Influence of N-vacancy on the electronic and optical properties of bulk GaN from first-principles investigations

Gallium nitride (GaN) is a promising semiconductor material for the application of the high power electronic, optoelectronic, laser diodes, etc. The previous works have been focused on the electronic and optical properties of the monolayer GaN. However, the structural, electronic and optical properties of the bulk GaN are unclear. In particular, the role of N-vacancy on the electronic and optical properties of the bulk GaN is unknown. In this work, we apply first-principles calculations to study the influence of N-vacancy on the structural, electronic and optical properties of the bulk GaN. Three bulk GaN: hexagonal (P63/mc), cubic (F-43m) and cubic (Fm-3m) are considered. The result shows that the N-vacancy is thermodynamic stability in bulk GaN. The thermodynamic stability of the GaN with the N-vacancy is demonstrated by the change of Ga-N bond. Three GaN show the semiconductor feature because of the role of N-2p state. The calculated band gap of GaN with the P63mc, F-43m and Fm-3m is 1.651, 1.489 and 0.450 eV. However, the N-vacancy enhances the electronic jump of GaN because the N-vacancy induces the move of the position of Fermi level to the region of the conduction band. The metallic behavior of GaN with the N-vacancy is demonstrated by the dielectric function diagram. In particular, the N-vacancy gives rise to the visible light region optical adsorption compared to the corresponding bulk GaN.