Mechanism of oxygen sensing on -Ga2O3 single-crystal sensors for high temperatures

The oxygen-sensing mechanism on gallium oxide sensors has been analyzed in the presence of an oxygen gas flow at elevated temperatures: 700, 750, 800, 850, 900, 950, and 1000 degrees C. For the present study, the sensors were prepared based on a -Ga2O3 single crystal in a sandwich structure using three different shapes of the electrodes: quadratic-spot, plate, and mesh type. The results revealed that the oxygen-sensor performances (sensitivity and response/recovery time) of the -Ga2O3 single crystal depended on the operating temperature. A maximum sensitivity of approximate to 2.0 was obtained at temperature around 800 degrees C, while the shortest response time of about 5s was found at 700 degrees C. Moreover, analyzing the oxygen gas-sensing mechanism at various temperatures it can be concluded that at lower temperatures (<800 degrees C) the oxygen sensitivity and the response time are drastically influenced by the surface reactions, while above this temperature a main influence of bulk processes combined with the formation of the more complex vacancy-related defects can be seen.