Variously doped crystals were irradiated with 0.4 and 2.2MeV electrons at 4K and were monitored by means of measurements of the magnetic circular dichroism of the optical absorption. It was found that, after 0.4MeV irradiation, a new magnetic circular dichroism of optical absorption spectrum appeared that could be related to vacancies on the Ga sub-lattice. There was also a build-up of the antisite-related complexes, AsGa-X1. These observations showed that the 2 markedly different threshold energies for defect production in GaAs could no longer be attributed to defects on the various sub-lattices, and that the defects which were produced only by electron energies above 0.5MeV had to be attributed to complexes which resulted from double displacements.

H.Hausmann, P.Ehrhart: Materials Science Forum, 1995, 196-201, 1255-60