Ga-vacancies and As-Ga-antisites in electron irradiated GaAs

Differently doped GaAs crystals were irradiated at 4 K with 0.4 MeV and 2.2 MeV electrons and were investigated by the Magnetic Circular Dichroism of the optical absorption (MCDA). After 0.4 MeV irradiations we observe firstly a new MCDA spectrum that can be related to vacancies on the Ga-sublattice and secondly the built-up of the antisite related complexes As-Ga - X(1). These observations show that the two remarkably different threshold energies for defect production in GaAs can no longer be attributed to defects on the different sublattices and that defects produced only for electron energies above 0.5 MeV must be attributed to complexes that result from double displacements. The production and annealing of different antisite complexes is systematically investigated.