High-Performance WSe₂ Top-Gate Devices with Strong Spacer Doping

Because of the lack of contact and spacer doping techniques for two-dimensional (2D) transistors, most high-performance 2D devices have been produced with nontypical structures that contain electrical gating in the contact regions. In the present study, we used chloroauric acid (HAuCl₄) as a strong p-dopant for WSe₂ monolayers used in transistors. The HAuCl₄-doped devices exhibited a record-low contact resistance of 0.7 kΩ·μm under a doping concentration of 1.76 × 10¹³ cm^-2. In addition, an extrinsic carrier diffusion phenomenon was discovered in the HAuCl₄-WSe₂ system. With a suitably designed spacer length for doping, a normally off, high-performance underlap top-gate device can be produced without the application of additional gating in the contact and spacer regions.