Group III-nitride-based gas sensors for combustion monitoring

The paper reports on novel gas-sensing devices based on group III-nitride materials. Both platinum (Pt)-GaN Schottky diodes as well as high-electron-mobility transistors formed from GaN/AlGaN heterostructures with catalytically active platinum gates were investigated. The performance of these devices towards a number of relevant exhaust gas components such as H₂, HC, CO, NO_x was tested. Test gas concentrations were chosen to simulate exhaust gas emissions from lean-burn 4-stroke petrol engines. We found that GaN-based devices with platinum electrodes are mainly sensitive to hydrogen and unsaturated hydrocarbons with a sizeable cross-sensitivity to CO and NO₂. These performance characteristics are similar to those of comparable SiC devices. With GaN devices this performance, however, can be obtained at a reduced complexity of the device processing and a greater freedom in the choice of sensor architectures.