Hydrogen influence on electrical properties of Pt-contacted <i>α</i> -Ga <sub>2</sub> O <sub>3</sub> / <i>ϵ</i> -Ga <sub>2</sub> O <sub>3</sub> structures grown on patterned sapphire substrates
А. V. Аlmaev, В. И. Николаев, S. I. Stepanov, А. И. Печников, A. V. Chikiryaka, Nikita N. Yakovlev, V. M. Kalygina, V. V. Kopyev, Е. В. Черников
Abstract
Abstract Here we report on the influence of various gases on electrical properties of Pt-contacted α -Ga 2 O 3 and α -Ga 2 O 3 / ϵ -Ga 2 O 3 structures produced by halide vapor phase epitaxy on planar and patterned sapphire substrates. Pt-contacted α -Ga 2 O 3 structures were highly resistive and exhibited no sensitivity to H 2 and other gases. In contrast, α -Ga 2 O 3 / ϵ -Ga 2 O 3 structures grown under the same conditions on patterned sapphire substrates exhibited clear and reversible response to H 2 . The response to H 2 was thoroughly investigated at temperatures ranging from 25 °C to 200 °C and at applied biases from 1.5 V to 150 V. The lowest detectable limit of H 2 at 125 °C was found to be 54 ppm. Selectivity of Ga 2 O 3 structures against O 2 , NH 3 , СО, СН 4 , and H 2 O was examined at 125 °C and 200 °C. The structures showed little or no sensitivity to other gases at bias voltages below 7.5 V. Electrical and hydrogen sensing properties of these structures can be explained by a model of two back-to-back connected Schottky diodes which is widely used to describe metal-semiconductor-metal structures. Catalytically active Pt electrodes play an essential role in hydrogen sensing mechanism as they promote dissociation of hydrogen molecules. Accumulation of hydrogen atoms at Pt/ ϵ -Ga 2 O 3 interface results in the reduction of the Schottky energy barrier and current increase.