Effect of (Ce, Al) co-doped ZnO thin films on the Schottky diode properties fabricated using the sol-gel spin coating

Abstract

In this work, Schottky diodes based on undoped and (Ce, Al) co-doped ZnO thin films have been fabricated using the sol-gel spin coating. The effect of (Ce, Al) co-doped ZnO films on the structural and optical properties has been studied, and the electrical characteristic of the fabricated Schottky diode devices are investigated. X-ray diffraction and field emission scanning electron microscopy are used to study the crystalline structure and surface morphology, respectively. Room temperature Raman spectroscopy showed that the intensity of the dominant E2 high peak decreased after doping. The photoluminescence studies at room temperature showed that the intensity of the UV and the visible emission peak decreased after doping. UV-vis spectroscopy measurements at room temperature showed a decrease in the optical band gap after doping compared to undoped ZnO thin films. The I–V characteristics of fabricated Schottky diodes manifest good device behaviour at higher levels of doping (7.0 at.%) with an ideality factor of 2.40, the barrier height of 0.77 eV and series resistance of 262 Ω. The maximum rectification ratio was found to be nearly 105 at 7.0 at.%. Moreover, the electrical properties of the Schottky diode devices analyzed with Cheung-Cheung function revealed that the Schottky diode parameters were higher compared to those obtained from the conventional thermionic emission theory. Furthermore, the free electron carrier concentration for the doped samples was found to be lower compared with undoped ZnO films.