In this study, Al/p-Si (MS) type photodiodes with (%2 ZnO-doped CuO) interlayer were fabricated to investigate the effects of this interlayer on the electrical characteristics. Besides, the structural properties of this interlayer were also investigated using AFM. The forward and reverse bias current voltage (I-V) measurements were carried out both in dark and various illumination intensities (10-100 mW cm(-2)) whereas the capacitance/conductance-voltage (C/G-V) measurements were carried out at various frequencies (10 kHz-1 MHz) in dark at room temperature. Experimental results show that the values of current increase with increasing illumination intensity especially in the reverse bias region due to high electric field. Furthermore, the observed good response to the illumination indicated that the fabricated structures can be used as a photo-detector/diode in the electric and optic applications. The slope (m) was obtained from the log(I-PH)-log(P) plot as 0.821 which is lower than unity which suggested that the photoconduction mechanism exhibited a linear behavior. The observed increase in the C and G values with decreasing frequency was attributed to the existence of surface states (N-ss) which are located between interlayer and semiconductor and their relaxation times. The obtained frequency dependent R-s values show that it is more effective both on the C-V and G/w-V characteristics especially at accumulation region at high frequencies.