Tuning the Schottky barrier height in a multiferroic In₂Se₃/Fe₃GeTe₂ van der Waals heterojunction

The ferroelectric material In₂Se₃ is currently of significant interest due to its built-in polarisation characteristics that can significantly modulate its electronic properties. Here we employ density functional theory to determine the transport characteristics at the metal-semiconductor interface of the two-dimensional multiferroic In₂Se₃/Fe₃GeTe₂ heterojunction. We show a significant tuning of the Schottky barrier height as a result of the change in the intrinsic polarisation state of In₂Se₃: the switching in the electric polarisation of In₂Se₃ results in the switching of the nature of the Schottky barrier, from being n-type to p-type, and is accompanied by a change in the spin polarisation of the electrons. This switchable Schottky barrier structure can form an essential component in a two-dimensional field effect transistor that can be operated by switching the ferroelectric polarisation, rather than by the application of strain or electric field. The band structure and density of state calculations show that Fe₃GeTe₂ lends its magnetic and metallic characteristics to the In₂Se₃ layer, making the In₂Se₃/Fe₃GeTe₂ heterojunction a potentially viable multiferroic candidate in nanoelectronic devices like field-effect transistors. Moreover, our findings reveal a transfer of charge carriers from the In₂Se₃ layer to the Fe₃GeTe₂ layer, resulting in the formation of an in-built electric field at the metal-semiconductor interface. Our work can substantially broaden the device potential of the In₂Se₃/Fe₃GeTe₂ heterojunction in future low-energy electronic devices.