A Universal van der Waals Tunneling Injector for Monolayer CMOS

Two-dimensional (2D) semiconductors are poised to extend logic technology to the atomic-thickness limit, yet monolayer complementary metal-oxide-semiconductor (CMOS) has been largely hampered by polarity-dependent, thermionic-emission-dominated contacts that preclude a unified injection solution. Here, we introduce degenerately doped, crystalline SnSe₂ as a universal source-side van der Waals (vdW) injector capable of enforcing all-tunneling carrier injection into both p- and n-type monolayer channels. The combination of a large electron affinity (∼5.1 eV), degenerate carrier density (>10¹⁹ cm^-3), and atomically uniform vdW interfacial coupling enables polarity-tailored tunneling mechanisms while effectively suppressing interfacial gap states. In p-type WSe₂, a type-III (broken gap) alignment drives efficient band-to-band tunneling, yielding a >1000-fold enhancement in drive current over conventional metal electrodes. In n-type MoS₂, the SnSe₂ injector forms a type-I heterojunction within the sub-depletion-width monolayer body, enabling a gate-tunable injection that evolves from field-controlled Fowler-Nordheim-like tunneling to thickness-limited tunneling, achieving an on/off ratio > 10⁹ and a subthreshold swing below 70 mV dec^-1. Integrating this single-material injector, we demonstrate a monolayer CMOS inverter with a maximum voltage gain of ∼340 at V_DD = 2 V, establishing degenerate SnSe₂ as a dual-polarity vdW injector and providing a platform for high-performance, low-power 2D integrated circuits.