Probing Interface Separation for Fermi-Level Depinning in 2D Semiconductor-Metal Contacts

In recent studies of metal-semiconductor (2D) contacts, parasitic contact resistance remains problematic [1]. Fermi-level pinning is a major contributor to this issue. Various strategies have been explored to mitigate this problem, such as incorporating dielectric or semi-metallic layers at the interface to isolate the semiconductor layer and prevent the penetration of metal-induced gap states (MIGS) into the bandgap. However, the characterization of these methods in terms of interface distance is yet to be explored. Our study investigates the impact of interface separation on contact properties, including Schottky barrier heights (SBH), tunnel barrier heights (TBH), and MIGS. We aim to find the optimal separation to eliminate the MIGS effect and de-pin the Fermi level. We assess various metals (Ag, Au, Pt) when interfaced with the 2D semiconductor WS₂, exploring the potential of inducing SBH polarity based on work functions. Additionally, we present a simple first-principles approach for calculating band bending in semiconductor-metal contacts. Our study underscores the crucial role of interface separation in achieving Fermi-level depinning, which is essential for enhancing the performance of metal-semiconductor interfaces.

References:

[1]. Ghaffar, A., Ganeriwala, M. D., Hongo, K., Maezono, R., & Mohapatra, N. R. (2021). Insights into the Mechanical and Electrical Properties of a Metal–Phosphorene Interface: An Ab Initio Study with a Wide Range of Metals. ACS omega, 6(11), 7795-7803.