13. Mist Chemical Vapor Deposition 2

ε-Ga₂O₃ is one of the five polymorphs of Ga₂O₃, which has attracted considerable attention because it exhibits unique polarization and ferroelectric properties. In this chapter, we describe the growth of ε-Ga₂O₃ thin films via mist chemical vapor deposition (CVD). In the epitaxial growth of ε-Ga₂O₃ thin films, we demonstrated that various substrates allow ε-Ga₂O₃ growth via mist CVD because of the atomic arrangement between the surface of the substrate and the ε-Ga₂O₃ growth surface. Further, a method for distinguishing the hexagonal and orthorhombic structures of ε-Ga₂O₃ using X-ray diffraction (XRD) φ-scans was explained in detail. In our experiments, all ε-Ga₂O₃ thin films grown via mist CVD exhibited orthorhombic crystal structure, which permits rotational domains. Furthermore, the growth mechanism of these rotational domains was explained using the atomic arrangement of ε-Ga₂O₃ and the crystal structures of the substrates. Finally, bandgap engineering from 4.5 to 5.9 eV was demonstrated via mist CVD with the incorporation of In and Al.