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 ΔV/W_M 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.