High-temperature thin-catalytic gate devices for combustion emissions control

4H- and 6H-SiC Schottky diodes responding down to 5 ppm of NO and NO2 gases at temperatures up to 450ºC were fabricated. Upon exposure to gas, the forward current of the devices changes due to variations in the Schottky barrier height. For NO gas, the response follows a simple Langmuir adsorption model. Device parameters were evaluated from linear conductance/current versus conductance plots, with improved accuracy. The linearity of these plots is an indication that the devices are not being affected by interfacial oxide layers or pinning of the Fermi level. 4H-SiC devices showed slightly superior stability and sensitivity for this application.