Light Irradiation History Sensor Using Amorphous In-Ga-Zn-O Thin-Film Transistor Exposed to Ozone Annealing

We propose a light irradiation history sensor using an amorphous In-Ga-Zn-O ( -IGZO) thin-film transistor (TFT) exposed to ozone annealing at 300 . The -IGZO TFT has an interesting property. The Ids-Vgs characteristic shifts positively, and the subthreshold slope becomes steep when the gate bias is applied, whereas the Ids-Vgs characteristic shifts negatively and the subthreshold slope becomes gradual when the light is irradiated. Therefore, the -IGZO TFT can be used as a light irradiation history sensor by the following steps. First, the gate bias is applied to reset the Ids-Vgs characteristic. Next, the light is irradiated, and finally, the Ids-Vgs characteristic is measured, which depends on the light irradiation history.