Single-Elemental Seamless Metal–Semiconductor Junctions Based on 2D Bi or Sb: Carrier Transport and Ultrafast Dynamics Study

Two-dimensional (2D) metal-semiconductor (MS) junctions with their atomically thin nature are crucial for nanoelectronics. However, van der Waals (vdW) junctions face interfacial tunneling barriers, and lateral junctions suffer from chemical bonding disorders, both limiting carrier transport. Herein, based on the layer-dependent semiconductor-to-semimetal transition in 2D bismuthene (Bi) and antimonene (Sb), lateral seamless MS junctions with native chemical bonds are constructed to inhibit tunneling barriers and produce high-quality interfaces. These coherent junctions exhibit superior transport properties, yielding a significant current response at moderate bias as continuous covalent bonding removes vdW gaps and defects. In optoelectronic applications, the photogenerated carrier lifetimes in Bi and Sb reach 61.62 and 286.16 ns owing to weak electron-phonon coupling. Furthermore, the transport and optoelectronic properties of these MS junctions exhibit superior environmental resistance, while O₂-induced trap states in Sb enhance photoconductive gain. This work provides a theoretical foundation for designing high-performance electronic and optoelectronic devices.