Comparative study of the micro-mechanism of charge redistribution at metal-semiconductor and semimetal-semiconductor interfaces: Pt(Ni)-MoS2 and Bi-MoS2(WSe2) as the prototype

Abstract

The generation of Schottky barrier height (SBH) at the metal–semiconductor junctions (MSJ)is a hot topic in the area of new two-dimensional (2D) semiconductors. As the charge distribution theory is an effective approach to study the generation of SBHs at the interface, and it has not been studied in depth so far. In this paper, two groups of metal–semiconductor (Pt-MoS2 and Ni-MoS2) and semimetal-semiconductor (Bi-MoS2 and Bi-WSe2) structures are designed, and their charge redistribution mechanisms are studied by the first-principles density functional theory (DFT). The result shows that the band gaps at the interfaces of Pt-MoS2 and Ni-MoS2 are 0.73 eV and 0.68 eV, respectively, and a large SBH is appeared, while the band gaps at the interface of Bi-MoS2 and Bi-WSe2 are basically not exist. The large SBHs are produced at metal–semiconductor (M−S) interfaces due to the push-back effect and metal-induced gap states (MIGS). The weak orbitals and special density of states (DOS) (near-zero DOS at the Fermi level) of Bi atoms at the semimetal-semiconductor (S-S) interface can avoid orbital hybridization and fill the band gap, thus an Ohmic Contact is formed. Additionally, stress modulation is also performed for both sets of interfaces, and the comparison shows that M−S interface is more sensitive to stress modulation than the S-S interface, and the stress has the most pronounced effect on the interface dipole (ΔV), especially at the M−S interfaces. These calculations provide a theoretical complement to the mechanism of ultra-low contact resistance formation at MSJ, bringing new theory and insight into the development of two-dimensional semiconductor devices.