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Ultraviolet (UV) photodetectors have gained vast technological interest over the past few years due to its wide band of applications in the emerging areas of intersatellite communications, astronomical studies, and biological applications. The present challenge in UV-detector development is to improve its photosensitivity, selectivity and response time with low power consumption, which create motivation to design and fabricate the self-powered heterojunctions devices. In this work, ntype Er-doped ZnO nanowires are grown on p-type Si to make a heterojunction device by using double-step chemical bath deposition (CBD) process. The crystalline nature, morphology, optical parameters are studied in detail by using SEM, XRD, CL and UV-Vis, respectively. The XRD results confirm the growth of vertical nanowires with (002) dominant planes and such peak shifts with the increasing Er-doping, which indicates the structural modifications and strain generation due to the substitutions of Er in ZnO lattice. The optical bandgaps of the Er-doped and undoped ZnO nanowires are estimated from UV-Vis absorbance, and corresponding change in optical properties with increasing doping concentrations are studied in detail. Room temperature CL spectra confirms the reduction of oxygen vacancy related surface defects in the nanowires with increasing Er doping concentrations due to the higher bond-dissociation energy between Er-O than Zn-O. The electrical properties of the undoped and Er-doped ZnO nanowires/Si heterojunctions are investigated by measuring I-V and such results exhibit superior heterojunction properties in terms of rectification ratio, ideality factor and barrier height. Finally, selective Er-doped ZnO nanowires heterojunction shows best self-powered photoresponse under relatively low power UV illumination and such improvement in responsivity, photo-to-dark current ratio and response speed of heterojunctions is attributed to the reduction of oxygen vacancy related defects due to Er-incorporation. Therefore, current work provides an insight into the development of self-powered UV detectors by employing a cost-effective doing technique.
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