The effect of biaxial tensile strain on structure and photoelectric properties of Fe-doped GaN monolayer

Under a biaxial tensile strain of 0% to 5%, the formation energy, band structure, dielectric function, absorption coefficient, reflectivity coefficient and loss function of Fe-doped two-dimensional (2D) GaN are systematically calculated based on the density functional theory, and the mechanism of bandgap variation is analyzed in detail. It is found that the bond lengths of Fe-N and Ga-N increase linearly and the bandgap changes quadratically with the increase of biaxial tensile strain. The results demonstrate that the 2D GaN: Fe is a direct bandgap semiconductor and its bandgap type would not be affected by biaxial tensile strain. The static dielectric constant of unstrained 2D GaN: Fe is 28.6, with the increase of biaxial tensile strain, the dielectric constant of 2D GaN: Fe increases, resulting in the charge storage capacity of 2D GaN: Fe enhancing and the parasitic capacitance increasing, the peak values of the absorption coefficient, refractive index and loss function increase with increasing strain, these results indicate that the biaxial tensile strain can seriously affect the optical properties of 2D GaN: Fe.