P-ZnO/n-Si Photodiodes Prepared by Ultrasonic Spraying Pyrolysis Method

ZnO ultraviolet (UV)/visible photodiodes were fabricated. The N-In codoped p-type ZnO films were deposited on (111)-oriented silicon substrate by ultrasonic spraying pyrolysis method. It was found the photocurrent approximately 3.9 10 A at a bias of 1 V and a photocurrent to dark current contrast ratio higher than around two orders of magnitude. The photodiodes exhibited two higher responsive regions denoted as A and B, respectively. Region A at wavelength from 400 nm to 700 nm was owing to ZnO film absorption occurring through the band-to-deep level, and region B at wavelength from 700 nm to 1000 nm was owing to Si substrate absorption occurring through the band edge.