Contact Engineering of 2D Semiconductors using Ultrathin Transition Metal Dichalcogenides as a Contact Interlayer

Two-dimensional (2D) semiconductors such as transition metal dichalcogenides (TMDs) have emerged as a promising candidate for post-silicon electronics. However, a major impediment in the realization of their electronics applications is their tendency to form a substantial Schottky barrier with most commonly used metals to form electrical contacts. Various strategies to reduce this barrier are deficient as they lack thermal or chemical stability, or reduce the overall performance. Here, we present a new method to significantly reduce the barrier height at the semiconductor/metal interface by inserting ultrathin TMD as an interlayer. Particularly, we observed an order of magnitude reduction of contact resistance to 1.6 kΩ●μm and significant improvement of overall device performance in MoS₂ transistors as the Schottky barrier height is lowered from ~ 100 meV to ~ 40 meV by inserting a WSe₂ interlayer between the MoS₂ channel and the metal electrodes. A significant advantage of using 2D semiconductors as a contact interlayer as opposed to previously reported insulator interlayers is that 2D semiconductor interlayers with appropriate band alignments are able to effectively reduce the Schottky barrier height without introducing a substantial tunneling barrier at the contacts.