The momentum distribution of electron–positron pairs was investigated here for the first time by measuring the 1-dimensional angular correlation of the annihilation radiation. The characteristic parameter of the electron density, r (the radius of the sphere occupied by an electron), as estimated from experimental data, differed from the rs value calculated using a standard model for non-interacting particles: rn ≈ 1.66rs, where rs ≈ 1.6568au. The chemical nature of the atoms in the environs of the annihilating positrons was deduced from the electron–positron ionic radius of Ga3+ and N5+ cores; which were determined from the characteristics of the high-momentum component of the curves of 1-dimensional angular correlation of the annihilation radiation. The analysis was based upon a comparison of the electron–positron ionic radii with standard ones. It was concluded that

positron annihilation predominated in the regions of vacancy-type so-called N antisite–vacancy complexes, [NGa+VGa].

Investigation of Vacancy-Type Complexes in GaN and AlN using Positron Annihilation. N.Y.Arutyunov, A.V.Mikhaĭlin, V.Y.Davydov, V.V.Emtsev, G.A.Oganesyan, E.E.Haller: Semiconductors, 2002, 36[10], 1106-10