Characterization of films and interfaces in n-ZnO/p-Si photodiodes

We report on the fabrication of n-ZnO/p-Si heterojunction photodiodes. RF sputtering was performed to deposit ZnO films on p-Si substrates at various substrate temperatures of 300, 480 and 550 °C using Ar:O2 ratios of 6:1. Typical rectifying behaviors were observed from most of the diodes as characterized by the current–voltage (I–V) measurement. Some of the diodes exhibit photoelectric effects under illumination using monochromatic red light with a wavelength of 670 nm. Maximum quantum efficiency of 53% was obtained under a reverse bias condition from a diode with ZnO film deposited at 480 °C. Measuring photoluminescence, transmittance, sheet resistance from the ZnO films, and characterizing the n-ZnO/p-Si interface with X-ray photoelectron spectroscopy, it is concluded that the diodes with n-ZnO deposited at 480 °C conserve relatively a high film quality and good interface junction to exhibit the best photoelectric property.