A Verilog-A Model for a Light-Activated Semiconductor Gas Sensor

Light activation is a demonstrated alternative to heating for promoting gas response in semiconductor gas sensors. After two decades of research, the underlying mechanisms behind their responses are still discussed, but experiments have shown consistent trends under different light conditions and gas concentrations. Based on these consolidated qualitative observations, we propose a phenomenological model that predicts quantitatively the resistance changes in light-activated gas sensors, exclusively based on a set of parameters that can be determined in advance, from dedicated experiments. It is a modular Verilog-A model that incorporates effects, such as photoconductivity, dynamic response to gases, irradiance influence on the sensitivity, and baseline drift. We validated the model with experimental data, showing it can predict observations in short and long timescales. We make its source-code fully available to the community, so that it can be used right away to help engineers to design interfaces for this kind of sensors, and it can be modified by peers to incorporate additional refinements.