Experimental results obtained with positron annihilation spectroscopy in room-temperature electron-irradiated n-type ZnO and GaN were presented. The cation vacancies acted as important compensating centres in 2MeV electron-irradiated samples, even though their introduction rates were different by 2 orders of magnitude. In addition, negatively charged non-open volume defects that also compensated the n-type conductivity were produced together with the cation vacancies at similar introduction rates. The low introduction rates of compensating defects in ZnO demonstrated the radiation hardness of the material. Isochronal thermal annealing was performed to study the dynamics of the irradiation-induced defects. In 2MeV electron-irradiated ZnO, all the defects introduced in the irradiation disappeared already at 600K, while 1100K was needed in GaN. Several separate annealing stages of the defects were observed in both materials, the first at 400K.

Defect Studies in Electron-Irradiated ZnO and GaN. F.Tuomisto, D.C.Look, G.C.Farlow: Physica B, 2007, 401-402, 604-8