Scalable metal oxide functionalized GaN nanowire for precise SO2 detection

•Metal-oxide functionalized GaN nanowire-based devices were made by scalable top-down approach.•Photo-enabled gas sensing makes a significant reduction in operating power.•ZnO/GaN sensor was found to be the best candidate for precise SO2 detection.•Reliable and stable operation over wide range of temperature and humidity.•Principal component analysis (PCA) has been performed to address the cross-sensitive behavior of ZnO.