Microstructures and rotational domains in orthorhombic ε-Ga^sub 2^O^sub 3^ thin films

• Published in: Japanese Journal of Applied Physics 2018-11, Vol.57 (11), p.115601
• Main Authors: Nishinaka, Hiroyuki, Komai, Hiroki, Tahara, Daisuke, Arata, Yuta, Yoshimoto, Masahiro
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition; Domains; Epitaxial growth; Gallium nitrides; Gallium oxides; Organic chemistry; Strontium titanates; Substrates; Thin films; Transmission electron microscopy; X-ray diffraction
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.57.115601

In this study, ε-Ga2O3 thin films were grown by mist chemical vapor deposition on a hexagonal (0001) GaN template and a cubic (111) SrTiO3 (STO) substrate. By analyzing the obtained X-ray diffraction (XRD) ȹ-scans, it was found that the ε-Ga2O3 epitaxial thin films grown on both GaN and STO exhibited an orthorhombic structure. In addition, a method was proposed to distinguish between hexagonal and orthorhombic structures on the basis of the relationships between the 2θ and χ angles for these structures, obtained from the XRD studies. Finally, a mechanism was discussed on the basis of angle relationships, where three rotational domains were observed for orthorhombic ε-Ga2O3 on GaN and STO. Transmission electron microscopy was then employed to determine whether the ε-Ga2O3 thin films on the GaN template and STO substrate consisted of columnar ε-Ga2O3 comprising small domains and intermediate layers between the ε-Ga2O3 film and the substrate.