High-performance methanol sensor based on GaN nanostructures grown on silicon nanoporous pillar array

GaN/Si nanoheterostructures were prepared by depositing GaN nanograins on silicon nanoporous pillar array (Si-NPA) with chemical vapor deposition method. Structural characterization elucidated that the GaN films composed of massive GaN nanocone-strings/nanowires coating on Si-NPA uniformly. Sensor device with ITO/GaN/Si-NPA/sc-Si structures was further constructed by depositing ITO interdigital electrode. Under the optimum temperature of 350 °C, the GaN/Si-NPA gas sensor demonstrated good sensing responses (R_a/R_g) of 1.22 and 1.92–5 ppm, 200 ppm methanol, respectively. The response and recovery rates to 500 ppm methanol were 8s and 7s, respectively. Such good sensing performances originated from the specific structure feature of GaN/Si-NPA nanostructure sensor, high specific surface area and large surface active sites. Moreover, the sensing mechanisms of the resulting GaN/Si-NPA nanostructure sensor were studied by drawing the methanol adsorption and desorption models based on the n-GaN/p-Si heterojunction. Our results obtained here showed that GaN/Si-NPA heterostructure might be a promising sensing candidate for detecting methanol.