In this study, the defects analysis of different thicknesses of ZnGa2O4 thin-film transistors grown on the sapphire substrate had been investigated. The thickness of ZnGa2O4 epilayer is controlled by growth time. The electrical properties and physical characteristics are strongly related to the thickness, which is also dependent on both crystallinity and the amount of oxygen vacancies in thin-film and independent on thin-film surface roughness. The study shows that crystallinity gets better and the oxygen vacancies which can be served as defect center also increase rapidly when the thickness is increasing. On the contrary, when the epilayer is thin, the film would be influenced by dislocation between ZnGa2O4 epilayer and the sapphire substrate. The results suggested that source of defects may come from crystallinity, oxygen vacancies, and dislocation between ZnGa2O4 and sapphire substrate. However, the lower resistance in ZnGa2O4 thin-film is not only due to better crystallinity but the more amount of oxygen vacancies especially. It is a trade-off between the conductivity and defects in ZnGa2O4 epilayer. The results also show that the high conductivity in ZnGa2O4 epilayer is mainly due to the amount of existing oxygen vacancies especially instead of crystallinity.
|