On the origin of inter band gap radiative emission in crystalline silicon

Crystal imperfections degrade the quality of multicrystalline silicon wafers by introducing alternative recombination mechanisms. Here we use non-destructive hyperspectral imaging to detect photoluminescence signals from radiatively active recombination processes over the wafer with a highly resolved spectral third dimension. We demonstrate that band-to-band recombination can be visually separated from recombination through traps across the whole surface of a wafer using hyperspectral imaging. Our samples are studied in the near infrared wavelength region, 900-1700 nm, which includes the region of the so called D-band emission lines. These constitute four resolved emission lines found in the photoluminescence spectrum of silicon, commonly related to recombination through shallow inter-band gap energy levels near the conduction- and valence band edges. The shape and structure of these emissions from our measurements suggest that all the D-lines have different origins.