Low-frequency noise in gas sensors: A review

Semiconductor-based gas sensors have been applied to a variety of applications, including environmental, safety, and health monitoring. Extensive efforts have been made to improve sensing performance outcomes, with the majority of these efforts focusing on the sensor response, sensitivity, and selectivity issues, mainly by optimizing the sensing materials and sensor structures. However, low-frequency noise (LFN), which has a considerable impact on the stability and reliability of sensors, has received far less attention in gas sensor research. In gas sensing applications, the noise in the sensing signal is determined by the LFN due to the slow reaction process. Thus, it is necessary to characterize the LFN in semiconductor-based gas sensors. This review article presents an overview of the LFN in semiconductor-based gas sensors. First, the history of LFN in gas sensor studies is explored briefly. Then, we discuss noise generation mechanisms in resistor-type, thin-film transistor-type, and horizontal floating-gate field-effect-transistor-type gas sensors. On the basis of this information, the signal-to-noise ratio, which determines the limit of detection, is examined, and the method to optimize the SNR in each sensor platform is discussed. Finally, LFN spectroscopy for selective gas detection is introduced, and its working principle is analyzed. This review article provides a foundation for understanding the LFN in semiconductor-based gas sensors and methods to control it based on application requirements.