Contact engineering for temperature stability improvement of Bi-contacted MoS2 field effect transistors

Semimetallic bismuth (Bi) is one of the most effective strategies for reducing the contact resistance of two-dimensional transition metal dichalcogenide field effect transistors (FETs). However, the low melting point of Bi contact (271.5° C) limits its reliable applications. In this study, we demonstrated that the temperature stability of Bi-contacted electrodes could be improved by inserting a high-melting point semimetallic antimony (Sb) between the Bi contacting layer and the gold (Au) capping layer. The proposed Bi/Sb/Au contact electrodes tended to form a metal mixture with a continuous surface during the heating process (Voids appeared on the surface of the Bi/Au contact electrodes after heating at 120° C). Because of the improved contacting layer formed by the semimetal Bi/Sb alloy, the fabricated Bi/Sb/Au-contacted molybdenum sulfide (MoS2) FETs with different gate lengths demonstrated higher on-state current stability after heating treatment than the Bi/Au contact. Because of the Bi/Sb/Au contact and poly (methyl methacrylate) package, the MoS2 FETs demonstrated time stability of at least two months from the almost unchanged transfer characteristics. The electrical stability indicates that the insertion of semimetallic Sb is a promising technology for reliable Bi-based contact.