The Study Of Solar-Blind Ultraviolet Detector Based On ZnMgO Nanowires Network

ZnO,a wide bandgap semiconductor material,is widely used in the firlds of UV detection and solar energy due to its unique properties.However,the band gap of ZnO(3.37 eV)is undoubtedly small for the solar-blind ultraviolet(200-280 nm)detection,and an external filter is often required to reduce other long-wave interference.In this regard,selecting suitable elements for doping is an effective way to broaden the band gap of materials.It is found that Mg-doped ZnO can tune the band gap in a large scale,which can be used to fabricate solar-blind UV detectors.At present,the research of solar-blind UV detector based on ZnMgO is mainly limited to two-dimensional film materials.Moreover,compared with the two-dimensional film materials,the one-dimensional nanowire materials exhibt many special properties,which can further enhance the photoelectric response of this device.Therefore,ZnMgO nanowires network was grown on SiO2/Si substrate by high-temperature chemical vapor deposition.For realizing the purpose of direct and efficient solar-blind UV detection,Mg element was doped into ZnO to widen the band gap.Specifically,this paper includes the following two parts:The first section studies the fabrication and photoelectric performance of wurtzite structure ZnMgO nanowires network.Using MgO as the Mg source,a lower Mg-doped wurtzite Zn0.93Mg0.07O nanowires network was fabricated,and the band gap of this material was extended to 3.35 eV.Compared with the ZnO nanowires prepared in this experiment,the band gap was broadened 0.15 eV.Moreover,it was found that the photoresponse of wurtzite Zn0.93Mg0.07O nanowires network photodetector under 365 nm light irradiation is higher than that under 254 nm.It can be concluded that the lower Mg-doped wurtzite Zn0.93Mg0.07O nanowires network can not be used to fabricating efficient solar-blind UV detector.The second section mainly focuses on the fabrication and photoelectric performance of mixed-phase ZnMgO nanowires network photodetector.Instead of MgO,using Mg2N3 as the Mg source,a higher Mg-doped mixed-phase Zno.45Mg0.55O nanowires network was prepared.The bandgap gap of this material was tuned to 4.31 eV,which has a good solar-blind detection capability.At 6 V bias,the mixed-phase Zno.45Mgo.55O nanowires network solar-blind UV detector exhibits ultra-low dark current(0.2 nA),high on-off ratio(2.85x 103),a large peak responsivity(0.48 A/W)and a high external quantum efficiency(234.2%)under 254 nm irradiation.This excellent performance is comparable to other ZnMgO thin film UV photodetectors.Moreover,the detection mechanism of this photodetector was carefully analyzed.It is found that nanojunctions among Zno.45Mgo.55O nanowires and heterojunction interfaces between wurtzite and cubic structured ZnMgO in mixed-phase Zno.45Mgo.55O could be responsible for a low dark current and high responsivity of this device.