Study On The Preparation And The Photoelectric Properties Of ZnO Based PN Junctions

Zinc oxide?ZnO?is a direct band oxide semiconductor whose band gap is 3.37eV at room temperature.ZnO intrinsically shows n-type character because of the exsitance of defects.ZnO thin films with other forms of ZnO materials are thought as good candidates in applications such as light emission,UV detection,photocatalysis,transparent conductive oxide?TCO?,piezoelectricity and thin film triansistor?TFT?,benefiting from ZnO's high exciton binding energy,high electron saturated drift velocity and high chemical stability.This paper focuses on ZnO thin flim materials:1)A novel solution-derived method has been developed to deposite ZnO thin films.Intrinsic and Al-doped ZnO thin flims are synthesized via this method.Tests of XRD,SEM,UV-vis Spectrum and Photoluminescence are carried out respectively to study phase composition,surface topography and optical properties of the samples.The results show that samples synthesized by this method are pure and the doping of Al ionic has influence on the growth of crystal.Then cadimium sulfide?CdS?thin films are deposited by a chemical bath deposition?CBD?method and are together with ZnO layers to form an?Al?ZnO/CdS/Si p-n heterojunction structure using B doped singal crystal sillicon?Si?sheet as both p-type layer and substrate.Studies on the influence of CdS layer and Al doping are taken.The results show that the barrier height is made lower,the behavior of carrier transport is optimized and the idea factor of the heterojunction diode is optimized because of the addition of CdS buffer layer.2)Intrinsic,Al doped and In doped ZnO thin flim transistors are made by building a ZnO/SiO₂/Si structure with Si sheets which are obtained after oxidation in high temperature.Intrinsic and Al doped ZnO TFTs show a character of depletion mode and In doped ZnO TFTs show a character of enhancement mode.3)Al-N co-doping ZnO thin films are synthesized on glass substrate by sol-gel method with spin coating process.The optical porperties of the samples are studied.The results show that transmittance of samples made by the methods is bigger than 80%in the range of visible light and it reveals that the band gap width increases with the increasing amount of nitrogen?N?.4)N doped ZnO thin films with different MEA/Zn²⁺ratio?0.5,1.0,1.5,2.0?are deposited by the solution-derived method.Tests of XRD,SEM,Raman spectrum and photocurrent are carried out respectively to study phase composition,surface topography and photoelectric properties of the samples.The results show that ZnO thin film with MEA/Zn²⁺=1.5 has the best property of photoresponse?the largest rate of currents with light on and off,the least dark current and fastest response rate?.The Al:ZnO/ZnO:N p-n homojunction is build on ITO substrate and the property of UV detection of the junction is studied.The result shows that the junction has rapid response time?rising time 2ms and recovery time 22ms?and low dark current(10^-7A).5)BGZO/i-ZnO/CdS/Ag-CuInS₂/ITO structure solar cells are build using solution-derived ZnO and RF magnetron sputtering made ZnO for comparion.The results show that the former dosen't behave well and should be optimized further.