Recombination centres related to Fe complexes in p type Si are studied by carrier lifetime measurements using non-destructive microwave and light induced absorption techniques. The cross correlation of lifetime, density of electrically active Fe species, and structural defects is used to investigate the transformation and the precipitation ofindiffused Fe. The recombination activity of Fe related defects is found to depend on the injection level of excess carriers. Both thermal and photoactivation mechanisms are employed to decompose Fe-B pairs and to study the impact on the recombination time. The increase of high level injection lifetime due to photodissociation ofFe-B pairs is explained by a more efficient recombination via an acceptor level at E C -0.29 eV which has been derived from the temperature dependence of carrier lifetime. The mechanism ofa recombination enhanced defect reaction is discussed on the basis of the experimental observations. MST/3312