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 (WS2) with a sputtered indium–gallium–zinc-oxide
(IGZO) film. To the best of our knowledge, the present device has
the best NO2 gas sensor response compared to all the gas
sensors based on transition-metal dichalcogenide materials. The gas-sensing
response is investigated under different NO2 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 NO2, 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 NO2 increases. The assembly of these results
demonstrates that the WS2/IGZO device is a promising platform
for the NO2-gas detection, and its gas-modulated transistor
properties show a potential application in tunable engineering for
two-dimensional material heterojunction-based transistor device.
We developed an AlGaN/GaN high electron mobility transistor (HEMT) sensor with a tungsten trioxide (WO 3 ) nano-film modified gate for nitrogen dioxide (NO 2 ) detection. The device has a suspended circular membrane structure and an integrated micro-heater. The thermal characteristic of the Platinum (Pt) micro-heater and the HEMT self-heating are studied and modeled. A significant detection is observed for exposure to a low concentration of 100 ppb NO 2 /N 2 at ∼300 • C. For a 1 ppm NO 2 gas, a high sensitivity of 1.1% with a response (recovery) time of 88 second (132 second) is obtained. The effects of relative humidity and temperature on the gas sensor response properties in air are also studied. Based on the excellent sensing performance and inherent advantages of low power consumption, the investigated sensor provides a viable alternative high performance NO 2 sensing applications. It is suitable for continuous environmental monitoring system or high temperature applications.
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