Oxygen‐Regulated GaN‐Based Sensors Fabricated by MOCVD for Switchable Gas Detection: Exhaled Gas Smart Platform for Non‐Invasive Disease Detection

Miniaturized, easily integrated thin-film gas sensors with high consistency, stability, and suitability for mass production are crucial for non-invasive breath analysis. A series of GaN-based thin-film sensors with high stability and excellent sensing capabilities prepared by Metal-organic Chemical Vapor Deposition, in which the n-GaN sensor exhibited an ultra-low detection limit of 100 ppt for NO₂, and 2 ppb for NO, the InGaN sensors with different In composition manifest good response to reducing gases of NH₃ and TMA. The shift trend of selectivity for the sensors from oxidizing gases to reducing gase. can be attributed to the mutative relative content of the lattice oxygen/adsorbed oxygen ratio by adjusting the In composition, which is based on the in situ characterization results. The sensors exhibit excellent hydrophobicity, significantly enhancing their reliability in exhale gas sensing under high-humidity conditions. Response mapping model through mixed-gas training improved cross-sensor compatibility and enhanced model generalization. Herein an integrated multimodal sensor system combining a sensor array with a temperature and humidity sensor is proposed and developed alongside a dual-channel exhaled breath collection system. Utilizing a Time Sequence Analysis model, this integrated system enables non-invasive diagnosis of lung cancer patients.