ELECTRICAL AND OPTICAL EFFECTS OF Ag DOPANT ON ZnO THIN FILM BASED MSM UV PHOTODETECTORS

Abstract

This paper presents the fabrication, characterization and performance analysis of Zinc Oxide (ZnO) and Sliver doped Zinc Oxide (SZO) based interdigitated Metal–Semiconductor–Metal (MSM) Schottky barrier UV photodetectors. The ZnO and SZO thin films were grown on p-type silicon (Si) (100) substrates by sol-gel and spin coating technique. The three devices were fabricated using silver (Ag) as Schottky contact photodetectors based on un-doped ZnO, SZO with (2% and 4%) doping ratios. The structural and morphological properties of ZnO and SZO thin films were studied using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and Atomic Force Microscopy (AFM). The optical and electrical properties for these films were studied using UV-visible and Hall effect measurements. With the applied voltage in the range of (-5 to 5 V) under dark condition, the values of the saturation current, barrier height, ideality factor, reach through and flat band voltages were extracted. Under UV illumination with different optical power levels ranging from (163.2µw -171.8µw) with a wavelength (254 nm), the values of the photo current, contrast ratio, responsivity, quantum efficiency, detectivity, and noise equivalent power were extracted. The SEM images showed a non-uniform distribution of the Ag dopants, these dopants were formed clusters and this clusters increased as the amount of Ag dopants increased. The mobility, carrier concentration, and roughness for the SZO films were increased as compared with undoped film. The optical band gap and the transmittance were decreased with increasing in the doping ratio.