On the formation of vacancy defects in III-nitride semiconductors

In-grown group III (cation) vacancies (VGa, VAl, VIn) in GaN, AlN and InN tend to be complexed with donor-type defects on the N sublattice, such as ON or the N vacancy (VN). The cation vacancies and their complexes are generally deep acceptors, and hence they compensate for the n-type conductivity and add to the scattering centers limiting the carrier mobility in these materials. This work presents results obtained with positron annihilation spectroscopy in a variety of GaN, AlN, InN samples from different sources. The vacancy-donor complexes are different in these three materials, and their importance in determining the opto-electronic properties of the material varies as well. The formation of these defects is discussed in the light of the differences in the growth methods.