Crystals which had been irradiated to various thermal neutron fluences were investigated by using optical absorption and positron lifetime measurements. It was found that irradiation produced a shift of the absorption edge towards longer wavelengths, and created an absorption band which was centered at 1.24eV. The absorption edge fully recovered during annealing, but the absorption band remained. The positron lifetime spectra were found to have 2 components. The longer lifetime of 300ps had an intensity that increased with fluence and fell after annealing. This component was attributed to positrons that were trapped at In monovacancy-related defects. The absorption tail was suggested to be due to optical transitions that involved vacancies which acted as acceptors, while the 1.24eV band was tentatively attributed to anion antisites.

B.Mari, F.J.Navarro, M.A.Hernandez, J.Riera: Nuclear Instruments and Methods in Physics Research B, 1996, 120[1-4], 240-3