Research Of Photodetector And Its Pyroelectric Effect Based On ZnO Nanowire Heterojunctions With Different Lengths

As a wide bandgap semiconductor ideal material,zinc oxide(ZnO)exhibits good optoelectronic properties,and also has piezoelectric and pyroelectric effects due to its special non-central symmetric crystal structure,which shows unique advantages in the development and regulation of high-performance photodetectors(PDs),and thus has been one of the popular materials for researchers in optoelectronic device research.However,from past reports,there are few studies on the effect of ZnO nanowires(NWs)length on the devices,and because of its large band gap width,the wavelength response range of photodetectors is generally limited to the UV band,while studies and reports on its broadband detection are still lacking.Therefore,in this paper,based on the ZnO NWs heterojunction PDs,we systematically study the effect of the length change of ZnO NWs on the photodetector performance by changing the length of different ZnO NWs,and use its pyroelectric effect to improve the photodetection performance of the device,and also realize the self-powered function of the device with broadband response.The main research contents are as follows:(1)The p-Si/n-ZnO/ITO heterojunction PDs with lengths of 200 nm,400 nm,500 nm,700 nm,and 1000 nm ZnO NWs were grown by hydrothermal method at different hydrothermal reaction times.The basic properties of the samples were characterized by SEM,XRD,PL,absorption and transmission spectroscopy,and the effect of different lengths of ZnO NWs on the light absorption performance was investigated,and it was found that the longer the NWs,the stronger the absorption of light.The I-V test and the calculation of the optical responsivity and detectivity of the samples showed that both the responsivity and detectivity of the samples decreased with the increase of laser power,but strongly depended on the length of the ZnO NWs,and the sample of 400 nm has the best responsivity,with a responsivity reaching 0.12 A/W.The influence of the pyroelectric effect on the time response characteristics of the p-Si/n-ZnO/ITO heterojunction was also studied.The maximum R_pyro+photoof 1.74 m A/W can be obtained at an optical power intensity of 2.55 m W/cm²and there is no external field,under 450 nm laser irradiation,which is 1350%higher compared to only the photoelectric effect.(2)The ITO/ZnO/PEDOT:PSS organic/inorganic heterojunction PDs with different lengths of ZnO NWs were grown by the same ZnO NWs preparation method,and the effects of the length of ZnO NWs and the variation of laser power on the photodetection performance were investigated.The I-V curve shows that the device has good rectification characteristics.By calculating its responsivity and detection,it was found that the sample's responsivity and detection strongly dependent on the length of the NWs.When the bias voltage of 0.4 V and under 360 nm laser irradiation and at a power intensity is 2.55 m W/cm²,the sample of the length of the ZnO NWs is 200 nm has the highest responsivity and detectivity,which are107.95 A/W and 72.69×10¹⁰Jones,respectively.The time response characteristics of the ITO/ZnO/PEDOT:PSS heterojunction are also studied.The pyroelectric effect not only greatly improves the optical response performance of the device,but also realizes the self-powered function of the device with broadband response from 360 nm to 1550 nm.Under1550 nm laser irradiation,when the optical power intensity was 254.78 m W/cm²and no external field,the maximum R_pyro+photocan be obtained is 0.0067?A/W,which is about 1000%of R_photo.