Performance Analysis of n-ZnO/p-Si Heterojunction Diode as Function of Zinc Oxide Thin Films Thickness

Abstract

The n-type Zinc oxide (n-ZnO) nanostructured thin films (TFs) with different thicknesses (211, 325, 433 and 552 nm) were grown onto glass substrates employing the CVD technique at atmospheric pressure. Deposited films were characterized by EDX spectroscopy attached with FE-SEM and XRD techniques to determine the influence of thickness on elemental compositions and crystalline structure of ZnO films, respectively. Also, ZnO TFs were deposited on the p-Si(111) substrates to form different structures of n-ZnO/p-Si heterojunction diodes and then I-V characteristics were studied in the dark. The electrical parameters of the diodes such as rectification ratio (RR), reverse saturation current (Is), ideality factor (), barrier height (b) and series resistance (Rs) were calculated from the I-V measurements. EDX spectra showed that these films were only made from Zn and O elements. XRD patterns presented that the ZnO films possess hexagonal wurtzite structure with preferred orientation along [002] direction. I-V characteristics of the heterojunction diodes revealed rectification behavior and depend on ZnO TFs thickness. Also, electrical parameters of diodes were affected by the prepared film's thickness. It was found that the crystalline structure of the films and electrical properties of diodes were improved with increasing the thickness of ZnO films. It is noted that the best heterojunction diodes were that prepared with thickness (552 nm), where possess lowest value of ideality factor (3.38) and a series resistance (0.84 k) with a highest rectification ratio (1517), compared with other structures. This study offers a simple model for fabricating diodes from semiconductor films.