Defect structure and electric properties of n-type silicon samples subjected to multienergy oxygen implantation and subsequent multistage thermal treatments at different high temperatures and durations are investigated with the help of transmission electron microscopy (TEM), capacitance–voltage (C(V)), and deep level transient spectroscopy (DLTS) techniques. Well spatially separated layers in the depth consisting of three predominant types of defects—threading dislocations (TDs), oxygen precipitates (OPs) together with diverse extended structural defects and OPs only—are observed with TEM. While the properties of DLTS spectra from the layer with TDs coincide well with dislocation-related ones reported in numerous previously published articles, the spectra from the OP layer are found to show unusual distinct property: the low-temperature tail of DLTS peak does not or very weakly depend on the rate window. A simplified semiquantitative model is proposed based on a big positive charge of OP layer revealed from C(V) measurements. The model explains the unusual property to be due to an increase of the Coulomb-like attractive potential upon electron emission from the electronic states of the OPs giving rise to logarithmic emission kinetics.