Review—Semiconductor Materials and Devices for Gas Sensors

Gas sensors are frequently used for detecting toxic gases and vapors for environmental control, industrial monitoring and household safety. Semiconductor conductivity can be modified by doping or fine-tuned by applying an electric or magnetic field in an ultra-wide range (10 −7 S cm −1 to 10 2 S cm −1 ). The conduction of semiconductor is significantly raised or reduced upon the exposure to external conditions, such as temperature variation, light, heat, mechanical stress or chemicals. Thus, semiconductors are excellent materials for sensors and the device structures are critical for sensing performance. The commonly used semiconductors materials include Si, Ge, III–V, and metal oxide semiconductors. Recently carbon-based materials gain signification attention due to their unique electrical, optical and mechanical properties. There are two major semiconductor gas sensors: resistor-based and FET-based sensors. In this review, the semiconductor materials, sensor device structure as well as gas sensing mechanisms will be systematically categorized, described and explored, with the focus on metal oxides, GaN, SiC, 2D-TMD and carbon-based gas sensors. The recent progress in new semiconductor gas sensors will be thoroughly reviewed and summarized, with a hope to show the trend in semiconductor gas sensor technology.