Tunneling condition at high Schottky barrier and ambipolar transfer characteristics in zinc oxide semiconductor thin film transistor

• Ohmic contact has no potential barrier.
• Schottky contact has a potential barrier.
• Poole–Frenkel (PF) contact has a very high potential barrier.
• There are a trapping by drift currents in channels and a tunneling by diffusions in depletion as insulators.
• High quality of insulators is essential for a PF emission.

This study investigates the behavior of SiOC as gate dielectric materials for zinc-based oxide semiconductor thin film transistors (TFTs). The SiOC with a high potential barrier due to a low ionic energy at a Poole–Frenkel (PF) contact was suitable for use as a gate dielectric material to support tunneling in ZnO/SiOC TFTs. The performance of the ZnO TFTs for the low-polarization SiOC improved by introducing a direct tunneling phenomenon in the minority carriers of the SiOC depletion layer due to the decrease in the activation energy and the very high Schottky barrier (SB) of the SiOC material. PF emission was achieved at a non-polar SiOC with a high SB, and the mobility-stability of the TFTs with the PF contact dramatically improved. The TFT of the PF contact with a high SB was free from a shift in the threshold voltage with a decrease of the drain voltage.

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