High-k Monolayer CaF₂ as the Gate Dielectric for Two-Dimensional SiC-Based Field-Effect Transistors

Exploring gate insulators suitable for two-dimensional (2D) semiconductors that can be extended to the nanometer range is of great importance for the development of nanoelectronics. In this paper, the structural and electrical properties of a high- k CaF 2 monolayer serving as the gate dielectric for 2D SiC-based field-effect transistors are systematically investigated using first-principles calculations. It is found that a stable van der Waals (vdW) contact can be formed between CaF 2 and 2D SiC. In addition, ab initio molecular dynamics simulations show that the interface structure of 2D SiC/CaF 2 possesses high thermal stability. Compared with the available vdW gate dielectric hexagonal boron nitride (hBN), CaF 2 ’s interactions with 2D SiC exhibit higher structural stability with a lower lattice mismatch rate and a stronger binding energy. In addition, the valence band offset of 2D SiC/CaF 2 is as high as 3.5 eV, which could overcome the unacceptable gate leakage current for hBN serving as the gate dielectric. It is further found that the dielectric properties of CaF 2 are not deteriorated by carbon antisite and interstitial defects on the 2D SiC surface.