Top-gate thin-film transistors with amorphous ZnSnO channel layers prepared by pulsed plasma deposition

Abstract

In this study, an inorganic–organic hybrid thin-film transistor (TFT) with a top-gate structure is prepared using an inorganic ZnSnO film prepared via pulse plasma deposition as the channel layer and an organic polymethyl methacrylate film prepared by the solution method as the dielectric layer. The effect of oxygen pressure during the preparation of the ZnSnO channel layer and channel-layer structure on ZnSnO TFT performance was studied. The results show that increasing the oxygen pressure during the preparation process can effectively inhibit the formation of oxygen vacancies in ZnSnO and reduce the concentration of electron carriers in ZnSnO, resulting in a reduced off current and a positive shift of the threshold voltage (V_th) in the single-channel layer ZnSnO TFT. In addition, a high-resistivity ZnSnO layer (Lt; with a lower electron-carrier concentration) is embedded between the low-resistivity ZnSnO layer (Lb; with a higher electron-carrier concentration) and the dielectric layer to form a high-/low-resistivity double-channel-layer structure (Lt/Lb). By changing the thickness combination of Lt/Lb, the resistance of the channel layer and the number of carriers modulated by gate voltage in the channel layer can be optimized, thereby adjusting the device’s on current (affecting device mobility) and key energy consumption parameters (i.e., V_th and off current) to achieve independent control. Thus, the fabricated double-channel-layer ZnSnO TFT exhibits excellent performance: high mobility (3.28 cm²/Vs), positive V_th close to 0 V (0.48 V), and on-to-off current ratio of > 10⁵.