Monolayer nodal line semimetal AgTe as gate-reconfigurable ‘cold’ Ohmic contact to 2D semiconductors MoSi2N4 and WSi2N4

Abstract

MoSi${}_2$N${}_4$ and WSi${}_2$N${}_4$ are air-stable two-dimensional (2D) semiconductors promising for next-generation electronics applications. However, the challenge of forming high-quality Ohmic contacts with these materials must be addressed before their potential can be fully unlocked. In this work, we investigate the role of AgTe, a recently synthesized topological nodal line semimetal, as a high work function ($W_{\text{M}}$) semimetallic contact for MoSi${}_2$N${}_4$ and WSi${}_2$N${}_4$ using first-principles density functional theory (DFT) simulations. Phonon dispersion and ab initio molecular dynamics simulations confirm the structural stability of AgTe/MoSi${}_2$N${}_4$ and AgTe/WSi${}_2$N${}_4$ heterostructures. The high-$W_{\text{M}}$ nature of AgTe leads to $p$-type Schottky contacts. We show that electrostatic gate-induced charge doping, which can be introduced using practically achievable gating conditions, can tune the heterostructure between $n$-type and $p$-type Ohmic contacts, thus suggesting the potential of AgTe/MoSi${}_2$N${}_4$ and AgTe/WSi${}_2$N${}_4$ as gate-reconfigurable contact useful for CMOS device applications. Notably, the presence of a ‘mini gap’ above the semimetallic bands in AgTe enables the formation of $n$-type ‘cold’ Ohmic contact which is useful for steep-slope device beyond the Boltzmann’s tyranny. These findings reveal the potential of AgTe as an electrically tunable Ohmic contacts to MoSi${}_2$N${}_4$ and WSi${}_2$N${}_4$, thus paving a way for the development of high-performance 2D semiconductor-based electronics.