Dipole-induced transitions from Schottky to Ohmic contact at Janus MoSiGeN4/metal interfaces

Janus MoSiGeN4 monolayers exhibit exceptional mechanical stability and high electron mobility, which make them a promising channel candidate for field-effect transistors (FETs). However, the high Schottky barrier at the contact interface would limit the carrier injection efficiency and degrade device performance. Herein, using density functional theory calculations and machine learning methods, we investigated the interfacial properties of the Janus MoSiGeN4 monolayer and metal electrode contacts. The results demonstrated that the n-type/p-type Schottky and n-type Ohmic contacts can be realized in metal/MoSiGeN4 by changing the built-in electric dipole orientation of MoSiGeN4. Specifically, the contact type of Cu/MoSiGeN4 (Au/MoSiGeN4) transfers from an n-type Schottky (p-type Schottky) contact to an n-type Ohmic (n-type Schottky) contact when the contact side of MoSiGeN4 switches from Si-N to Ge-N. In addition, the Fermi level pinning (FLP) effect of metal/MoSiGeN4 with the Si-N side is weaker than that of metal/MoSiGeN4 with the Ge-N side due to the effect of intrinsic dipole and interface dipole. Notably, a simplified mathematical expression Delta V/WM is developed to describe the Schottky barrier height at metal/MoSiGeN4 interfaces using the machine learning method. These findings offer valuable guidance for the design and development of high-performance Janus MoSiGeN4-based electronic devices.