Light irradiation and applied voltage history sensors using amorphous In-Ga-Zn-O thin-film transistors exposed to ozone annealing and fabricated under high oxygen pressure

We have developed light irradiation and applied voltage history sensors using amorphous In-Ga-Zn-O (oc-IGZO) thin-film transistor (TFTs) exposed to ozone annealing and fabricated under high oxygen pressure. These a-IGZO TFTs have an interesting property; the Ids-Vgs characteristic shifts positively and becomes steep when gate voltage is applied whereas it recover the initial one with a small threshold voltage and a large subthreshold swing upon light illumination. Therefore, these a-IGZO TFTs can be used as light irradiation history sensors; first, the gate voltage is applied to initialize the Ids-Vgs characteristic, next, the light is irradiated and finally, the Ids-Vgs characteristic is measured which depends on the light irradiation history. Moreover, these a-IGZO TFTs can be also used as applied voltage history sensors; first, the light is irradiated to initialize the Ids-Vgs characteristic, next, the gate voltage is applied and finally, the Ids-Vgs characteristic is measured which depends on the value or time of the applied voltage.