The measurements of 1-dimensional angular correlation of the annihilation radiation were carried out for BN, AlN, and GaN as well as for some related materials that were used as the reference samples for the analysis of results. The electron–positron ion radii reconstructed by 1-dimensional angular correlation of the annihilation radiation for the cation and anion sub-lattices of the nitrides as well as the estimated average electron density around the positron suggested that: (a) the positron annihilates in the vacancy complexes NGaVN in GaN and NAlVN in AlN, and (b) the cation nearest neighbors are, probably, shifted inward to the VN vacancy where the electron density was sufficiently lower in comparison with that estimated for the bulk.

Positron-Sensitive Vacancy-Type Centers in the Nitrides - 1D-ACAR Data. N.Y.Arutyunov, V.V.Emtsev, A.V.Mikhaĭlin, C.J.Humphreys: Physica B, 2003, 340-342, 412-5