Low-resistance ohmic contacts for NbGeN₃ enabled by cold metals

Employing cold metals with an energy gap near the Fermi level is an effective strategy to reduce contact resistance in two-dimensional devices and overcome the Boltzmann limit. Herein, using density functional theory calculations, we systematically evaluate the interfacial contact properties between monolayer NbGeN₃ and four candidate cold metals, namely NbSi₂N₄, ReSe₂, Sc(OH)₂, and Na₃ Bi. The results show that in the vertical direction, due to the Fermi level pinning effect induced by metal-semiconductor interactions, all four heterostructures form stable n-type Ohmic contacts that are largely insensitive to variations in interlayer distance, facilitating low-resistance carrier injection. In the lateral direction, ReSe₂/NbGeN₃, Na₃Bi/NbGeN₃, and Sc(OH)₂/NbGeN₃ exhibit p-type Ohmic contacts, whereas NbSi₂N₄/NbGeN₃ presents an n-type Schottky barrier of 0.32 eV. These findings reveal the potential of combining NbGeN₃ with cold metals for applications in low-power and high-performance electronic devices.