Alleviation of Schottky barrier heights at TMDs/metal interfaces with a tunneling layer of semiconducting InSe nanoflake

Two-dimensional transition metal dichalcogenides (TMDs) are promising for post-Moore electronic applications, however, the device performance is strongly limited by the large Schottky barrier height (SBH) at TMDs/metal interfaces. Herein, by carrying out conductive atomic force microscopy (C-AFM), temperature-dependent transport measurements, and density functional theory (DFT) calculations, it is demonstrated that the insertion of a two-dimensional semiconductor InSe between metal and TMDs can effectively alleviate the SBHs with preservation of high tunneling efficiency, and enhance the device performance of both p-type WSe₂ and n-type MoS₂ transistors. Specifically, SBHs in MoS₂ and WSe₂ transistors were reduced from 156 to 33 meV and from 95 to 16 meV, respectively, giving rise to dramatically improved on-state current and carrier mobilities of the devices. This is attributed to the coupling effects from Fermi level pinning between metal and InSe, optimized hybrid electronic structure and appropriate band alignment of InSe/TMD heterostructures. Our work provides an avenue to tailor the contact engineering of TMDs devices by inserting appropriate 2D materials guided from the band alignment of the heterostructures.