Mechanism of oxygen sensing on β‐Ga 2 O 3 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 °C. For the present study, the sensors were prepared based on a β‐Ga 2 O 3 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 β‐Ga 2 O 3 single crystal depended on the operating temperature. A maximum sensitivity of ∼2.0 was obtained at temperature around 800 °C, while the shortest response time of about 5 s was found at 700 °C. Moreover, analyzing the oxygen gas‐sensing mechanism at various temperatures it can be concluded that at lower temperatures (<800 °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.