Research On The AlGaN-based Photoelectrochemical Self-Powered Ultraviolet Photodetectors

Ultraviolet detection has attracted extremely intensive attention because of its great potential applications in civil and military fields,such as ozone monitoring,water quality detection,and missile warning.Conventional solid-state ultraviolet photodetectors（UV PDs）have many problems,such as high consumption,complex preparation process,and high cost,which greatly limit their production.Compared with conventional UV PDs,the photoelectrochemical UV PDs（PEC UV PDs）have the advantages of high photoresponse,simple manufacturing process,low cost,and environment-friendly,which have potential application prospects in complex and harsh environments,and have become a research hotspot.In recent years,some semiconductors with wide bandgaps,such as TiO₂,ZnO,SnO₂,Ga₂O₃,GaN,and other materials,have been widely used in ultraviolet detection,among which AlGaN-based nanostructures have good photosensitivity in the UV region,which are suitable for the preparation of UV PDs.In particular,AlGaN/GaN nanowires（NWs）heterojunctions have been paid close attention in the field of photoelectrochemical detection due to their unique transport properties.However,the enhanced photoresponse performance of dual-spectral and solar-blind PEC UV PDs based on the p-AlGaN/n-GaN NWs and the transport mechanism of carriers in the detection process remains to be further investigated.To solve the above problems,the self-powered PEC UV PDs based on p-AlGaN/n-GaN NWs with large-to-volume ratio and high crystalline quality are studied in the paper,and the device performances are improved by optimizing materials,surface modification,and structure design.The main research contents and achievements of this paper are as follows:（1）The phenomenon of polarity reversal of the photocurrent under different optical excitation wavelengths is realized by designing the p-AlGaN/n-GaN NWs with different n-GaN NWs thicknesses,which indicates that the GaN link layer has a strong regulatory effect on the transport of photogenerated carriers,thus achieving dual-spectral PEC UV PDs.（2）It is found that Pt nanoparticles can effectively promote the generation,separation,and transport of photogenerated carriers,and the quantum dot decoration and the increase of Mg doping temperature can further enhance the device performance by studying the effects of platinum（Pt）nanoparticles modification,quantum dot decoration,and the temperature of Mg doping.（3）The super-sensitive solar-blind UV PD can be realized by using the AlN insertion layer into the p-AlGaN/n-GaN nanowire structure,which benefits from that the AlN insertion layer can optimize the properties of p-AlGaN nanowire and accelerate the transport and separation of photogenerated electron-hole pairs,resulting in more photogenerated electrons gathering on the surface of p-AlGaN nanowires to participate in the hydrogen evolution reduction reaction.（4）The photoresponse of the solar-blind UV PD is further improved by introducing a heavily doped tunneling junction in the p-AlGaN/n-GaN nanowire structure combined with Pt modification.The ultra-high responsivity of 102.54 m A W^-1 and the fast response time of 15 ms are achieved at the255 nm illumination,which reveals that the p⁺⁺-GaN/n⁺⁺-GaN NWs tunneling junction plays a crucial role in promoting carriers transport and reducing the photogenerated carriers recombination within the AlGaN NWs.In this paper,the research on the p-AlGaN/n-GaN NWs-based PEC UV PDs provides an important theoretical basis and feasible design scheme for further exploration of low-cost,multifunctional,high-performance photodetectors,sensors,PEC cells,and other optoelectronic devices.