Abstract
The origin of photo-leakage current of zinc oxide thin-film transistors (ZnO TFTs) under light irradiation was investigated using a light shield technique. The irradiation position dependence revealed that the effect of light irradiation is much stronger near the source region in the channel than near the drain region. This can be explained by the enhanced carrier injection from the source electrode. The irradiation near the drain region, on the other hand, simply induced photocurrent, which is much smaller than the carrier injection on the source side. Therefore, completely transparent ZnO TFTs under visible light irradiation will be obtained, if the carrier injection from the source electrode is successfully suppressed.