Formation of Ohmic and Schottky contacts at metal/bilayer 2D SiC interfaces by suppressing metallization of monolayer contacts: A first-principles study

Two-dimensional (2D) graphene-like silicon carbide (SiC) is a potential candidate for channel materials in next-generation optoelectronic and electronic devices. The fabrication of high-quality metal contacts (Ohmic or Schottky) is critical to the development of 2D SiC-based devices. However, the interfacial properties and the underlying mechanisms of metal/2D SiC contacts remain inadequately explored. In this paper, the interfacial properties between traditional metals (including Ag, Al, Ni, Pt, and Ti) and monolayer (ML), as well as bilayer (BL) 2D SiC, are systematically investigated via density-functional theory calculations. It is revealed that the band structures of 2D SiC exhibit strong hybridization in metal/ML 2D SiC contacts. When metals interact with ML 2D SiC, metallization occurs, potentially due to metal-induced gap states (MIGS). The band structures can be restored for metal/BL SiC contacts. Consequently, p-type Schottky contacts are formed for the Ag, Al, and Ti/BL SiC systems, while p-type Ohmic contacts are established for the Ni and Pt/BL SiC configurations. A weak Fermi level pinning with a degree of 0.79 is achieved, which may be attributed to the weak interface interaction and the suppression of MIGS.