Electrolyte Effect on Photoetching of Gallium Nitride

The limited material removal rate of conventional chemical mechanical polishing(CMP)significantly hinders the fabrica-tion efficiency and surface quality,thereby preventing the development of gallium nitride(GaN)-based devices.Moreover,the incorporation of photoelectrochemistry in CMP has garnered increasing attention because of its potential to enhance the quality and efficiency of the GaN process.However,a considerable gap still exists in the comprehensive understanding of the specific photoelectrochemical(PEC)behavior of GaN.Here,we report the influence of the electrolyte on the PEC etching of GaN.Various acids and bases were tested,with their pH being carefully adjusted.The concentrations of the cations and anions were also examined.The results showed that photocorrosion/photoetching was more pronounced in sulfuric acid,phosphoric acid,and nitric acid environments than in alkaline environments,but it was less pronounced in hydrochloric acid.Furthermore,the effects of pH and anion concentration on photoetching were investigated,and the results revealed that pho-toetching in acidic environments weakened with increasing pH levels and diminished with increasing sulfate concentration.The underlying reasons contributing to this observation were explored.These findings provide ideas for improving the pho-toetching efficiency of GaN,thereby enriching the photoelectrochemical mechanical polishing(PECMP)technology of GaN.

Formation of multifaceted nano-groove structure on rutile TiO_(2) photoanode for efficient electron-hole separation and water splitting

Photoelectrochemical(PEC)water-splitting using solar energy holds great promise for the renewable energy future,and a key challenge in the development of industry viable PEC devices is the unavailability of high-efficient photoanodes.Herein,we designed a TiO_(2) model photocatalyst with nano-groove pattern and different surface orientation using low-energy Ar+irradiation and photoetching of TiO_(2),and significantly improved the intrinsic activity for PEC water oxidation.High-resolution transmission electron microscopy directly manifests that the grooves consist of highly stepped surface with<110>steps and well-crystallized.Transient absorption spectroscopy reveals the groove surface that allows for increased recovery lifetime,which ensures promoted electron-hole separation efficiency.Surface photovoltage directly shows the carrier separation and transportation behaviors,verified by selective photodeposition,demonstrating the groove surface on TiO_(2) contributes to electron-hole separation.This work proposes an efficient and scalable photoanode strategy,which potentially can open new opportunities for achieving efficient PEC water oxidation performance.