Ag/ZnO/p-Si/Ag heterojunction and their optoelectronic characteristics under different UV wavelength illumination

•ZnO was prepared via hydrothermal process on top of a p type Si for photodetector application.•The prepared p-n junction show a good rectifying behaviour.•It was noticed that the barrier height decreased with the UV wavelength higher than the energy band gap.•On contrary with the barrier height the ideality factor show maximum values at the same UV wavelengths. An ultraviolet (UV) photodiode was fabricated by employing zinc oxide (ZnO) nanorods (NRs) grown on a p-type silicon (Si) wafer. The fabricated heterojunction was characterised for its crystal structure, morphology, chemical state, and the photoluminescence emission. The current–voltage characteristics show that the junction exhibits good rectification characteristics, with a reverse leakage current of 1.2nA and a rectification ratio of 210 at 5V. Furthermore, the calculated barrier height and the ideality factor were 0.78eV and 2.3, respectively. The photodiode was illuminated with different UV wavelengths (300–400nm). The output measurements of the photocurrent showed the maximum range of values for the wavelength at 350–370nm. The barrier height was at its minimum value, and the ideality factor was at its maximum value in the wavelengths with energies near the energy band gap of the ZnO NRs. The results reveal the relation between the UV wavelengths, the barrier height, and the ideality factor. The fabricated photodiode reveals acceptable properties with responsivity of 0.6 A/W at wavelength 370nm and 5V reverse bias.