Structural Stability of Vacancy and Substitutional Defects in g-GaN: A First-Principles Study

Herein, the first-principles calculations of defected monolayer graphene-like gallium nitride (g-GaN) were elucidated. The optimized geometric revealed that the nearest-neighbor distances of N-N (between N atoms) and Ga-Ga (between Ga atoms) were narrowing in most configurations. Interestingly, the VGa has a similar atomic symmetry as the pure g-GaN, which is D3h. Most defected configurations are degraded into C2V symmetries, while the Stone-Wales configuration has the lowest symmetry of CS. The formation energies of V­­Na systems are lower, which implies better energetic stability. For the divacancies, the VGa system is more stable than the V­­Na system. Moreover, the Stone-Wales configuration is energetically more stable than the interchange configuration. Furthermore, the reaction coordinates represent the geometric evolution of each defected system. The result revealed that the N-atoms are consistent with moving outward while the Ga-atoms move inward only for monovacancies and divacancies configurations. In contrast, the N-atoms move inward while the Ga-atoms move outward for substitutions, interchanges, and Stone-Wales configurations. We believe that this finding will be beneficial as the groundwork for future 2D g-GaN-based semiconductor devices. HIGHLIGHTS The V­­Na defective system is more stable than the VGa system in monovacancies and substitutions. The VGaGa defective system is more stable than the V­­Na system in divacancies. The Stone-Wales system is a stable configuration with a Cs symmetry. GRAPHICAL ABSTRACT