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

摘要

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 (H_2)-sensing performances were examined over broad range of concentrations (7-1000 ppm) and at various operating temperatures (25,100, 150 ℃). The NWs demonstrated high sensitivity up to 255% upon exposure to 1000 ppm of H_2 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 H_2 gas concentration of 34 ppm then becomes 15% at ultra low level of 7 ppm. The sensing measurements of NWs based sensor for H_2 gas in the temperatures range of 25 -150 ℃ were repeatable and reversible over a period of time of 50 min. The sensor exhibited free hysteresis phenomena after exposed to various H_2 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.