Highly sensitive and stable MOSFET-type hydrogen sensor with dual FETs

A MOSFET gas sensor with platinum gate for hydrogen gas detection was designed, fabricated and characterized for sensing response and stability to outer environment. The dual-gate FET hydrogen sensor was integrated with a micro-heater and two Pt-gate FETs; a sensing device for hydrogen detection, and a reference device for electrical compensation. The identical output between the sensitive-FET and reference-FET was stable at the range from room temperature to 250°C due to the same temperature dependence of the current-voltage (I-V) characteristics. The Pt-FET sensor showed stable responses to hydrogen at a range of operation temperatures. The optimal operating temperature with 5,000 ppm H₂ was approximately 150°C at which the sensing response as drain current change was 0.112 mA. Also, the response and recovery times were 18 sec and 19 sec, respectively. The fabricated sensor showed low power consumption (45.5 mW at 150°C) by achieving complete heat isolation. The low-power MOSFET gas sensor can be suitable for applications in portable gas monitoring units and automobiles.