GaN with Laterally Aligned Nanopores to Enhance the Water Splitting

Abstract

GaN with aligned nanopores was fabricated using a lateral anodic etching process in HNO3 solution. This laterally porous structure can be modified from triangular pores to quasi-circular pores with increasing the voltage, indicating the transformation from anisotropic etching gradually toward isotropic etching. Furthermore, we have established the correlation between the etching current and pore trajectories based on the in situ chronoamperometry and find that the lateral etching is initially driven by the avalanche effect, then enter a steady state as a balance between the oxidation and dissolution of GaN at the pore tips. The water splitting properties of the laterally porous photoanode have also been studied. Compared with the as-grown GaN film, nearly 3.4 times enhancement of self-driven photocurrent was achieved for the porous GaN with triangular pores. Our findings not only reveal the formation kinetics of porous GaN but also pave a way for the application of solar water splitting using laterally porous GaN.