Chapter Twelve - Dynamic operation of semiconductor sensors

Abstract

Semiconductor gas sensors not only offer high sensitivity and robust long-term performance but also suffer from poor selectivity. A powerful approach to improve selectivity is based on dynamic operation. The most relevant and widely studied method is temperature modulation which can be applied to metal oxide semiconductor (MOS) gas sensors, pellistor-type sensors, and gas-sensitive field-effect transistors (GasFETs). Other dynamic operating modes are based on field effect/polarization and on optical excitation. All methods change the equilibrium on the sensor surface and thus provide additional information especially during nonequilibrium states. The generic term dynamic operation implies the active variation of a control parameter by the sensor electronics allowing application-specific optimization of the sensor system performance. This chapter discusses dynamic operating modes for MOS and GasFET sensors to show that not only selectivity can be improved but that stability and even sensitivity benefit from this approach.