A study was made of the electronic structure, atomic geometry, and formation energies of native defects by using first-principles total-energy calculations. The results revealed that vacancies were the predominant defects, whereas antisites and interstitials were energetically less favorable. In p-type samples, the N vacancy (a donor) had the lowest formation energy. In the case of n-type samples, it was the Ga vacancy (an acceptor). This showed that vacancies could be important for compensation. However, isolated point defects, and especially the N vacancy, could be excluded as being the source of n-type conductivity in as-grown material; contrary to general opinion.

J.Neugebauer, C.G.Van de Walle: Physical Review B, 1994, 50[11], 8067-70