Gas Sensors Based on Pseudohexagonal Phase of Gallium Oxide
А. V. Аlmaev, В. И. Николаев, P. N. Butenko, С. А. Степанов, Aleksei Pechnikov, Nikita N. Yakovlev, Igor Sinyugin, Sevastian Shapenkov, M. P. Scheglov
Abstract
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.