Insight into the evolution of electrical properties for Schottky-barrier IGZO thin-film transistors with Cu-based Schottky contacts

In this work, we performed systematic electrical characterization and analysis of indium–gallium–zinc oxide (IGZO) Schottky-barrier thin-film transistors (SBTFTs) with different Cu-based Schottky contact structures. It was found that the Schottky barrier height (Φ_B) between the IGZO layer and the Cu electrode could be modulated notably by changing the thickness of the AlO_x tunnel layer, and the variation in Φ_B significantly changed the saturation drain current (I_dsat) of the IGZO SBTFTs based on the Schottky contacts but only had a minor influence on the saturation voltage (V_dsat) of the devices. Furthermore, Cu/Al stacked source/drain electrodes and silicon nitride (SiN_x) passivation were employed to tailor the contact resistance and channel resistance of the IGZO SBTFTs, which led to an increase in I_dsat and a variation in V_dsat. A universal resistance–capacitance network model was proposed to explain the observed evolution of V_dsat of the SBTFTs with different device structures. This work provides meaningful insight into developing low-cost metal oxide SBTFTs with tailored device performances.