MXene Interlayer for Fermi Level Pinning Mitigation in Metal/2D SiC Contacts: A First-Principles Study

Abstract

Two-dimensional (2D) silicon carbide (SiC) has emerged as a promising channel material for next-generation optoelectronic and electronic devices due to its excellent properties such as direct wide band gap and high carrier mobility. However, the practical application of 2D semiconductor in transistors is hindered by the difficulty in fabricating high-quality metal contact, primarily originated from strong Fermi-level pinning (FLP) at the metal/semiconductor interface. In this work, a novel semiconductor/MXene/metal (MMS) contact architecture is proposed to effectively alleviate the FLP at metal/2D SiC interface. The interfacial electronic properties of conventional metal contacts (Au, Ti, Mg, Ag, Li, Al, Pd, Pt, and Cu) with 2D SiC are first systematically investigated using density-functional theory (DFT) calculations. Vertical and lateral Schottky barrier heights (SBHs) were evaluated and categorized by combining band structure analysis with ab initio quantum transport simulations. The extracted FLP factor of 0.30 reveals a strong FLP in direct metal/2D SiC contacts. By inserting a Ti3C2T2 (T=OH, F, O) MXene interlayer between the metal and 2D SiC, distinct contact behaviors are achieved: n-type Ohmic contact in metal/Ti3C2(OH)2/2D SiC, p-type Schottky contact in metal/Ti3C2F2/2D SiC, and p-type Ohmic contact in metal/Ti3C2O2/2D SiC, with a weak dependence on the metal electrode types. The FLP effect is significantly alleviated, as evidenced by an increased FLP factor of 0.77. This improvement is attributed to the disruption of direct metal/2D SiC interaction and the effective suppression of metal-induced gap states (MIGS). As a result, the SBHs become tunable by engineering functional T groups of Ti3C2T2.