Spectral Characteristics and Spatial Distribution of Thermal Donors in n‐Type Czochralski‐Silicon Wafers

In monocrystalline silicon rich in oxygen, thermal donors are formed at temperatures around 450 °C. These are widely accepted to be electrically active oxygen clusters acting as double donors to the conduction band. Exposure to higher temperatures (650 °C) reportedly eliminates them. Herein, a systematic study of the spatial distribution of thermal donor formation and elimination by heat treatment at 450 and 650 °C in commercial n‐type Czochralski‐silicon wafers with high and low content of interstitial oxygen atoms are reported. Hyperspectral imaging techniques with spectral and spatial resolution are used. Thermal donors form at 450 °C in a ring‐like pattern, significantly enhanced in oxygen‐rich material. The results indicate the formation of at least six different donor clusters, leading to a strong, characteristic spectral response upon photoexcitation. The emission related to direct band‐to‐band recombination (1.100 eV) become systematically stronger upon heat treatment at 450 °C. Subsequent treatment at 650 °C rearrange the spectral response into a single, homogenously distributed, broadband emission with peak energy of 0.767 eV. The emission related to band‐to‐band recombination is significantly reduced. A previously studied emission at 0.807 eV (D1) commonly related to impurities is found, providing evidence that this signal is related to the combination of defects and oxygen. The study reports on the coupled spatial distribution and spectral characteristics of photoluminescence associated with thermal donor formation and elimination in commercial as‐cut n‐type Cz‐silicon wafers intended for use in solar cells. The results show a characteristic spectrum due to radiative recombination through traps in the bandgap with a set of individual peaks distributed as rings.