High-quality Ga 2 O 3 thin films in the orthorhombic κ-phase are grown by pulsed-laser deposition using a tin containing target on c-sapphire, MgO(111), SrTiO 3 (111), and yttria-stabilized ZrO 2 (111) substrates. The structural quality of the layers is studied based on the growth parameters employing X-ray diffraction 2θ-ω scans, rocking curves, scans, and reciprocal space maps. Our layers exhibit superior crystalline properties in comparison to thin films deposited in the monoclinic β-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 0.5 nm, on par with homoepitaxial β-Ga 2 O 3 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 κ-phase are a promising alternative for β-Ga 2 O 3 layers in electronic and optoelectronic device applications.