Effect of seed layer thickness on optoelectronic properties of ZnO-NRs/p-Si photodiodes

In this work, the effect of seed layer thickness on the optical and electrical properties of a photodiode based on zinc oxide nanorods (ZnO-NRs)/p-Si was studied. ZnO thin films of different thicknesses were deposited on a p-type single crystalline silicon substrate by the spin-coating method, and then well-aligned ZnO-NRs were grown on a seed layer by the hydrothermal method. The seed layer thickness increment enhanced the NR lengths and improved their crystallinity. Longer NRs showed lower reflectance and band gap measurements were carried out using the reflectance spectrum. The current-voltage (I-V) measurements were performed under dark and UV illumination to study the photo-detection properties of the ZnO-NRs/p-Si photodiode with different seed layer thicknesses. The diode ideality factor, barrier height, saturation current and series, and shunt resistance were determined by the dark current-voltage measurements. The dark current-voltage characteristics demonstrated an excellent rectifying behavior, and the seed layer thickness increment decreased the diode ideality factor. It was shown that the current-voltage characteristics of the fabricated devices with different seed thicknesses under UV light illumination had good sensitivities.