Photoresponses of InSnGaO and InGaZnO thin-film transistors†
The photoresponses of thin-film transistors (TFTs) using indium-based oxide semiconductors have been studied. The devices were fabricated using amorphous InSnGaO (ITGO) or InGaZnO (IGZO) as the active semiconducting layer. ITGO and IGZO TFTs showed typical electrical characteristics including high on/off ratios and low off currents. Both devices induced photocurrents upon exposure to ultraviolet light due to their wide band gaps. However, the recovery time of IGZO TFTs was almost 1 h due to the slow recombination of trapped charges in the oxide semiconductors. In contrast, the recovery time of ITGO TFTs was significantly reduced compared to that of IGZO TFTs. We found that the origin of the shorter recovery time of ITGO TFTs was the low electron binding energy of indium, which was obtained by replacing zinc with tin and by increasing the composition ratio of indium. This method may be a useful way to fabricate high-speed optoelectronics based on oxide semiconductors.