Unveiling the electronic properties of BiP$_3$ triphosphide from bulk to graphene-based heterostructure by first-principles calculations

Triphosphides, with a chemical formula of XP$_3$ (X is a group IIIA, IVA, or VA element), have recently attracted much attention due to their great potential in several applications. Here, using density functional theory calculations, we describe for the first time the structural and electronic properties of the bulk bismuth triphosphide (BiP$_3$). Phonon spectra and molecular dynamics simulations confirm that the 3D crystal of BiP$_3$ is a metal thermodynamically stable with no bandgap. Unlike the bulk, the mono-, bi-, tri-, and tetra-layers of BiP$_3$ are semiconductors with a bandgap ranging from 1.4 to 0.06 eV. However, stackings with more than five layers exhibit metallic behavior equal to the bulk. The results show that quantum confinement is a powerful tool for tuning the electronic properties of BiP$_3$ triphosphide, making it suitable for technological applications. Building on this, the electronic properties of van der Waals heterostructure constructed by graphene (G) and the BiP$_3$ monolayer (m-BiP$_3$) were investigated. Our results show that the Dirac cone in graphene remains intact in this heterostructure. At the equilibrium interlayer distance, the G/m-BiP$_3$ forms an n-type contact with a Schottky barrier height of 0.5 eV. It is worth noting that the SHB in the G/m-BiP$_3$ heterostructure can be adjusted by changing the interlayer distance or applying a transverse electric field. Thus, we show that few-layers BiP$_3$ is an interesting material for realizing nanoelectronic and optoelectronic devices and is an excellent option for designing Schottky nanoelectronic devices.