Study Of Piezotronics And Piezo-phototronics Effect In N-ZnO Based Pn Junction

Zinc oxide(ZnO),with a wide direct band gap of 3.37eV and a large binding energy of 60 meV,is an important II-VI semiconductor material,and is widely applicated in light emitting diode,photodetector,solar cell,pressure sensor and so on.Particularly,the unique coupled the piezoelectric,semiconducting and optical characteristics of ZnO have been forming a new field of piezotronic and piezo-phototronic effect,which has been considered as an effective approach to modulate the charge carrier generation,separation,transport and recombination at heterojunction/interface to enhance the performance of electronic devices.Piezotronic and piezo-phototronic effect have been used in lots of electronic devices,such as nanogenerator,pressure sensor and so on.However,compared with the relatively simple schottky junction,for the pn junction,the piezotronic and piezo-phototronic effect is more complex and has larger application range.So,it is important to study the piezotronic and piezo-phototronic effect of the pn junction.In this paper,we fabricated some electronic devices based on n-ZnO to study the influence of band structure,geometric parameters,and doping concentration for the piezotronic and piezo-phototronic effect.The main research contents and results are as follows:(1)The low-frequency flexible piezoelectric nanogenerators based on ZnO nanorods grown on Cu wires were fabricated by room temperature radio frequency magnetron sputtering and hydrothermal method.(2)The NiO-ZnO piezoelectric nanogenerator was fabricated by thermal oxidation and room temperature radio frequency magnetron sputtering.We have observed 21-fold higher output voltages and 13-fold higher output currents,by comparison to the devices with ZnO alone.(3)The ultrathin NiO film is deposited on ZnO nanorods as the barrier layer.The piezotronic pressure sensor based on ZnO/NiO core/shell nanorods array was fabricated by a simple and low-cost method.The switch ratio and sensitivity of the pressure sensor were optimized and significantly enhanced by the piezo-phototronic effect.(4)The UV photodetector based on ZnO/NiO pn junction was fabricated by thermal oxidation and hydrothermal method.The Ilight and sensitivity of the UV photodetector is enhanced about 74%and 78.7%,respectively by the piezo-phototronic effect.And we study the influence of the geometric parameters for the piezotronic and piezo-phototronic effect.(5)The self-power Si/ZnO heterojunction ultraviolet and visible photodetectors(PDs)with different doping concentrations were fabricated.The influence of the geometric parameters and band structure for the piezotronic and piezo-phototronic effect was studied.(6)The self-powered and broadband photodetectors based on Si/ZnO/CdO three-component heterojunctions were fabricated.The CdO film was used as the transparent electrode.And the influence of the piezotronic and piezo-phototronic effect for built-in field of pn junction was studied by Poisson's equation.