Theoretical prediction of electronic structures and optical properties of Y-doped γ-Si3N4

The crystal structures, electronic structures, and optical properties of Y-doped γ-Si3N4 were studied by using first-principles calculations based upon the density functional theory with Perdew-Burke-Enzerh (PBE) generalized gradient approximation (GGA). The band gap (Eg) of Y-doped γ-Si3N4 is found to significantly decrease in comparison to that of γ-Si3N4. The calculated Eg suggests that γ-Si3N4 doped with low Y content can be used in the window or absorption material of solar cell, while those doped with high Y concentrations can show metal behavior. The calculation of optical properties shows that the static dielectric constant of γ-Si3N4 doped with Y is much higher than that of the undoped γ-Si3N4, implying its special applications in electronics and optics.