Ohmic carrier transport at the edge-contacted 2D MoS₂ field effect transistors

Vertically stacked transistors using two-dimensional (2D) materials are emerging, for which a technique to precisely etch the vertically stacked 2D layered structures needs to be developed. In particular, the development of edge-contacted devices fabricated by plasma etching of the stacked structure where a metal is deposited is very important. When a metal and a 2D semiconducting material are brought into contact, Schottky barrier is formed at the interface, resulting in suppression of electronic carrier transport. However, when the metal is brought into contact with the edge of the 2D semiconducting material, an improvement in carrier transport can be expected due to the absence of the Schottky barrier. In this research, we fabricate edge-contacted field effect transistors (FETs) by bringing metal into contact with the edge of 2D molybdenum disulfide (MoS₂). We find that these FET devices exhibit Schottky contact behavior in the temperature range of 73 to 413 K but exhibit ohmic contact behavior in higher temperatures (above 433 K). Also, the ohmic behavior is observed depending on the metals used; ohmic contact is realized when metals having a high work function (palladium or gold) or semi-metals (bismuth or antimony) are brought into contact with MoS₂.