Investigations on Field‐Effect Transistors Based on Two‐Dimensional Materials

In the present article, experimental and theoretical investigations regarding field‐effect transistors based on two‐dimensional (2D) materials are presented. First, the properties of contacts between a metal and 2D material are discussed. To this end, metal‐to‐graphene contacts as well to transition metal dichalcogenides (TMD) are studied. Whereas metal‐graphene contacts can be tuned with an appropriate back‐gate, metal‐TMD contacts exhibit strong Fermi level pinning showing substantially limited maximum possible drive current. Next, tungsten diselenide (WSe2) field‐effect transistors are presented. Employing buried‐triple‐gate substrates allows tuning source, channel and drain by applying appropriate gate voltages so that the device can be reconfigured to work as n‐type, p‐type and as so‐called band‐to‐band tunnel field‐effect transistor on the same WSe2 flake. Two‐dimensional (2D) materials are being considered ideally suited for ultimately scaled field‐effect transistor devices due to their extremely thin thickness and excellent electronic transport properties. The realization of the appropriate contacts and doped source/drain regions is, however, difficult. Multigate substrates are being employed here, that allow generating potential landscapes within 2D field‐effect transistor devices, facilitating electronic transport studies, as well as the realization of reconfigurable device functionalities.