The electrical activity of extended lattice defects formed by interstitial oxygen precipitation in silicon is studied. Their impact on diode characteristics and on minority carrier lifetime is addressed for different initial oxygen contents and pretreatments. The carrier traps present in the substrate are studied with deep level transient spectroscopy and with photoluminescence spectroscopy. The obtained electrical results are correlated with those of structural and chemical characterization using cross‐section transmission electron microscopy and Fourier transform infrared spectroscopy. ©1995 American Institute of Physics.