An investigation of the different charge trapping mechanisms for SiN _x and SiO _2 gate insulator in a-IGZO TFTs

摘要

We investigated the threshold voltage (V _(TH)) shifts of a-IGZO thin-film transistors (TFTs) in which the gate-insulator was either SiO _2 or SiN _x. The V _(TH) shift of the TFT using a SiO _2 obeyed the stretched-exponential time model, and increased sharply according to temperature increase, whereas the SiN _x device obeyed the logarithmic time model, and exhibited weak temperature dependence. We found that an inter-layer formed between the IGZO and the SiN _x, whose existence can be the origin of poor bias stability and the different V _(TH) shift behavior in a-IGZO TFTs because the inter-layer accelerates the direct charge injection from the channel.