Atomically Controlled Tunable Doping in High-Performance WSe2Devices

2D transitional metal dichalcogenide (TMD) field-effect transistors are promising candidates for future electronic applications, owing to their potential for ultimate device scaling. However, it is acknowledged that substantial contact resistance associated with the contact-TMD interface has impeded device performance to a large extent. It has been discovered that O(2)plasma treatment can convert WSe(2)into WO(3-)(x)and substantially improve contact resistances of p-type WSe(2)devices by strong doping induced thinner depletion width. In this paper, temperature dependence of this conversion is studied, demonstrating an oxidation process with a precise monolayer control at room temperature and multilayer conversion at elevated temperatures. Furthermore, lateral oxidation of WSe(2)underneath contact revealed by high-resolution scanning transmission electron microscope leads to potential unpinning of the metal Fermi level and Schottky barrier lowering, resulting in lower contact resistances. The p-doping effect is attributed to the high electron affinity of the WO(3-)(x)layer on top of the remaining WSe(2)channel, and the doping level is dependent on the WO(3-)(x)thickness that is controlled by the temperature. Comprehensive materials and electrical characterizations are presented, with a low contact resistance of approximate to 528 omega mu m and record high on-state current of 320 mu A mu m(-1)at -1 V bias being reported.