Identification of ammonia and carbon monoxide based on the hysteresis of a gas-sensitive SiC field effect transistor

In this work gate bias cycled operation (GBCO) is used on a gas-sensitive SiC field effect transistor (“GasFET”) to increase the sensitivity and selectivity. Gate bias ramps introduce strong hysteresis in the sensor signal. The shape of this hysteresis is shown to be an appropriate feature both for the discrimination of various gases (NH3, CO, NO, CH₄) and also different gas concentrations (250 and 500 ppm). The shape is very sensitive to ambient conditions. Thus, the influence of oxygen concentration and relative humidity as well as sensor temperature is investigated and reasons for the observed signal changes are discussed.