Production and characterization of NİO: ZNO / CDO composite photodiodes by sol-jel method

In this study, NiO:CdO and NiO:ZnO thin films with different molar ratios were formed on p-Si with aluminum (Al) ohmic contacts. Sol-gel spin coating method was used as coating method and coating process was performed in dynamic mode. Al top contacts were formed on thin films by thermal evaporation method using a physical mask. After all these processes, Al/NiO:CdO/p-Si/Al and Al/NiO:ZnO/p-Si/Al composite based photodiodes were produced. X-ray diffraction (XRD) analysis was performed to determine the phases forming the produced thin films. The morphologies of the structures forming the thin films were investigated by field emission scanning electron microscopy (FE-SEM) at different magnifications. The elements that compose the thin films were determined by energy dispersive X-ray spectroscopy (EDX). Photodiode parameters of produced photodiodes were investigated by current-voltage (I–V), capacitance-voltage (C-V), conductivity-voltage (G-V), transient photocurrent-time (I–t) and transient photocapacitance-time (C–t) measurements. I-V analyzes were performed in the dark and under different light intensities (20 - 100 mW/cm^2), and I–t analyzes were performed only at light intensities varying between 20 - 100 mW/cm^2. C-V, G-V and C-t measurements were performed at different frequency values (10 kHz - 1 MHz). NiO:CdO and NiO:ZnO thin films were produced successfully and it was seen that all thin films were composed of nanostructures. It was determined that Al/NiO:CdO/p-Si/Al and Al/NiO:ZnO/p-Si/Al composite based photodiodes showed rectification behavior. Photocurrent values were affected by light and it was determined that they increased as the light intensity increased. It was determined that all produced photodiodes were sensitive to light. The highest photoresponse value was obtained as 3.12 x 10^3 in Al/NiO:ZnO/p-Si/Al composite based photodiode, which NiO:ZnO ratio of 3:1. It has been seen that the electrical and photoresponse properties of the produced photodiodes can be changed and controlled by the NiO:CdO-ZnO ratios. It was determined that the series resistance and interface state densities of Al/NiO:CdO/p-Si/Al and Al/NiO:ZnO/p-Si/Al composite based photodiodes were affected by frequency and NiO:CdO-ZnO ratio. As a result of all the characterizations, it was concluded that the produced devices can be used as photocapacitors and photodiodes in optoelectronic systems.