GaN thin films as gas sensors

A novel chemical sensor using GaN thin film has been proposed. Upon exposure to volatile organic compound (VOC) or combustible gases, such as butane, propane, and carbon monoxide, the electrical resistance of semiconducting GaN thin film was found to rapidly decrease, especially to alcohol (C2H5OH). When very thin Pt layer with a thickness of 3–5 nm was deposited, the GaN thin film not only exhibited good sensitivity and fast response to alcohol gas but also showed good linearity within the range of 500–12,000 ppm in the characteristics of the sensitivity to alcohol gas concentration. The interaction between the gas molecules and the GaN surface, and the gas-sensing mechanism were also investigated.