First-principles study electronic and optical properties of p-type Al-doped γ-Si3N4

The energetics, electronic structure, and optical properties of Al-doped γ-Si3N4 with different concentration are studied based on density function theory within the generalized gradient approximation (GGA). The binding energy and the formation energy suggest that Al impurities prefer to substitute Si at octahedral sites. Different doping concentrations are considered and the corresponding density of states (DOS) analyzed. Calculated DOS indicates that there are holes in the top of the valance band after doping, meaning a p-type doping. We study the complex dielectric function, the absorption coefficient, and the electron energy loss spectra. It is demonstrated that for the low Al concentration, the material exhibits the dielectric behavior and for the high Al concentration, the material is possible to exhibit the metallic behavior. The γ-Si3N4 doped with Al has a much higher static dielectric constant than undoped γ-Si3N4, implying its potential applications in electronics and optics.