Evolution of electrical performance of ZnO-based thin-film transistors by low temperature annealing

The effects of post-annealing on performance of ZnO-based thin-film transistors (TFTs) fabricated at room temperature were investigated. It was observed that high-temperature annealing resulted in a large decrease in resistivity of the ZnO channel layer and caused a large off-state current for ZnO TFTs, while low-temperature annealing had little effect on the off-state current. The evolution of electrical performance of ZnO TFTs annealed at a lower temperature showed that the threshold voltage decreased greatly and the sub-threshold slope improved evidently without great change of the resistivity of the ZnO channel as the annealing time prolonged. The possible mechanism is that the traps have been removed without activating the donor defects in the ZnO channel layer.