Sensing mechanisms of high temperature silicon carbide field-effect devices

Metal-insulator-silicon carbide devices have been used for gas sensing in automotive exhausts, because the large band gap of SiC allows high temperature operation up to 1200 K in chemically reactive environments. The sensor response to hydrogen containing species is due to two mechanisms whose effects are difficult to distinguish: the chemical modification of the barrier height at the metal-insulator interface and the creation/passivation of charged states at the insulator-silicon carbide interface. We describe an experimental technique combining in-situ photoemission and in-situ capacitance-voltage spectroscopy to separate the contribution of each phenomenon. Our experiment elucidates the sensing mechanism of high temperature SiC based gas sensors.