【Epitaxy Papers】O₂ sensors for λ-probe based on β-Ga₂O₃ microcrystals fabricated from к-Ga₂O₃ epitaxial film by thermal annealing

      Researchers from the National Research Tomsk State University have published a dissertation titled "O₂ sensors for λ-probe based on β-Ga₂O₃ microcrystals fabricated from к-Ga₂O₃ epitaxial film by thermal annealing" in Sensors and Actuators B: Chemical.

Abstract

      Gas-sensitive β-Ga₂O₃ microcrystals on GaN were self-formed as a result of solid-state phase transition from an HVPE κ-Ga₂O₃ epitaxial layer with Pt contacts during its high-temperature annealing (30 min at 1000°C in air). The β-Ga₂O₃ microcrystals are characterized by increased electrical conductance and high gas response compared to the epitaxial κ-Ga₂O₃ and β-Ga₂O₃ films. The response of the β-Ga₂O₃ microcrystals to 5 vol% of O₂ was 11.33 at the temperature of maximum response corresponding to 650°C. It was shown that the gas-sensitive characteristics of the β-Ga₂O₃ microcrystals change weakly under cyclic O₂ exposure, as well as under changes in the relative humidity of the gas mixture in the range of 8–70% and depend significantly on the polarity of the applied voltage. The samples showed high sensitivity to NO and CO₂. The responses at 650°C to 1 ppm of NO and 1 vol% of CO₂ were 1.7 and 10.4, correspondingly. The mechanism of the observed effect and the possibility of using the β-Ga₂O₃ microcrystals for sensitive elements of λ-probes are discussed.

DOI：

https://doi.org/10.1016/j.snb.2025.138355