부산대학교 도서관

The multiple gate-voltage ( ${V}_{\text {g}}$ ) dependencies of the OFF-state photocurrent ( ${I}_{\mathrm {ph-{\scriptscriptstyle OFF}}}$ ) with increasing, decreasing, or being constant are observed in amorphous InZnO (a-IZO) thin-film transistors (TFTs) during reverse sweeps of ${V}_{\text {g}}$ from high to low values. This study provides a physical insight into the multiple ${V}_{\text {g}}$ dependencies by considering the joint effects of ${V}_{\text {g}}$ and the dynamic ionization of oxygen vacancy ( ${V}_{\text {O}}$ ) on the source-to-channel barrier that ultimately determines ${I}_{\mathrm {ph-{\scriptscriptstyle OFF}}}$ . When the photo-induced ionization of ${V}_{\text {O}}$ reaches a steady state during the reverse ${V}_{\text {g}}$ sweep, ${I}_{\mathrm {ph-{\scriptscriptstyle OFF}}}$ is primarily dominated by ${V}_{\text {g}}$ , resulting in a decreasing ${I}_{\mathrm {ph-{\scriptscriptstyle OFF}}}$ with ${V}_{\text {g}}$ . When the ionization of ${V}_{\text {O}}$ is far from reaching a steady state, ${I}_{\mathrm {ph-{\scriptscriptstyle OFF}}}$ is mainly affected by the increasing ${V}_{\text {O}}$ ionization, ${I}_{\mathrm {ph-{\scriptscriptstyle OFF}}}$ leading to an increasing with ${V}_{\text {g}}$ . An intermediate state exists, where the effects of ${V}_{\text {O}}^{{2}+}$ are comparable, resulting in an almost constant ${I}_{\mathrm {ph-{\scriptscriptstyle OFF}}}$ . The proposed mechanism is verified by experimentally measured results.