Electrical Contacts in Monolayer MoSi 2 N 4 Transistors.

The latest synthesized monolayer (ML) MoSi 2 N 4 material exhibits stability in ambient conditions, suitable bandgap, and high mobilities. Its potential as a next-generation transistor channel material has been demonstrated through quantum transport simulations. However, in practical two-dimensional (2D) material transistors, the electrical contacts formed by the channel and the electrode must be optimized, as they are crucial for determining the efficiency of carrier injection. We employed the density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) method to systematically explore the vertical and horizontal interfaces between the typical metal electrodes and the ML MoSi 2 N 4 . The DFT+NEGF method incorporates the coupling between the electrode and the channel, which is crucial for quantum transport. Among these metals, Sc and Ti form n -type Ohmic contacts with zero tunneling barriers at both vertical and horizontal interfaces with ML MoSi 2 N 4 , making them optimal for contact metals. In-ML MoSi 2 N 4 contacts display zero Schottky barriers but a 3.11 eV tunneling barrier. Cu and Au establish n -type Schottky contacts, while Pt forms a p -type contact. The Fermi pinning factors of the metal-ML MoSi 2 N 4 contacts for both electrons and holes are above 0.51, much higher than the typical 2D semiconductors. Moreover, there is a strong positive correlation between the Fermi pinning factor and the band gap, with a Spearman rank correlation coefficient of 0.897 and a p -value below 0.001. Our work provides insight into the contact optimization for the ML MoSi 2 N 4 transistors and highlights the promising potential of ML MoSi 2 N 4 as the channel material for the next-generation FETs.