DEVELOPMENT OF SiC DEVICES FOR DIAGNOSTICS AND CONTROL OF COMBUSTION PRODUCTS IN ENERGY PLANT ENVIRONMENTS

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen containing species in chemically reactive, high temperature environments. The response of these metal/insulator/SiC (MISiC) devices to reducing gases has been assumed to be due to the reduction in the metal work function at the metal/oxide interface that shifts the capacitance to lower voltages. From in-situ capacitance-voltage measurements taken under sensor operating conditions we have discovered that two independent mechanisms are responsible for the sensor response to hydrogen and oxygen. We present a model of the device response based on the chemically induced shift of the metal/semiconductor barrier height as well as the passivation and creation of charged states at the SiO{sub 2}/SiC interface. The latter mechanism is much slower than the barrier height shift. Preliminary photoemission experiments have been performed to independently monitor the contribution of the two phenomena. We discuss in detail the effect of these results on sensor design and the choice of operating point for high temperature operation