Semimetal contacts to monolayer semiconductor: weak metalization as an effective mechanism to Schottky barrier lowering

Recent experiment has uncovered semimetal bismuth (Bi) as an excellent electrical contact to monolayer MoS$_2$ with ultralow resistance. The physics of the broader semimetal/monolayer-semiconductor family beyond Bi/MoS$_2$, however, remains largely unexplored thus far. Here we perform a comprehensive first-principle density functional theory investigation on properties between six archetypal two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors, i.e. MoS$_2$, WS$_2$, MoSe$_2$, WSe$_2$, MoTe$_2$ and WTe$_2$, two representative types semimetals, Bi antimony (Sb). As Sb work functions energetically aligns well TMDC conduction band edge, Ohmic or nearly-Ohmic $n$-type contacts are prevalent. interlayer distance semimetal/TMDC significantly larger than that metal/TMDC counterparts, which results in only weak metalization upon formation. Intriguingly, such generates semimetal-induced gap states (MIGS) extends below minimum, offering effective mechanism reduce eliminate Schottky barrier height (SBH) while still preserving electronic structures 2D TMDC. A modified Schottky-Mott rule takes into account SMIGS, interface dipole potential, Fermi level shifting is proposed, provides improved agreement DFT-simulated SBH. We further show tunneling-specific resistivity Sb/TMDC generally lower indicating better charge injection efficiency can be achieved through contacts. Our findings reveal promising potential companion electrode materials for advancing semiconductor device technology.