Positron annihilation was used to study 2MeV 4He+ irradiated and subsequently rapid-thermal-annealed InN grown by molecular-beam epitaxy and GaN grown by metal-organic chemical-vapour deposition. The irradiation fluences were in the range of 5 x 1014 to 2 x 1016/cm2. In vacancies were introduced during irradiation, at a rate of 100/cm, with their concentration saturating in the mid-1017/cm3 range at an irradiation fluence of 2 x 1015/cm2. The annealing, performed at 425 to 475C, was observed to result in an inhomogeneous redistribution of the In vacancies. The behaviour was opposite to GaN, where Ga vacancies were introduced at a much higher rate of 3600/cm showing no detectable saturation. About half of the Ga vacancies were found to recover in the annealing, in agreement with previous studies, while the remaining Ga vacancies undergo no spatial redistribution.

Irradiation-Induced Defects in InN and GaN Studied with Positron Annihilation. F.Reurings, F.Tuomisto, W.Egger, B.Löwe, L.Ravelli, S.Sojak, Z.Liliental-Weber, R.E.Jones, K.M.Yu, W.Walukiewicz, W.J.Schaff: Physica Status Solidi A, 2010, 207[5], 1087-90