Light emitting diodes with an active defect-rich region produced by oxygen implantation and a subsequent multistep annealing of silicon wafers were investigated by means of transmission electron microscopy, SIMS, capacitance voltage, deep level transient spectroscopy, electroluminescence (EL), and cathodoluminescence (CL) techniques. The properties of two groups of n-based samples with and without thermal pre-treatment at 1000 °C for 15 min were compared regarding their defect structure, defects electrical activity, luminescent spectra as well as the impact of prolonged intense electron irradiation. The observed difference in the properties of such groups was explained by a difference in the density and oxygen content of oxygen-related defects. A significant distinction between EL and CL spectra at low excitation levels was found and interpreted to be due to particular defect kinds in near-surface and the deepest layers of the implanted region. The blue shift of EL spectra upon excitation increase reported previously is explained by the increase of penetration depth of the holes and specific depth distribution of the defects of different kinds.