Physical and electronic properties of ZnO:Al/porous silicon

UV, violet and blue-green photoluminescence has been achieved at room temperature (RT) from ZnO:Al (AZO) films deposited by radio frequency (rf) co-sputtering. As the ZnO target power increases from 100 W, the violet luminescence vanishes and the blue and green-blue luminescences appear. The most intense UV and blue-green luminescence is obtained for the films deposited at higher sputtering powers depending upon the stoichiometry of the films as well as the crystalline quality. The as-prepared porous silicon (PS) emission band lies in the blue-green spectral region and is blue shifted due to the AZO deposition. The current-voltage characteristics of AZO/PS heterostructures have been studied. The ideality factor is found to be 19 and the series resistance as determined from the forward characteristics is 36 MΩ