Asymmetric van der Waals Contacts Enabling High Rectification and Enhanced Optoelectronic Performance in MoS₂ Transistors

Two-dimensional MoS₂ holds great promise for next-generation electronics and optoelectronics. However, its performance is often limited by Fermi-level pinning (FLP) at metal–semiconductor interfaces. In this work, we fabricate MoS₂ transistors with asymmetric van der Waals (vdW) contacts and systematically compare three distinct electrode pair configurations (Au–Ag, Pt–Ag, and Au–Pt) using a transfer-based approach. Electrical measurements reveal that FLP is significantly suppressed, allowing the metal work function to dominate the Schottky barrier formation. Among the three configurations, the Pt–MoS_2–Ag device exhibits the highest rectification ratio of (~10^4), outperforming Au–MoS_2–Ag (~10³⁾ and Au–MoS_2–Pt (~10) by one and three orders of magnitude, respectively. This optimal performance is directly attributed to the largest work function difference within the electrode pair (ΔΦPt-Ag ≈ 1.4 eV), coupled with the effective FLP suppression by the vdW integration. Moreover, the dominant carrier type (n- or p-type) can be modulated by electrode selection. Under 532 nm illumination, the Pt–MoS_2–Ag device shows strong photoresponse with a photocurrent increase of three orders of magnitude, demonstrating its potential for self-driven photodetection.