AlGaN/GaN heterojunction hydrogen sensor using ZnO-nanoparticles/Pd dual catalyst layer

ZnO-nanoparticles (NPs) were investigated for improving the response characteristics of a Pd-functionalized AlGaN/GaN heterojunction-based hydrogen gas sensor. The ZnO-NPs of diameter similar to 10 nm were dispersed in a co-solvent of chloroform/ethanol (chloroform 75 %, v/v), which was found to be an optimal solution for uniform dispersion, and spin coated on the surface of the fabricated Pd/AlGaN/GaN hydrogen sensor. The ZnO-NP synthesis and dispersion methods were optimized carefully before being applied to sensor fabrication. It was observed that the addition of ZnO-NPs to the Pd catalyst enhanced the hydrogen absorption so that the response of the hydrogen sensor was improved. Compared with the single Pd catalyst layer, the ZnO-NPs/Pd double layer exhibited superior response characteristics-a response of similar to 210 % and response time of similar to 2 s were achieved at 200 degrees C with a bias voltage of 3 V.