III-Nitride Nanowire-Based Gas Sensors: From Material Design to Low-Temperature Sensing Performance

III-nitride nanowires (NWs), including gallium nitride (GaN) and its alloys, possess tunable direct band gaps, high electron mobility, and large breakdown voltages, making them highly promising for electronic and optoelectronic applications. In addition, their wide bandgap, efficient charge transport, mechanical robustness, and compatibility with CMOS technology make them strong candidates for high-performance sensing platforms. A gas sensor must meet certain qualities, such as low-temperature operation and high selectivity toward a particular gas, to prevent false signals caused by interference from other gases in the environment. Here, we review recent progress in room-temperature gas sensors based on III-nitride NW arrays, emphasizing defect-mediated gas adsorption, noble-metal decoration, integration with metal oxides and 2D materials, and light-activated sensing platforms. Detailed fabrication methods, sensing mechanisms, and strategies to enhance sensitivity, selectivity, and stability are discussed. Finally, current challenges and future design perspectives are highlighted to guide the development of practical, high-performance III-nitride NW gas sensors.