Effect of Source/Drain Electrodes on the Electrical Properties of Silicon⁻Tin Oxide Thin-Film Transistors

Ultra-high definition displays have become a trend for the current flat plane displays. In this study, the contact properties of amorphous silicon⁻tin oxide thin-film transistors (a-STO TFTs) employed with source/drain (S/D) electrodes were analyzed. Ohmic contact with a good device performance was achieved when a-STO was matched with indium-tin-oxide (ITO) or Mo electrodes. The acceptor-like densities of trap states (DOS) of a-STO TFTs were further investigated by using low-frequency capacitance⁻voltage (C⁻V) characteristics to understand the impact of the electrode on the device performance. The reason of the distinct electrical performances of the devices with ITO and Mo contacts was attributed to different DOS caused by the generation of local defect states near the electrodes, which distorted the electric field distribution and formed an electrical potential barrier hindering the flow of electrons. It is of significant importance for circuit designers to design reliable integrated circuits with SnO₂-based devices applied in flat panel displays.