Gas Sensors Based on Pseudohexagonal Phase of Gallium Oxide

The electrical conductivity of pseudohexagonal ε(κ)‐Ga 2 O 3 films under different ambient gases (H 2 , NO 2 , O 2 , and CO) is studied in a range of temperatures from 400 to 550 °C. The exposure of ε(κ)‐Ga 2 O 3 to reducing gases such as H 2 and CO results in a reversible increase in current and conductance. The exposure to the oxidizing gases such as NO 2 and O 2 has the opposite effect. The maximum response to reducing gases (H 2 and CO) is observed at 500 °C and to oxidizing gases at 550 and 450 °C for NO 2 and O 2 , respectively. The highest sensitivity to H 2 is achieved at low applied voltages (≤7.9 V). In contrast, the highest sensitivity to NO 2 is observed at high applied voltages. The response and recovery times and temporal drift of ε(κ)‐Ga 2 O 3 characteristics under different ambient are estimated. Polycrystalline ε(κ)‐Ga 2 O 3 exhibits the semiconducting mechanism of electron transport at high temperatures. A qualitative model of the gas‐sensing effect based on the modulation of electron concentration near the surface region of ε(κ)‐Ga 2 O 3 due to the chemisorption of gas molecules is described. Tin doping of ε(κ)‐Ga 2 O 3 increases the response to H 2 at the temperature range from 25 to 550 °C.