Macroscopic analysis and design of Si HFGFET gas sensor for sensitive gas detection

•The effect of structure geometry of HFGFET gas sensors on their gas sensing performance is investigated.•Using both TCAD device simulation and actual gas sensing measurement, the macroscopic analysis on HFGFET gas sensors is performed.•Utilizing a simplified equivalent circuit of HFGFET gas sensors, we define a new parameter representing a magnitude of gas sensitivity.•Gas sensing performance of HFGFET gas sensors is affected by the antenna effect and transconductance.