Structural, morphological, optical, and gas sensing characteristics of ultraviolet-assisted photoelectrochemical etching derived AlInGaN nano-spikes

Abstract

The formation of nano-dendritic like structure and nano-spikes in AlInGaN films via ultraviolet-assisted photoelectrochemical (PEC) etching at different current densities (5, 20, and 40 mA/cm2) could be potentially deployed as the hydrogen sensor. The ability of nano-dendritic like structure and nano-spikes to provide large surface area to volume ratio could improve hydrogen (H) adsorption in the AlInGaN films, and thereby offering a greater sensitivity as compared to the as-grown film. The film subjected to PEC etching at 40 mA/cm2 has demonstrated the highest sensitivity (79.6%), followed by that subjected to PEC etching at 20 and 5 mA/cm2. The acquisition of the highest sensitivity in the aforementioned film suggested that nano-spikes (40 mA/cm2) surpassed nano-dendritic like structures (5 and 20 mA/cm2) in term of providing larger surface area to volume ratio for H adsorption. Moreover, the largest total dislocation density present in the nano-spikes film could be the reason contributing to the increased gas sensitivity because the dislocation could serve as the trapping sites to mediate the diffusion of the adsorbed H, and thus facilitating the H detection. As a result, a fast response time (105 s) and recovery time (46 s) was obtained. Keywords: AlInGaN, Photoelectrochemical, Nano-spikes, Dislocation, Sensitivity, Response