High-Performance WSe<sub>2</sub> Top-Gate Devices with Strong Spacer Doping.

Ho, Po-Hsun; Yang, Yu-Ying; Chou, Sui-An; Cheng, Ren-Hao; Pao, Po-Heng; Cheng, Chao-Ching; Radu, Iuliana; Chien, Chao-Hsin · Nano Lett · 2023

basic_science · Level V

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Abstract

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 (HAuCl<sub>4</sub>) as a strong <i>p</i>-dopant for WSe<sub>2</sub> monolayers used in transistors. The HAuCl<sub>4</sub>-doped devices exhibited a record-low contact resistance of 0.7 kΩ·μm under a doping concentration of 1.76 × 10<sup>13</sup> cm<sup>-2</sup>. In addition, an extrinsic carrier diffusion phenomenon was discovered in the HAuCl<sub>4</sub>-WSe<sub>2</sub> 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.