The comparison of optical and photodetector properties of Zn, Al and Sn doped and undoped CdS thin films via chemical bath deposition

Abstract

We deposit undoped CdS thin films as well as doped CdS thin films with Zn, Al, and Sn via chemical bath deposition method. We then investigate the optical and photodetector properties of these two. Our results show that the particle size of CdS:Zn thin film is smaller than undoped CdS thin film. In addition, the CdS:Sn thin film shows a special morphology which is a combination of spherical and elongated particles. CdS:Sn thin film has a higher surface to volume ratio in comparison to undoped CdS thin film. We find out that the thickness of CdS:Zn, CdS:Al, CdS:Sn and undoped CdS thin film are 380, 350, 190 and 320 nm, respectively. The optical band gap of CdS:Zn, CdS:Al, CdS:Sn and undoped CdS thin film are 2.49, 2.42, 2.78, and 2.53 eV, respectively. Moeover, photosensivity of CdS:Sn thin film (Iph/Id) is (approximately) 904 at bias voltage of 10 V, which is higher than the other thin films. This phenomenon is related to lower sulfur vacancy. Finally, we propose that alloying with tin could be effective in eliminating cadmium vacancy and hence improving the detector performance.