Effects of the thickness of the channel layer on the device performance of InGaZnO thin-film-transistors

InGaZnO thin-film-transistors (TFTs) with various channel thicknesses were fabricated with a bottom gate configuration on SiO₂/p-Si substrates at room temperature by radio frequency magnetron sputtering. The thickness of the InGaZnO channel layer ranged from 20 to 200nm and the width/length ratio of the channel was 10. In the channel layers with an electrical resistivity of ~10³Ωcm, TFTs with a 130nm thick layer showed the best performance, such as on/off-current ratio (~10⁷), channel field-effect mobility (7.2cm²/Vs) and subthreshold swing (0.7V/dec). In addition, the InGaZnO TFT device showed slight gate bias-induced hysteresis due to the small charge traps in the active layer and long-term reliability.