Tunable ohmic van der Waals-type contacts in monolayer C3N field-effect transistors.

Monolayer (ML) C3N, a novel two-dimensional flat crystalline material with a suitable bandgap and excellent carrier mobility, is a prospective channel material candidate for next-generation field-effect transistors (FETs). The contact properties of ML C3N-metal interfaces based on FETs have been comprehensively investigated with metal electrodes (graphene, Ti2C(OH/F)2, Zr2C(OH/F)2, Au, Ni, Pd, and Pt) by employing ab initio electronic structure calculations and quantum transport simulations. The contact properties of ML C3N are isotropic along the armchair and zigzag directions except for the case of Au. ML C3N establishes vertical van der Waals-type ohmic contacts with all the calculated metals except for Zr2CF2. The ML C3N-graphene, -Zr2CF2, -Ti2CF2, -Pt, -Pd, and -Ni interfaces form p-type lateral ohmic contacts, while the ML C3N-Ti2C(OH)2 and -Zr2C(OH)2 interfaces form n-type lateral ohmic contacts. The ohmic contact polarity can be regulated by changing the functional groups of the 2D MXene electrodes. These results provide theoretical insights into the characteristics of ML C3N-metal interfaces, which are important for choosing suitable electrodes and the design of ML C3N devices.

Isotropic Contact Properties in Monolayer GeAs Field-Effect Transistors.

Owing to the tunable bandgap and high thermodynamic stability, anisotropic monolayer (ML) GeAs have arisen as an attractive candidate for electronic and optoelectronic applications. The contact properties of ML GeAs with 2D metal (graphene, Ti2CF2, V2CF2, and Ti3C2O2) and Cu electrodes are explored along two principal axes in field-effect transistors (FET) by employing ab initio electronic structure calculations and quantum transport simulations. Weak van der Waals interactions are found between ML GeAs and the 2D metal electrodes with the band structure of ML GeAs kept the same, while there is a strong interaction between ML GeAs and the Cu metal electrode, resulting in the obvious hybridization of the band structure. Isotropic contact properties are seen along the two principal directions. P-type lateral Schottky contacts are established in ML GeAs FETs with Ti3C2O2, graphene, and Ti2CF2 metals, with a hole Schottky barrier height (SBH) of 0.12 (0.20), 0.15 (0.11), and 0.29 (0.21) eV along the armchair (zigzag) direction, respectively, and an n-type lateral Schottky contact is established with the Cu electrode with an electron SBH of 0.64 (0.57) eV. Surprisingly, ML GeAs forms ideal p-type Ohmic contacts with the V2CF2 electrode. The results provide a theoretical foundation for comprehending the interactions between ML GeAs and metals, as well as for designing high-performance ML GeAs FETs.