The defect properties of buried oxide silicon‐on‐insulator (SOI) formed by high dose O+ion implantation and annealed in the temperature range of 1150–1300 °C were examined using photoluminescence (PL) spectroscopy and transmission electron microscopy. The intensity of radiative defect levels at 0.814 and 0.862 eV measured by PL at 4.2 K was observed to decrease with increasing post‐implantation annealing temperature. A direct correlation between the radiative defect band intensities and etch defect density in the top silicon layer was observed. The correlation between defect density and PL defect band intensity was further verified by cross‐sectional transmission electron microscopy of the top silicon. This letter demonstrates for the first time the correlation between PL defect properties and microstructure of buried oxide SOI. From comparisons with radiative defect centers in oxygen precipitated and plastically deformed silicon, the radiative defect states in SOI silicon are shown to result from residual dislocations in the top silicon layer of the SOI structure.