Ultra-High Sensitive NO₂ Gas Sensor Based on Tunable Polarity Transport in CVD-WS₂/IGZO p-N Heterojunction

In this work, a thin-film transistor gas sensor based on the p-N heterojunction is fabricated by stacking chemical vapor deposition-grown tungsten disulfide (WS 2 ) with a sputtered indium–gallium–zinc-oxide (IGZO) film. To the best of our knowledge, the present device has the best NO 2 gas sensor response compared to all the gas sensors based on transition-metal dichalcogenide materials. The gas-sensing response is investigated under different NO 2 concentrations, adopting heterojunction device mode and transistor mode. High sensing response is obtained of p-N diode in the range of 1–300 ppm with values of 230% for 5 ppm and 18 170% for 300 ppm. On the transistor mode, the gas-sensing response can be modulated by the gate bias, and the transistor shows an ultrahigh response after exposure to NO 2, with sensitivity values of 6820% for 5 ppm and 499 400% for 300 ppm. Interestingly, the transistor has a typical ambipolar behavior under dry air, while the transistor becomes p-type as the amount of NO 2 increases. The assembly of these results demonstrates that the WS 2 /IGZO device is a promising platform for the NO 2 -gas detection, and its gas-modulated transistor properties show a potential application in tunable engineering for two-dimensional material heterojunction-based transistor device.