Gas sensing characteristics of low-powered dual MOSFET hydrogen sensors

A low-powered hydrogen sensitive dual-MOSFET device was designed, fabricated and evaluated for its ability to self compensate for electric signal degradation. The differential outputs between the sensing- and reference-FET were preserved within 3.74 μA to the thermal change (from 50 °C to 150 °C) due to the same dependence of the electrical characteristics. The proposed sensor design showed low power consumption (45.5 mW at 150 °C) by achieving complete heat isolation. Stable responses to H2 gas were observed over wide temperature ranges and the optimal point in the micro-heater operation was approximately 150 °C. (The highest sensitivity to 5000 ppm H2 gas was 111.17 μA with response and recovery times of 18 s and 19 s, respectively.) From the experimental results, the increased sensitivity to various H2 concentrations corresponded to the Langmuir relationship. The fabricated sensor device showed good gas selectivity toward CO and NH3 gases, and it showed a good performance in the facet of reproducible responses.