Mobility enhancement of indium-gallium oxide via oxygen diffusion induced by a metal catalytic layer

In this study, the effects of a metal capping layer on indium-gallium oxide (IGO) films and associated TFTs were demonstrated. By introducing a Ta metal capping layer and a subsequent annealing process, IGO films are crystallized at the relatively low temperature of 250 °C which is suitable for low-cost flexible substrate such as PI. The Ta-induced IGO TFT shows significantly improved field-effect mobility from 29.3 (device without Ta layer) to 76.9 cm²/Vs. This improvement is due to the reduced number of defects which is consumed preferentially during the crystallization process by injected electron from the metal capping layer. Molecular dynamics calculations were performed in order to obtain theoretical insight into the inner-diffusions of atoms. Oxygen atoms near the interface region break their bonds with the metal cations of IGO and are attracted to Ta capping layer due to difference in the Gibbs free energy of formation, which should constitute the reason for its superior performance.