Zero-dipole Schottky contact: Homologous metal contact to 2D semiconductor

Band alignment of metal contacts to 2D semiconductors often deviates from the ideal Schottky–Mott (SM) rule due to non-idealities such as the formations of interface dipoles and metal-induced gap states (MIGS). Although MIGS can be suppressed using van der Waals (vdW) contacts, the interface dipole is hard to eliminate due to the electronegativity difference of the two contacting materials. Here, we show that interface dipoles can be nearly eliminated in 2D semiconducting MoSi2N4 when contacted by its homologous metallic counterpart MoSi2N4(MoN)n (n = 1–4). The SiN outer sublayers, simultaneously present in both MoSi2N4 and MoSi2N4(MoN)n, create a near-equal charge “push-back” effect at the contact interface. The nearly symmetrical charge redistribution without net electron transfer across the interface results in a zero-dipole contact. Notably, we show that even in the extreme close-contact case where MoSi2N4(MoN) is arbitrarily pushed toward MoSi2N4 with an extremely small interlayer distance, the interface dipole remains practically zero. Such a zero-dipole Schottky contact represents a peculiar case where the SM rule, usually expected to occur only in the non-interacting regime, can manifest in MoSi2N4/MoSi2N4(MoN)n vdWHs even when the constituent monolayers interact strongly. We show that MoSi2N4/MoSi2N4(MoN) forms a quasi-Ohmic contact with an ultralow Schottky barrier and the electrical injection current varies nearly linearly with the metal/semiconductor interlayer distance, thus providing a potential platform for nanoelectronics and mechano-electrical pressure sensing applications. These findings reveal a route to achieve zero-dipole contacts to 2D semiconductors using homologous metals for electronics and optoelectronics device applications.