Channel thickness effect on the performance of amorphous SiZnSnO semiconductor thin-film transistor with metal capping structure

Thin-film transistors (TFTs) based on amorphous oxide semiconductors have proven successful in the display industry and have recently expanded their applications. Consequently, attention to high-performance amorphous oxide based TFTs has significantly increased. In this study, we investigate the effect of the active channel-layer thickness on the performance of metal-capping (MC) a-SiZnSnO (a-SZTO) TFTs, where the MC layer improves the electrical properties and stability despite its simplicity. At the thinnest channel thickness of 6 nm, the mobility increases the most, reaching 106.79%. Subsequently, as the thickness of a-SZTO increases, the mobility increase gradually decreases. At the thickest 120 nm, the mobility increase is 59.94%, almost half the increase observed at 6 nm. The improved electrical properties of the MC layer structure are largely attributed to the injected electrons resulting from the additional bent band in the back-channel region where the MC layer is present. Different channel thicknesses have varying effects on the injected electrons. These results indicate that, in addition to the previously reported effect of the MC layer on electrode type, the thickness of the channel also plays a significant role.