High temperature hydrogen gas sensing property of GaN prepared from α-GaOOH.

Highlights • Gallium Nitride (GaN) based-hydrogen gas sensor for high temperature application were prepared. • GaN powder with different oxygen impurities were synthesized from α-GaOOH by a direct nitridation method. • Oxygen presence is behind the enhanced gas sensing sensitivity of GaN. • Band energy structure and carrier concentration of GaN are affected by oxygen content. • The obtained GaN-sensor exhibited excellent sensitivity than its oxide (β-Ga 2 O 3). Abstract Extremely stable gas sensors at elevated temperature (T > 400 °C) with rapid detection of hydrogen gas are urgently demanded especially for hydrogen production industry which typically involves a high-temperature system. Gallium nitride (GaN) possesses excellent physicochemical properties and is expected to be one candidate for high temperature gas sensor. In this work, the GaN preparation from α–GaOOH precursors by a direct nitridation method under NH 3 flow is presented. The nitridation was done at various temperatures to obtain GaN with different oxygen contents, which played a vital role in gas sensing response of thick film GaN in various concentration of H 2 gas at 500 °C. The sensitivity of the obtained GaN with 2.07 wt.% of oxygen content was 10 times higher than that sample with the lowest oxygen content (1.9 wt.%) and the sensitivity drastically decreased when the oxygen content was 2.53 wt.%. The sensors also demonstrated high stability as indicated by their repeatable feature after being exposed at a various concentration of H 2 (150–750 ppm). Furthermore, the GaN showed higher sensitivity than that of β–Ga 2 O 3 sensor. [ABSTRACT FROM AUTHOR]