We have structurally evaluated β-Ga2O3 crystals grown by edge-defined film-fed growth process using etch pitting, focused ion beam scanning ion microscopy, transmission electron microscopy, and related techniques. We found three types of defects: arrays of edge dislocations corresponding to etch pit arrays on -oriented wafers, platelike nanopipes corresponding to etch pits revealed on the (010)-oriented wafers, and twins including twin lamellae.

Herein, single-domain κ-Ga2O3 thin films were grown on FZ-grown ε-GaFeO3 substrates via a step-flow growth mode. The ε-GaFeO3 possessing the same crystal structure and similar lattice parameters as those of the orthorhombic κ-Ga2O3 facilitated the growth of κ-Ga2O3 thin films, as observed by the X-ray diffraction (XRD) analysis. Furthermore, the surface morphologies of the κ-Ga2O3 thin films exhibited a step–terrace and atomically flat structure. XRD φ-scan and transmission electron microscopy with selected area electron diffraction revealed that there is no occurrence of in-plane rotational domains in the κ-Ga2O3 thin films on ε-GaFeO3 substrates and that the κ-Ga2O3 thin film comprised a single domain. TEM analysis revealed that there were no clear dislocations in the observation area. Moreover, high-resolution TEM observation showed that the atomic arrangements of the film and the substrate were continuous without the presence of an intermediate layer along the growth direction and were well-aligned in the in-plane direction.

We demonstrated the growth of a single-domain κ-Ga2O3 thin film on ε-GaFeO3 by using an organic-free compound as a precursor for mist chemical vapor deposition. X-ray diffraction analysis revealed that an 87-nm-thick κ-Ga2O3 thin film was grown almost coherently with slight lattice relaxation. The surface morphology of the κ-Ga2O3 thin film exhibited a step-terrace structure without island growth. Furthermore, plan-view TEM observations revealed that the κ-Ga2O3 thin film grown on ε-GaFeO3 had a single domain, whereas the previously reported κ-Ga2O3 thin film grown on AlN template had a domain structure.

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