First-principles density-functional theory calculations were performed in order to investigate the structural and electronic properties and the formation energies of N vacancies in wurtzite InN. An extensive and systematic study was made of the favorable atomic and electronic configurations of up to 6 vacancies in large super-cells. The isolated vacancy acted as a donor in a p-type material where there was very little interaction between the singly positive charged vacancies. Their spatial distribution was therefore predicted to be a random arrangement of single defects. However, in more n-type material, the neutral charge state became favored and it was found that the vacancies then preferred to be situated close to one another on the nearest-neighbor (like-species) sites; forming vacancy complexes or clusters. In the highest positive charge state of the complexes, the clustering was unstable with respect to isolated single positive charged vacancies. However, the negatively charged and lower positively charged (e.g., 1+ and 2+ charge states for three N vacancies) complexes also exhibited an attractive interaction between the vacancies, thus also favoring clustering. The formation of such N vacancy clusters gave rise to local In-rich regions with metallic-like bonding. The effect that these defect structures had upon the nature of the electronic states in the region of the band-gap was considered.

Nitrogen Vacancies in InN - Vacancy Clustering and Metallic Bonding from First Principles. X.M.Duan, C.Stampfl: Physical Review B, 2008, 77[11], 115207 (9pp)