Conductometric nitrogen dioxide gas sensor based on gallium nitride quantum dots film

Gallium nitride (GaN) has some challenges for gas sensing, such as high detection lower limit (LOD) or complicated epitaxy of nanostructures. To address these issues, we exclusively designed a GaN quantum dots (QDs) film to enhance the gas interaction capability which fabricated by metal-organic chemical vapor deposition (MOCVD). The GaN QDs film gas sensor exhibits a low LOD (5 ppb) to nitrogen dioxide (NO2) at room temperature (RT), which has superior gas performance than other GaN-based sensors. The results of morphology and structure characterization manifest that many ultra-small QDs around 2 nm in diameter were stacked to form QDs of larger size, and confirm the existence of vacancies for the GaN QDs film. And the GaN QDs film sensor displays a ultra-high electron mobility of 1237.37 cm2 V−1s−1 at RT, which is greatly beneficial for gas sensing. The sensing mechanisms were analyzed based on its abundant active sites, ultrahigh carrier mobility, high surface energy and chemical activity, grain boundary barrier and good electrical conductivity. Moreover, the sensor processes high selectivity, repeatability, stability and reusability based on MOCVD technology which can realize precise control of structure and morphology, thus this sensor is expected to achieve rapid industrialization.