Positron annihilation spectroscopy, supported by ab initio theory, was applied to verify the decoration of Ga vacancies in GaN by oxygen and hydrogen. The results indicated that the Doppler broadening measurement of electron momentum distribution was sensitive enough to distinguish even between N and O atoms neighbouring the Ga vacancy. Isolated VGa in electron irradiated GaN and VGa-ON complexes in highly O-doped high-purity GaN were identified. Evidence of H decoration of Ga vacancies was obtained in epitaxial GaN grown by metal-organic chemical-vapour deposition.

Direct Evidence of Impurity Decoration of Ga Vacancies in GaN from Positron Annihilation Spectroscopy. S.Hautakangas, I.Makkonen, V.Ranki, M.J.Puska, K.Saarinen, X.Xu, D.C.Look: Physical Review B, 2006, 73[19], 193301 (4pp)