Advanced beyond-silicon electronic technology requires both channel materials and also ultralow-resistance contacts to be discovered^1,2. Atomically thin two-dimensional semiconductors have great potential for realizing high-performance electronic devices^1,3. However, owing to metal-induced gap states (MIGS)^4,5,6,7, energy barriers at the metal–semiconductor interface—which fundamentally lead to high contact resistance and poor current-delivery capability—have constrained the improvement of two-dimensional semiconductor transistors so far^2,8,9. Here we report ohmic contact between semimetallic bismuth and semiconducting monolayer transition metal dichalcogenides (TMDs) where the MIGS are sufficiently suppressed and degenerate states in the TMD are spontaneously formed in contact with bismuth. Through this approach, we achieve zero Schottky barrier height, a contact resistance of 123 ohm micrometres and an on-state current density of 1,135 microamps per micrometre on monolayer MoS₂; these two values are, to the best of our knowledge, the lowest and highest yet recorded, respectively. We also demonstrate that excellent ohmic contacts can be formed on various monolayer semiconductors, including MoS₂, WS₂ and WSe₂. Our reported contact resistances are a substantial improvement for two-dimensional semiconductors, and approach the quantum limit. This technology unveils the potential of high-performance monolayer transistors that are on par with state-of-the-art three-dimensional semiconductors, enabling further device downscaling and extending Moore’s law.

先进的超硅电子技术需要发现通道材料和超低电阻触点^1,2。原子级薄的二维半导体在实现高性能电子设备^1,3方面具有巨大潜力。然而，由于金属诱导间隙态 (MIGS) ^4,5,6,7，金属-半导体界面处的能垒——从根本上导致高接触电阻和差的电流传输能力——限制了两个-迄今为止的三维半导体晶体管^2,8,9. 在这里，我们报告了半金属铋和半导体单层过渡金属二硫属化物 (TMD) 之间的欧姆接触，其中 MIGS 被充分抑制，并且 TMD 中的简并态在与铋接触时​​自发形成。_{通过这种方法，我们在单层 MoS 2}上实现了零肖特基势垒高度、123 欧姆微米的接触电阻和每微米 1,135 微安的通态电流密度；据我们所知，这两个值分别是有记录以来的最低值和最高值。我们还证明了可以在各种单层半导体上形成出色的欧姆接触，包括 MoS ₂、WS ₂和 WSe ₂. 我们报告的接触电阻对于二维半导体来说是一个实质性的改进，并且接近了量子极限。该技术揭示了高性能单层晶体管的潜力，可与最先进的 3D 半导体相媲美，从而进一步缩小器件尺寸并扩展摩尔定律。