In this study, Au/MoS2/n-GaAs heterojunction is fabricated with single MoS2 layer and its structural, chemical and electrical parameters are investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and measurement of current-voltage (I-V) characteristics at room temperature. XRD and XPS analysis results confirm the formation of MoS2 layer on the n-GaAs surface. The electrical properties of the Au/MoS2/n-GaAs heterojunction are compared with those of the Au/n-GaAs Schottky junction. Interestingly, the heterojunction possesses a higher barrier height, lower leakage current and higher rectification ratio, in comparison with the Schottky junction. The shunt resistance (R-sh) and series resistance (R-s) are also assessed for both the junctions. Moreover, the ideality factor (n), barrier height (Phi(b)) and series resistance (R-s) are evaluated using Norde, Cheung's and surface potential (psi(s)-V) plots and the results are well-matched. Furthermore, the current transport mechanism is analyzed based on the forward bias I-V data. Lastly, the Poole-Frenkel emission conduction mechanism is employed to control the reverse bias I-V behavior of both Au/n-GaAs Schottky junction and Au/MoS2/n-GaAs heterojunction. The results demonstrate that the Au/MoS2/n-GaAs heterojunction fabricated using a simple technique is suitable for high-quality electronic and optoelectronic device applications. (C) 2019 Published by Elsevier Inc.