Structural and electronic properties of point defects in Haeckelite GaN monolayer

First-principles calculations are carried out to investigate the physical properties of Haeckelite gallium nitride monolayer with point defects, including three vacancies and three antisites. Optimized geometries, band structures and magnetic properties modified by defects are demonstrated. We find that the lattice constant and cohesive energy only get slight change compared with the perfect monolayer, while the band gap and magnetic moment appear observable variations. The VN (vacancy of N atom) induces a defect state which leads the system to be metallic; The VGa (vacancy of Ga atom), VGaN (vacancy of GaN pair) and one of Ga↔N (exchanging neighboring atoms) defects introduce net magnetic moment to the systems, which also present half-metallic features; NGa (replacing Ga with N atom) also produces magnetic moment but the system remains semiconductor. Among the defects considered, VN and NGa have the lowest and highest formation energies, respectively. These results provide a development in defective nitride monolayers and provide a reference for extending potential applications.