Contact optimisation strategy for wafer-scale field-effect transistors based on two-dimensional semiconductors

Abstract

• Wafer-scale multilayered MoS2 films were fabricated by vacuum transferring technique. • A novel electrical contact architecture was proposed to improve the contact capability between 3D metal and 2D semiconductors. • A novel edge-treatment method for the MoS2 side was developed by employing a mature magnetron sputtering system. • Approximately 16 times lower contact resistivity (22.8 kΩ μm) and 3 times lower Schottky barrier height (34.6 meV) than that of the conventional top contacted devices were achieved. • Simplified resistor network model and energy-band diagrams were elaborately illustrated to discuss the mechanisms. Two-dimensional (2D) semiconductors can be utilized to continually miniaturize nanoscale electronic devices. However, achieving a practical solution for satisfying electrical contact with 2D semiconductors remains challenging. In this study, we developed a novel contact structure with transferred multilayer (t-ML) MoS 2 by integrating both edge and top contact. After in-situ plasma treatment for the edge of the MoS 2 channel and successive metal deposition, we achieved 16 times lower contact resistivity (22.8 kΩ µm) than that of the top contacted devices. The thickness-dependent electrical measurement indicates that edge contact is highly effective with thick MoS 2 due to the alleviated current-crowding effect resulting from the small contact area. The temperature-dependent transport measurement further confirms the effective minimization of the influence from the Schottky barrier and tunnelling barrier. Finally, the simplified resistor network model and energy-band diagram were proposed to understand the carrier transport mechanism. Our work provides a practical strategy for achieving excellent electrical contact between bulk metals and 2D semiconductors, paving the way for future large-scale 2D electronic devices.