Towards the tailoring of P diffusion gettering to as-grown silicon material properties

The evolution of Fe-related defects is simulated for different P diffusion gettering (PDG) processes which are applied during silicon solar cell processing. It is shown that the introduction of an extended PDG is beneficial for some as-grown Si materials but not essential for all of them. For mc-Si wafers with an as-grown Fe concentration ≤10¹⁴ cm^-3, a good reduction of the Fei concentration and increase of the electron lifetime is achieved during standard PDG. For mc-Si wafers with a higher asgrown Fe concentration the introduction of defect engineering tools into the solar cell process seems to be advantageous. From comparison of standard PDG with extended PDG it is concluded that the latter leads to a stronger reduction of highly recombination active Fei atoms due to an enhanced segregation gettering effect. For an as-grown Fe concentration between 10¹⁴ cm^-3 and 10¹⁵ cm^-3, this enhanced Fei reduction results in an appreciable increase in the electron lifetime. However, for an as-grown Fe concentration >10¹⁵ cm^-3, the PDG process needs to be optimized in order to reduce the total Fe concentration within the wafer as the electron lifetime after extended PDG keeps being limited by recombination at precipitated Fe.