Low-voltage zinc-oxide thin-film transistors on a conventional SiO ₂ gate insulator grown by radio-frequency magnetron sputtering at room temperature

In this paper we present bottom-gate-type ZnO-based TFTs with low threshold voltages fabricated with a conventional SiO₂ gate insulator by radio-frequency (RF) magnetron sputtering at room temperature. The SiO ₂ is used as a gate insulator, and it is possible to achieve a low gate leakage current (<10 pA) by using this conventional SiO₂ oxide without new gate oxide materials. The ZnO film also has good uniformity and transparency, The ZnO TFTs operate in the enhancement mode with a threshold voltage of 2.5 V. A mobility of 0.018 cm²/(V's), an on/off ratio of about 10⁴, and a gate voltage swing of 1.7 V/decade are obtained. We successfully demonstrate that a ZnO TFT with comparable electrical characteristics can be fabricated by utilizing the conventional SiO² gate insulator. It is also possible to reduce the power consumption due to their low threshold voltage and low leakage current.