Tunable electrical contacts in two-dimensional silicon field-effect transistors: The significance of surface engineering

Abstract

Two-dimensional silicon (2D-Si) semiconductor is highly desired for future field-effect transistors (FETs) due to the inherent compatibility with the silicon-based technology. Interfacial contact represents a significant bottleneck restricting the performance of 2D-Si-based FETs. Here, by first-principles calculations and quantum transport simulations, we propose a strategy of surface engineering by F-, H-, and OH-passivation to tune the electronic properties, electrical contacts, and device performance of 2D FETs based on monolayer dumbbell silicene (LHD-Si). It is found that surface passivation performed in the LHD-Si FETs can significantly eliminate the metal-induced gap states and greatly relieve the Fermi level pinning by improving the pinning factor from 0.08 to 0.46. Importantly, the LHD-Si monolayers passivated with F and OH prefer to form n-type and p-type contacts with the representative metals (Bi, Al, Ag, Cu, Au, and Pt), respectively. Among them, Ohmic or quasi-Ohmic contacts (with very small Schottky barrier) are realized for F-passivated (OH-passivated) LHD-Si with Bi/Al/Ag (Cu/Au/Pt) electrodes. In the particular case of LHD-Si FETs with Cu electrodes, n-type, p-type, and ambipolar-type transfer behaviors are obtained for the F-, OH–, and H-passivation, respectively, demonstrating the dominant role played by electrical contacts in determining the Schottky barrier of the devices. This work highlights the significance of surface engineering in tuning the electrical contact and transport properties of doping-free 2D-Si-based FETs.