Light-emitting Diodes Based On Individual ZnO Microwires

Ultraviolet light sources,such as light-emitting diodes(LEDs)and laser diodes(LDs),have drawn widespread attention for their versatile potential applications,such as water and air purification,biomedical sterilization,photolithography,and so forth.Compared with toxic,bloated,and inefficient gas lasers and mercury lamps,semiconducting light sources with gaseous lasers and mercury lamps,semiconductor based light sources with a compact structure,small size,and light weight,thus have broad application in military affairs and civil areas.Wide band gap semiconductors,such as diamond,III-V nitride semiconductors(GaN,AlGaN,and AlN),and II-VI oxide semiconductors(ZnO and MgO),are potential candidates for ultraviolet optoelectronic devices.ZnO is a direct bandgap II-VI oxide semiconductors material with wide bandgap(3.37 eV).It has high chemical stability,large photoelectric coupling coefficient,high exciton binding energy(60 meV)and excellent optical and electrical properties.It has been widely used in optoelectronic devices,gas sensors,solar cells and ultraviolet detection.In addition,compared with other micro/nano structure crystals,ZnO semiconductor materials have the characteristics,such as high crystallization quality,easy preparation,abundant raw materials,safety and environmental protection,and are potential application materials for manufacturing high-efficiency and stable ultraviolet micro/nano photoelectric devices.However,ZnO semiconductor materials still some problems,such as low carrier transfer efficiency,difficult to control surface defects,metal-semiconductor contact-induced Joule heat dissipation,low light-emitting efficiency of heterojunction devices,and difficulty in tuning ultraviolet wavelength.Therefore,in order to solve the above problems,this paper focuses on the growth of controllable Ga-doped ZnO microwires,the design and fabrication of light-emitting and heterojunction ultraviolet light-emitting diode devices based on ZnO:Ga microwires,and achieves the following innovative research results:1.ZnO: Ga microwires with different Ga doping concentration were successfully grown by gas phase transfer method.With the increase of Ga doping concentration,a single ZnO microwire exhibits typical near-band-edge PL emission,with the central wavelength shifting from 390 nm to 370 nm.The results show that the band gap of ZnO can be effectively controlled by introducing Ga doping elements,and the emission wavelength of ZnO near-band-edge(NBE)PL can be tuned.2.The n-ZnO:Ga/p-GaN heterostructures were constructed by using different Ga doping concentration of ZnO microwires.The near-band-edge emission(FWHM~10 nm)of the ZnO microwires was obtained as the dominant ultraviolet emission.With the increase of Ga doping concentration,the ultraviolet wavelength of the heterostructure can be tuned,and the radiation range ranges from 384 to 372 nm.The reason can be attributed to the Moss-Bolstein effect caused by the intervention of Ga dopants,which inhibits EL emission at the interface and makes the near-band edge emission of ZnO microwires dominant.The feasibility of ZnO microwires optical bandgap engineering and its potential application value in wavelength tunable ultraviolet light source are further confirmed.3.Using the local plasmon decay of metal nanoparticles(such as Au,Ag and Al)to induce the generation of "hot electrons",we can improve the reinjection of ZnO microwires carriers,regulate the surface defects of ZnO,and then prepare a fluorescent filament light source with adjustable central wavelength in the visible band.It also provides good technical and theoretical support for the follow-up study of efficient light emitting diodes and laser diodes.