Because of the intrinsic low carrier density of monolayer two-dimensional (2D) materials, doping is crucial for the performance of underlap top-gated 2D devices. However, wet etching of a high-k (dielectric constant) dielectric layer is difficult to implement without causing performance deterioration on the devices; therefore, finding a suitable spacer doping technique for 2D devices is indispensable. In this study, we developed a remote doping (RD) method in which defective SiOx can remotely dope the underlying high-k capped 2D regions without directly contacting these materials. This method achieved a doping density as high as 1.4 × 1013 cm-2 without reducing the mobility of the doped materials; after 1 month, the doping concentration remained as high as 1.2 × 1013 cm-2. Defective SiOx can be used to dope most popular 2D transition-metal dichalcogenides. The low-k properties of SiOx render it ideal for spacer doping, which is very attractive from the perspective of circuit operation. In our experiments, MoS2 and WS2 underlap top-gate devices exhibited 10× and 200× increases in their on-currents, respectively, after being doped with SiOx. These results indicate that SiOx doping can be conducted to manufacture high-performance 2D devices.
Keywords: defective SiOx; low-k materials; remote doping; spacer doping; top-gate transistors; two-dimensional materials.