Abstract
For large-area electronic applications, the mechanism of the leakage current in oxide-semiconductor thin-film transistors (TFTs) has become a critical issue. In this work, the impact of the irradiation location on the photo-leakage current of zinc oxide (ZnO) TFTs is investigated. The photo-leakage current of the ZnO TFTs is not only dependent on the light irradiation but it is also dependent on the parasitic capacitance between the drain electrode and the floating gate metal. The photo-leakage current of the source-half irradiation TFT is larger than that of the drain-half irradiation TFT. To explain this phenomenon, the profile of the electric potential and the electron concentration is analyzed by two-dimensional device simulation. It is found that the floating gate metal plays the dominant role in the photo-leakage current. This research provides insight into TFT structure optimization and high-performance TFT process development.
Highlights
Oxide-semiconductor thin-film transistors (TFTs), such as ZnO TFTs1,2 and amorphous indium–gallium–zinc oxide (a-IGZO) TFTs,3,4 have been widely applied for large area displays and sensors
The photoleakage current of the ZnO TFTs is observed under light irradiation, especially under the blue light
The mechanism of the irradiation location on the photoleakage current of ZnO TFTs under light irradiation is investigated in detail
Summary
Oxide-semiconductor thin-film transistors (TFTs), such as ZnO TFTs1,2 and amorphous indium–gallium–zinc oxide (a-IGZO) TFTs, have been widely applied for large area displays and sensors. Our previous investigation and recent work demonstrated that the drain-to-source current was strongly related to the floating gate effect. It is crucial where the LS metal layer should be applied and about the floating gate effects. Kimura et al. found that the photo-leakage current of the sourcehalf irradiation TFT is larger than that of the drain-half irradiation TFT and explained that the Schottky barrier near the source region was narrowed by irradiation. It is found that the floating gate effect, i.e., the capacitive coupling between the floating LS metal layer and the drain electrode, plays the dominant role in the photo-leakage current. The electric potential profile and the electrical characteristics of the drain-half and the source-half irradiation TFTs are discussed
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