Contact Doped Multi-layer Tungsten Diselenide Field Effect Transistors

According to the conventional transistor process including the silicon semiconductor device, it is the common practice to heavily dope contact regions under the metallic electrodes by using the ion implantation technique so as to minimize contact resistance. In this study, we demonstrate a contact doping technique applied to the ultra-thin (2~5 nm) tungsten diselenide (WSe₂) channel formed in field effect transistors (FET) by applying the selective oxidation process to the contact regions. Using our devices that underwent the contact doping, we were able to achieve high performance p-type FET electrical properties with an on/off ratio of 10⁸, a field effect mobility of 180 cm²/Vs and a contact resistance of 1 kΩμm. Importantly, Schottky barrier heights (SBH) and Fermi level pinning factors of the contact doped WSe₂ FET were measured by employing various work function metals (In, Ti, Au, Pd) as the electrodes. We were able to derive the relationship between the Schottky barrier heights and the contact resistances very reliably.