Atomic geometry and electronic structure of native defects in GaN

We have studied the electronic structure, atomic geometry, and formation energies of native defects in GaN using first-principles total-energy calculations. Our results reveal the vacancies to be the dominant defects in GaN, whereas antisites and interstitials are energetically less favorable. In p-type GaN the nitrogen vacancy (a donor) has the lowest formation energy, in n-type GaN the gallium vacancy (an acceptor). Our results show that the vacancies may be important for compensation. However, isolated point defects and particularly the nitrogen vacancy can be excluded as the source for the n-type conductivity in as-grown GaN, contrary to the generally accepted picture.