Photoelectric, stoichiometric and structural properties of n-ZnO film on p-Si

n-ZnO/p-Si heterojunction photodiodes have been fabricated by sputter deposition of n-ZnO films on p-Si substrates. Substrate temperatures of 300, 400, 500 and 600 degreesC were used for the n-ZnO film deposition using various Ar/O-2 ratios from 1:1 to 6:1. All the diodes, except for one obtained at a high substrate temperature of 600 degreesC, show strong rectifying behavior as characterized by current-voltage (I-V) measurement in a dark room. Photoelectric effects from the diodes have been observed under illumination using monochromatic red light with a wavelength of 670 nn. High levels of photocurrent or responsivity were obtained under reverse bias conditions when the stoichiometry of n-ZnO films was improved by optimizing the process conditions, such as the substrate temperature and Ar/O-2 ratio. The n-ZnO/p-Si structure prepared at 300 degreesC was found to be unsuitable because photoelectric effects were not apparent from this structure. A heterojunction diode with n-ZnO deposited at 600 degreesC was also found to be unsuitable because the dark leakage current was too high, even though the diode showed photoelectric effects. (C) 2001 Elsevier Science B.V All rights reserved.