Insights into Bulk Defects in n-type Monocrystalline Silicon Wafers via Temperature-Dependent Micro-Photoluminescence Spectroscopy

In this study, we use temperature-dependent microphotoluminescence spectroscopy to investigate non-uniform bulk defects in -type Czochralski and float-zone silicon wafers. For both wafer types, we observe defect photoluminescence (PL) with peak energy between 0.78 eV and 0.85 eV emerge as the temperature is decreased from 300 K to 80 K, along with an associated 10-100 times reduction in the band-to-band (BB) PL. This similarity in the shape of the spectral PL between the two wafer types suggests that the origin of the defects may be related. For the float-zone wafers, the defect PL is present even in regions appearing bright in conventional band-to-band PL imaging, suggesting that the bulk defect exists across the entire wafer, but is spatially inhomogeneous. Defect parameters are extracted by fitting the ratio of the integrated defect to band-to-band PL ratio using a modified Arrhenius equation derived from the ShockleyRead-Hall defect theory. We determine similar defect parameters for the FZ wafer within the bright and dark regions: a single defect species located at 150 to 160 meV from the valence band-edge and a capture cross-section temperature-dependence following an inverse power law with exponent of approximately 2. For the Cz wafer the defect is located 325 meV from the valence band-edge, as expected from the peak PL position, and a capture cross-section temperature exponent of approximately 2.5 was determined. This suggests that a different recombination process is responsible for the same defect PL band in each wafer type.