This paper represents the electrical and optical characteristics of a SiNW/ZnO heterojunction diode and subsequent studies on the photodetection properties of the diode in the ultraviolet(UV) wavelength region. In this work, silicon nanowire arrays were prepared on p-type(100)-oriented Si substrate by an electroless metal deposition and etching method with the help of ultrasonication. After that, catalyst-free deposition of zinc oxide(ZnO)nanowires on a silicon nanowire(SiNW) array substrate was done by utilizing a simple and cost-effective thermal evaporation technique without using a buffer layer. The SEM and XRD techniques are used to show the quality of the as-grown ZnO nanowire film. The junction properties of the diode are evaluated by measuring current–voltage and capacitance–voltage characteristics. The diode has a well-defined rectifying behavior with a rectification ratio of 190 at˙2 V, turn-on voltage of 0.5 V, and barrier height is 0.727 eV at room temperature under dark conditions.The photodetection parameters of the diode are investigated in the bias voltage range of˙2 V. The diode shows responsivity of 0.8 A/Wat a bias voltage of 2 Vunder UVillumination(wavelengthD365nm). The characteristics ofthedevice indicate that it can be usedfor UVdetectionapplicationsinnano-optoelectronicand photonic devices. This paper represents the electrical and optical characteristics of a SiNW / ZnO heterojunction diode and subsequent studies on the photodetection properties of the diode in the ultraviolet (UV) wavelength region. In this work, silicon nanowire arrays were prepared on p- type (100) -oriented Si substrate by an electroless metal deposition and etching method with the help of ultrasonication. After that, catalyst-free deposition of zinc oxide (ZnO) nanowires on a silicon nanowire (SiNW) array substrate was done by utilizing a simple and cost- The SEM and XRD techniques are used to show the quality of the as-grown ZnO nanowire film. The junction properties of the diode are evaluated by measuring current-voltage and capacitance-voltage characteristics. The diode has a well-defined rectifying behavior with a rectification ratio of 190 at˙2 V, turn-on voltage of 0.5 V, and barrier height is 0.727 eV at room temperature under da rk conditions. The photodetection parameters of the diode are investigated in the bias voltage range of˙2 V. The diode shows responsivity of 0.8 A / Wat a bias voltage of 2 Vunder UV luminescence (wavelength D365 nm). The characteristics of thedevice_device_detail that it can be usedfor UVdetectionapplicationsinnano-optoelectronicand photonic devices.