First-principles study of distance-dependent electronic coupling in TMD–metal interfaces

Parasitic contact resistance remains a major obstacle to the performance of 2D transition metal dichalcogenide (TMD)–semiconductor interfaces. A key reason for this is Fermi-level pinning (FLP), which arises from metal-induced gap states (MIGS) that extend into the semiconductor bandgap. This problem is particularly severe when using high-work-function metals such as gold (Au), palladium (Pd), and platinum (Pt). TMD contacts with these high-work-function metals make it difficult to achieve the p-type Schottky barrier height (SBH). Several strategies have been proposed to address this issue, including inserting dielectric or semimetallic layers at the interface to suppress MIGS. However, the specific role of interface separation in modifying contact properties has not been thoroughly studied. In this work, we use first-principles calculations to investigate how the distance between the metal and the semiconductor affects FLP, MIGS suppression, and key barrier properties. We focus on metal–semiconductor interfaces involving high-work-function metals (Au, Pd, Pt) and two commonly studied TMDs: WS 2 and MoS 2 . We analyze how SBH, tunnel barrier height (TBH), band bending, MIGS penetration, and the Fermi-level pinning index (S) change as the interface distance increases. Our results show that increasing the separation between the metal and semiconductor systematically reduces MIGS. This weakens FLP and allows the SBH to depend more directly on the metal’s work function. As a result, SBH polarity can be aligned with predictions from the Schottky–Mott limit, enabling the design of both n-type and p-type contacts. We also calculate band bending to understand how charge transfers across the interface. Overall, our findings provide critical insight into the role of interface separation in 2D metal–semiconductor contacts. This study can serve as a foundation for future research aimed at improving contact performance and overall device efficiency. • Trend in interface separation with MIGS, SBH, TBH and Fermi-level pinning (FLP). • FLP-free contacts achieved at 5 Å interface separation across all metals. • SBH polarity aligns with Schottky–Mott limit as separation increases. • Tunneling barrier height rises sharply beyond 4 Å, reducing transmission • Design trade-off: FLP suppression vs. carrier injection efficiency.