Systematic Investigation of Growth and Properties of Ga2O3 Films on C-Plane Sapphire Substrates Prepared by Plasma-Assisted Molecular Beam Epitaxy

Abstract

We investigated the growth and properties of Ga2O3 films on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). Growth parameters generally affect the structure and properties of films. In growing Ga2O3 films on sapphire substrates by PAMBE, source flux and growth temperature are main key factors and effects of those on growth behaviors, surface morphology, crystallinity, structural quality, and optical properties have been investigated by systematic experimental design using various characterization methods including reflection high energy electron diffraction, atomic force microscope, X-ray diffraction, transmission electron microscopy etc. The source flux strongly affected growth rate of Ga2O3 films by PAMBE, and the growth temperature strongly affected surface morphology and structural properties. The orientation relationship was determined to be β-Ga2O3 //Al2O3(0001) and β-Ga2O3[010]//Al2O3[]. However, the β-Ga2O3 films were not single crystalline but showed six-fold in-plane symmetry with six rotational domain structures. The detailed rotational domain structures were investigated by transmission electron diffraction analysis. The smooth surface with the RMS value of 0.95 nm can be obtained at growth temperature of 800 °C. All the grown β-Ga2O3 films are highly transparent and the optical bandgaps were 4.79–4.89 eV.