NOx gas sensors based on layer-transferred n-MoS2/p-GaN heterojunction at room temperature: Study of UV light illuminations and humidity

Transition metal dichalcogenides (TMDs) have gained extensive interest due to their phenomenal optoelectrical and electrochemical properties. Recently, TMDs are used as one of the auspicious materials for the chemical gas sensor application owing to their low operating temperatures. In this study, we developed room-temperature nitrogen oxide (NOx) gas sensors using n-MoS2/p-GaN hybrid-structure made by layer-transfer technique. The device response to NO2, NO, NH3, H-2, H2S, and CO target gases under UV illumination at 27 degrees C has been evaluated. The n-MoS2/p-GaN heterostructure was noticed to have significant selectivity to NO2 gas compared to pristine p-GaN film with particularly high response of 98.42 % to 50 ppm of NO2 under UV illumination. Under UV light, MoS2/p-GaN heterostructure works effectively at a lower temperature than in dark. Further, by using photonic energy we also boosted NO2 response and made recovery signal of device faster. Our results divulged that temperature significantly influenced the response of the heterostructure and it escalated from 47.48 % to 148.81 % to 50 ppm of NO2 in the temperature range of 27-150 degrees C. The heterostructure sensor showed slight degradation (less than 15 %) to NO2 at 60 % of relative humidity. The proposed device seems to be a good candidate for room temperature gas sensing applications.