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

Abstract

We have developed light irradiation and applied voltage history sensors using amorphous In-Ga-Zn-O (-IGZO) thin-film transistors (TFTs) exposed to ozone annealing and fabricated under high oxygen pressure. These -IGZO TFTs have an interesting property; the Ids-Vgs characteristic shifts positively and becomes steep when gate voltage is applied, whereas it recovers the initial one with a small threshold voltage and a large subthreshold swing upon light illumination. Therefore, these -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 -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.