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Study Of Metal Localized Surface Plasmon-decorated ZnO Heterostructure Ultraviolet Light-emitting Devices

Posted on:2015-10-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:C ZhangFull Text:PDF
GTID:1228330467961327Subject:Condensed matter physics
Abstract/Summary:PDF Full Text Request
ZnO, as wide band-gap semiconductor material (3.37eV), has high exciton bindingenergy of60meV, easy to obtain excitonic emission at high temperature, and is regarded asthe ideal candidate for the development of ultraviolet (UV) light-emitting devices. At present,it has become the research focus of the third generation semiconductor materials after GaN.Under the status of a huge challenge in p-type doped ZnO, building ZnO-based heterojunctionlight-emitting device may well be an ideal strategy. Improvement and enhancement ofefficiency in ZnO-based light-emitting devices have been the unremitting pursuit of the goal.Metal localized surface plasmon, with high spatial localization property and strong local-fieldenhancement property, in recent years, is considered to be an effective means to enhanceefficiency of light-emitting devices. In this thesis, based on the preparation of ZnO-basedmetal-insulator-semiconductor (MIS) heterostructure and PIN heterostructure light-emittingdiode (LED), we introduce Ag nanoparticles localized surface plasmon (LSP) to construct aAg LSP enhanced ZnO-based prototype LED; Using resonant coupling effect between AgLSP and ZnO excitons, the internal quantum efficiency and light extraction efficiency of thedevice was improved; We systematically discussed the effect including the property of AgLSP and device structure on ZnO-based LED; For the structural characteristics of differentdevices, some physical mechanisms of the intrinsic luminescence enhancement were revealed.The specific content is as follows:Ag LSP-enhanced ZnO UV LED device based on Au/MgO/Ag/MgO/ZnO MISheterostructure was designed and prepared. In this device, MgO layer, not only acted as anelectron blocking layer and a hole injection layer, but also serve as the dielectric spacer layerin LSP/exciton coupling processes. It is revealed the influence and regulation about thicknessproportion of two layers of MgO, which affected Ag LSP-enhanced ZnO UV emission.Considering an evanescent wave of LSP, nonradiative energy transfer, charge transportprocess and other factors, we optimized the MgO layer thickness to achieve a maximum of10-fold ZnO UV electroluminescence enhancement. Time-resolved photoluminescencemeasurements showed that the increased spontaneous emission rate resulted from resonantcoupling between Ag LSP and ZnO exciton (the improvement of internal quantum efficiency).Novel structure design provides the help of fabricating the metal LSP-decorated ZnO MISheterojunction device.Ag nanoparticles LSP-enhanced n-ZnO/ZnO nanorod arrays/p-GaN heterostructure LEDwas designed and prepared, coating MgZnO layer on the surface of ZnO nanorod arrays, byoptimizing the thickness of MgZnO spacer layer, a10-fold selective emission enhancement ofZnO UV electroluminescence was achieved. The introduction of Ag LSP led to the increasedZnO spontaneous emission rate, but the enhancement mechanism can not completely attributeto the direct coupling between Ag LSP and ZnO exciton in the active region, because "distantdistance" from the Ag nanoparticles to the active layer has contradiction with regard to LSPnear-field characteristics. Theoretical simulation and experimental measurement of the spatial distribution of light-emitting intensity indicated that: ZnO/MgZnO core shell nanorod arraysserved as a medium of optical waveguide, resulting in the spread of electroluminescence inarrays. Therefore, a luminescence enhancement process including some physical modelsshould be metioned, which involves electroluminescence in heterojunction area, waveguidepropagation, self-absorption and remotivation of ZnO luminescence, and resonant couplingbetween ZnO exciton and Ag LSPs. In addition, the increased external quantum efficiency ofthe device is also due to the role in light extraction of Ag nanoparticles LSP. Based on thematching problem between the resonance frequency of Ag nanoparticle LSP and ZnO UVlight-emitting energy, attempt and outlook are taken into consideration. Ag nanowires, used oftheir greater adjustable range of LSP resonance frequency, which are instead of Agnanoparticles, are introduced into device, to be constructed the similar aforementionedstructure. A preliminary study on improved photoluminescence performance of Agnanowire-decorated ZnO/MgZnO core shell nanorod array structure was also in process. It ishelpful that we construct the electroluminescence device with this structure in the followingstudy.
Keywords/Search Tags:Ag localized surface plasmon, MIS heterojunction, PIN heterojunction, ZnO-based ultraviolet light-emitting devices, luminescence enhancement, spontaneousemission rate, internal/external quantum efficiency
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