Abstract
High-quality Ga2O3 thin films in the orthorhombic κ-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 2θ-ω scans, rocking curves, ϕ 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-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 κ-phase are a promising alternative for β-Ga2O3 layers in electronic and optoelectronic device applications.
Highlights
Heteroepitaxy of orthorhombic Ga2O3, mostly referred to as ε-Ga2O3 in the literature, was reported for pulsed-laser deposition10–13 (PLD), halide vapor phase epitaxy14,15 (HVPE), metal-organic chemical vapor deposition16–20 (MOCVD), metal-organic vapor phase epitaxy21 (MOVPE), atomic layer deposition,17 molecular beam epitaxy,22 plasma-assisted molecular beam epitaxy23 (PMBE), and mist CVD.24–28 Typically, α-Al2O3(00.1) is used as a substrate,10–12,17,18,20,22,29,30 but growth on 3C-SiC(001) and (111),17 6H-SiC(001),16 GGG(111),31 MgO(111) and YSZ(111),26 or GaN(0001), AlN(0001), and β-Ga2O3(2 ̄01)14 was reported as well
A tin-enriched surface layer on our thin films measured by depth-resolved photoelectron spectroscopy suggests surfactant-mediated epitaxy as a possible growth mechanism
Similarity of the structure of heteroepitaxial, orthorhombic Ga2O3 thin films to κ-Al2O3 was suggested by Matsuzaki et al.12 for PLD layers and proven for MOCVD layers by Cora et al
Summary
Heteroepitaxy of orthorhombic Ga2O3, mostly referred to as ε-Ga2O3 in the literature, was reported for pulsed-laser deposition10–13 (PLD), halide vapor phase epitaxy14,15 (HVPE), metal-organic chemical vapor deposition16–20 (MOCVD), metal-organic vapor phase epitaxy21 (MOVPE), atomic layer deposition,17 molecular beam epitaxy,22 plasma-assisted molecular beam epitaxy23 (PMBE), and mist CVD.24–28 Typically, α-Al2O3(00.1) is used as a substrate,10–12,17,18,20,22,29,30 but growth on 3C-SiC(001) and (111),17 6H-SiC(001),16 GGG(111),31 MgO(111) and YSZ(111),26 or GaN(0001), AlN(0001), and β-Ga2O3(2 ̄01)14 was reported as well. High-quality Ga2O3 thin films in the orthorhombic κ-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.
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