The aim of this study is to explain effects of the ageing on the electrical properties of Cu/n-GaAs Shottky barrier diode with Copper Sulphide (CuS) interfacial layer. CuS thin films are deposited on n-type GaAs substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) method at room temperature. The structural and the morphological properties of the films have been carried out by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) techniques. The XRD analysis of as-grown films showed the single-phase covellite, with hexagonal crystal structure built around two preferred orientations corresponding to (102) and (108) atomic planes. The ageing effects on the electrical properties of Cu/CuS/n-GaAs/In structure have been investigated. The current-voltage (I-V) measurements at room temperature have been carried out to study the change in electrical characteristics of the devices as a function of ageing time. The main electrical parameters, such as ideality factor (n), barrier height (Phi(b)), series resistance (R-s), leakage current (I-0), and interface states (N-ss) for this structure have been calculated. The results show that the main electrical parameters of device remained virtually unchanged. (C) 2016 Elsevier Ltd. All rights reserved.