Investigation On Silver-nanoparticle Resonance Enhanced ZnO-based UV Photodetectors

The third-generation wide band gap?3.37 eV?semiconductor material ZnO has the advantages of environmental friendliness,low defect density and strong radiation resistance,which enable them to be an ideal candidate material for the preparation of UV photodetectors.Aiming at resolving the existed problem of the low absorption of ZnO-based UV photodetecctors,we are looking at the ultraviolet detector of metal localized surface plasma modification.Metal localized surface plasmon,with high spatial localization property and strong local-field enhancement property,in recent years,is considered to be an effective means to enhance light absorption efficiency of ZnO film.In this thesis,the photodetector was decorated by Ag nanoparticles,whose quality factors is high in the UV range.The main researches are as follows:?1?From the angle of increasing the light absorption rate standpoint,we have decorated Ag nanoparticles on the surface of the traditional MSM structure ZnO-based UV photodetector.The size and density of Ag nanoparticles were controlled by varing the sputtering time,and the optimized parameters were obtained.The results showed that when the sputtering time was 15 s,the responsivity of the device was increased from 0.20 A/W to0.33 A/W.It indicated that the resonance frequency of Ag nanoparticle LSP can match with the exciton-responsive reigon of ZnO,and the absorption of ZnO film was increased efficiently.?2?In order to increase the number of Ag nanoparticles,we embedded Ag nanoparticles with different layers in ZnO films.The results indicated that when two Ag nanoparticle layers were embedding in the ZnO film,the responsivity of detector increased8 times compared to the ZnO-based detector.Based on the Zn O/Ag/ZnO/Ag/ZnO?ZAZAZ?strcctured photodetector,starting from the effective penetration depth of the localized surface plasmon in the dielectric materials,we investigated with an emphasis on the effects of the spacing between the two Ag nanoparticle layers.When the spacing between two Ag layers was 57.13 nm,the responsivity of ZAZAZ structured detector was increased nearly10 times compared to ZnO detectors.In addition,the cutoff wavelength of the photodetector responsivity was redshifted,which could boarden the detection range.The results effectively validates the propagation characteristics of localized surface plasmon evanescent wave.?3?From the angle of improving the ability of collecting photo-generated carriers,the traditional device structure was changed,and a dual-wave UV detector with a Mg_0.24Zn_0.76O/Au/ZnO sandwich structure was prepared.The ability of collecting photo-generated carriers was improved efficiently.At the same time,Ag nanoparticles were introduced to modify the detector,and the modification position of the Ag nanoparticles were adjusted.The results demonstrated that the Mg0.24Zn0.76O/Au/Ag NPs/ZnO structured detector shows the best performance.The responsivity of the ZnO layer and the Mg0.24Zn0.76O layer were increased 3.8 times and 4.2 times in comparation with the device of the Mg_0.24Zn_0.76O/Au/ZnO structured photodetector.Basing on the Mg_0.24Zn_0.76O/Au/Ag NPs/ZnO structured detector,we embedding Ag nanopartices with different depth in the bottom Mg_0.24Zn_0.76O layer,which could realize responsiveness adjustable high performance dual-band detectors.