Towards Control of Band Gap in Two-Dimensional Hexagonal Boron Nitride by Doping

Recently boron nitride received a lot of attention due to its applications in optoelectronic devices, composites, and biological materials. In particular, it was proved to be useful as supporting substrates and gate dielectric layers in graphene-based structures. We performed first-principles calculations for aluminum doped two-dimensional (2D) hexagonal boron nitride (h-BN) layers. We found that the band gap strongly depends on Al concentration and increasing Al concentration diminishes the electronic band gap due to the formation of intermediate states in the h-BN gap. For Al concentration of 12.5%, the electronic band gap becomes 4.1 eV compared to 5.97 eV in the original undoped h-BN material. Such a significant band gap reduction makes this material promising for using in different UV optoelectronic and high-power electronic devices. We also statistically analyzed how interatomic distances between substitutional Al defects in this materials affect the value of the band gap. We found that the position of corresponding intermediate bands strongly depends on the interatomic distances between the substitutional defects. We also studied the statistical band gap distribution in doped boron nitride. In particular, we show that increasing concentration of Al substitutional defects in Al-doped h-BN increases the thermodynamic stability of the system which is also favorable for using heavily doped boron nitride in optoelectronic devices.