Improvement of Contact Resistance and 3D Integration of 2D Material Field-Effect Transistors Using Semi-Metallic PtSe₂ Contacts

In this work, the potential of 2D semi-metallic PtSe₂ as source/drain (S/D) contacts for 2D material field-effect-transistors (FETs) through theoretical and experimental investigations, is explored. From the density functional theory (DFT) calculations, semi-metallic PtSe₂ can inject electrons and holes into MoS₂ and WSe₂, respectively, indicating the feasibility of PtSe₂ contacts for both n- and p-metal-oxide-semiconductor FETs (n-/p-MOSFETs). Indeed, experimentally fabricated flake-level MoS₂ n-MOSFETs and WSe₂ p-MOSFETs exhibit a significant reduction in contact resistance with semi-metallic PtSe₂ contacts compared to conventional Ti/Au contacts. To demonstrate the applicability for large-area electronics, MoS₂ n-MOSFETs are fabricated with semi-metallic PtSe₂ contacts using chemical vapor deposition-grown MoS₂ and PtSe₂ films. These devices exhibit outstanding performance metrics, including high on-state current (≈10⁻⁷ A/µm) and large on/off ratio (>10⁷). Furthermore, by employing these high-performance MoS₂ n-MOSFETs, vertically stacked n-MOS inverters are successfully demonstrated, suggesting that 3D integration of 2D material FETs is possible using semi-metallic PtSe₂ contacts.