Incorporation of indium into ε-gallium oxide epitaxial thin films grown via mist chemical vapour deposition for bandgap engineering

Epitax at epsilon-gallium oxide (Ga2O3) thin films incorporated with In were successfully grown by mist chemical vapour deposition (CVD) on c-plane sapphire substrates for bandgap tuning. In was successfully incorporated into epitaxial epsilon-(ln(x)Ga(1-x))(2)O-3 films at an In composition of x = 0.2 without inducing phase separation. Phase separation originated from the (400) bixbyite structure of (ln(x)Ga(1-x))(2)O-3 when x > 0.2. The solubility limit of In incorporated into epsilon-Ga2O3 on sapphire substrates via mist CVD was therefore x = 0.2. Transmission electron microscopy measurements revealed that epsilon-(ln(x)Ga(1-x))(2)O-3 consisted of polycrystalline phases observed in the interface of the sapphire substrate and epsilon-phases located above the polycrystalline phase. The pole figure of epsilon-(ln(x)Ga(1-x))(2)O-3 thin films revealed that the epitaxial relationship between the epsilon-(ln(x)Ga(1-x))(2)O-3 thin film and the alpha-Al2O3 substrate is (001) epsilon-(ln(x)Ga(1-x))(2)O-3 [130]parallel to(0001) alpha-Al2O3 [11-20]. The optical bandgap of the epsilon-(ln(x)Ga(1-x))(2)O-3 thin films was tuned from 4.5 to 5.0 eV without inducing phase separation.