High performance room temperature GaN-nanowires hydrogen gas sensor fabricated by chemical vapor deposition (CVD) technique

• GaN nanowires were grown via CVD technique, show high sensitivity of 255% at RT to 1000 ppm of H2 gas.
• The sensor shows capability to detect ultra-low concentration down to 7 ppm with a sensitivity of 15% at RT.
• The high surface/volume ratio was significant parameter for the high sensing performances.

Large-scale synthesis of GaN nanowires was grown on c-sapphire substrate by chemical vapor deposition technique. X-ray diffraction, field emission scanning electron microscopy, μ-Raman and μ-photoluminescence analyses reveal that GaN nanowires crystallize within a hexagonal wurtzite-type structure with a considerably high yield, high aspect ratio of GaN NWs having an average diameter and length of 80 nm and up to several microns, respectively. A metal–semiconductor–metal (MSM) gas sensor using GaN nanowires was fabricated and hydrogen (H2)-sensing performances were examined over broad range of concentrations (7–1000 ppm) and at various operating temperatures (25,100, 150 °C). The NWs demonstrated high sensitivity up to 255% upon exposure to 1000 ppm of H2 gas at room temperature at a low power consumption of 60 μW. Additionally, at room temperature, the sensor exhibited a significant sensitivity of 83% when exposed to a very low H2 gas concentration of 34 ppm then becomes 15% at ultra low level of 7 ppm. The sensing measurements of NWs based sensor for H2 gas in the temperatures range of 25–150 °C were repeatable and reversible over a period of time of 50 min. The sensor exhibited free hysteresis phenomena after exposed to various H2 concentrations at various temperatures. The high performance of the fabricated sensor was attributed mainly to the large surface-to-volume ratio as well as the high crystallinity of the synthesized GaN NWs.