M3C2(OH)2 (M = Zr and Hf): An Ideal Electrode Material for sub-5 nm 2D Field-Effect Transistors

Realizing Ohmic contact is essential but challenging in the development of high-performance 2D-material-based electronics. Here, using first-principles calculations, the interfacial properties between 2D metallic M3C2T2 (M = Ti, Zr, Hf; T = O, F, OH) and 2D semiconductors are comprehensively investigated, taking group Iota V monochalcogenides in blue-phosphorene phase as example, and the performance of short-channel field-effect transistors (FETs) with M3C2(OH)(2) electrode is studied. The band alignments and the interface dipole analysis demonstrate that the M3C2(OH)(2) and Ti3C2O2 electrodes form van der Waals interaction with the group Iota V monochalcogenides, conductive to weakening the Fermi level pinning and forming desired Ohmic contacts. Moreover, owing to the large work function of the Ti3C2O2, it realizes p-type Ohmic contacts with 2D semiconductors. In addition, due to the favorable Ohmic contacts, the on/off ratio of the 5 nm gate-length Zr3C2(OH)(2)-GeTe FET is around 10(5). Moreover, for the 3 nm gate-length Zr3C2(OH)(2)-SnTe FET after adopting optimizing strategies, the on/off ratio increases from 10(2) to 10(6), and the subthreshold slope decreases from 125 mV dec(-1) to 58 mV dec(-1) below the thermionic limit (60 mV dec(-1)). The results provide a theoretical guidance for achieving the intrinsic n-type and p-type Ohmic contacts and high-performance FETs in 2D nanoelectronics.