Research On Individual Quadrilateral ZnO:Ga Microwire Based Wavelength-tunable Electroluminescent Devices

Zinc oxide（ZnO）,as a semiconducting material,has attracted significant attention due to its uniqueproperties such as a wide and direct band gap（3.37 e V）and large exciton binding energy（60 me V）,and several other manufacturing advantages of ZnO,including its low cost,high stability and great tolerance to high energy radiation.It has been demonstrated that ZnO crystals have broad applications in electronic and optoelectronic,such as solid state lighting,optical interconnects,and high-density information storage.Although the research of ZnO micro/nanowire based photovoltaic devices has made great progress,the direct band gap semiconductor of III-V compounds is still difficult to integrate with silicon based system,and the fabrication of micro/nanowire based wavelength tunable light-emitting devices is slow.Electroluminescent devices based on the Joule thermal effect provide ideas for integration on silicon system to a certain extent.However,too far by demanding exacting terms,such as high-temperature thermal radiation（～3000 K）,high-vacuum encapsulation technology,restricted spectrally controllable source and so on,has greatly limited electroluminescent devices based on the Joule thermal effect application in lighting,diagnosis and treatment,communication,imaging,etc.In this paper,individual Ga-doped ZnO microwires（ZnO:Ga MWs）were successfully synthesized,which can be utilized to construct one-dimensional electroluminescent devices.The main work and some results are as follows:1.Preparation and growth mechanism of quadrilateral ZnO:Ga MWs.To prepare ZnO:Ga MWs,high-purity powders of ZnO,Ga₂O₃ and C served as the source materials.By adjusting the weight ratio of Ga₂O₃ in the precursor mixture,individual ZnO:Ga MW with with controlled Ga-doping concentration can be prepared by using chemical vapor deposition（CVD）method.The characterization of Electron Microscope and X-Ray Diffractometer reveals that ZnO:Ga MWs have smooth surface,perfect quadrilateral cross section and high crystallization quality.The length of the individual ZnO:Ga MW is～2cm and the diameter is 5-30μm.2.Individual ZnO:Ga MW based wavelength-tunable electroluminescent devices.Indium（In）particles served as the electrodes was fixed onto both ends of the wire,leading to the fabrication of single MW based metal-semiconductor-metal（MSM）structure.By adjusting the Ga-incorporation,lighting can be tuned from green-lighting,yellow-lighting,to red-lighting,with the dominant wavelengths tuned from 500 nm to 620 nm.3.Individual metal nanoparticles/ZnO:Ga MW based wavelength-tunable electroluminescent devices.Individual ZnO:Ga MW coated with metal nanoparticles decoration were fabricated by magnetron sputtering and chemical spin-coating method.Because of the coupling interaction between the surface plasmon resonance of metal nanoparticles and electroluminescence of individual ZnO:Ga MW,metal plasmons inducing the generation of hot electrons can lead to the state-filling effect in the energy-level configuration of ZnO:Ga,which can be employed to modulate the dominant emission wavelengths and regions.Based on the above observation,aligned array-type emitters and dual-color emitters with red and green emission could be realized.Individual ZnO:Ga MW based electroluminescent emitters have bright and wavelength-tunable light emission,which be integrated into chips and will pave the way towards the realization of flexible,and transparent displays,and ZnO-based on-chip optical communications.