Photoluminescence Spectroscopy of Thermal Donors and Oxygen Precipitates Formed in Czochralski Silicon at 450 °C

Photoluminescence spectra have been measured at 80 K in Czochralski-grown silicon wafers annealed at 450 °C, causing thermal donor and oxygen-precipitate generation. Six subbandgap luminescence peaks were identified after the annealing. One peak, centered at 1206 nm, was found to increase with a similar time constant to the thermal donor concentration measured by changes in the resistivity. We propose that the other five peaks are related to the formation of oxygen precipitates (OPs), or their nuclei. These peaks remain after a thermal donor annihilation (TDA) step, while the 1206 nm peak disappeared. This is consistent with our previous observations that the growth of OPs occurs concurrently with the growth of thermal donors at low temperatures. The annihilation of the thermal donors leads to an incomplete recovery of the interstitial oxygen concentration, consistent with the formation of precipitates. Recombination-active ring-defects formed during the annealing also remain after TDA.