Photoluminescence-based dopant imaging of Ga-, P- and Sb-doped Czochralski-grown silicon wafers for solar cells

Abstract

Recharged Czochralski (RCz) silicon is now the dominant substrate for industrial photovoltaics, yet research on radial dopant uniformity remains limited. In this study, we apply high-resolution steady-state photoluminescence (PL) imaging of the doping concentration, calibrated using eddy-current resistivity measurements, to characterize radial and axial dopant distributions in RCz-grown silicon wafers doped with antimony (Sb), phosphorus (P), and gallium (Ga). Despite their markedly different segregation coefficients, all three dopants exhibit highly uniform radial concentration profiles, with only weak (<10%) reductions in dopant concentration toward the wafer edges. These trends are consistent with the suppression of radial concentration gradients by crystal-crucible counter-rotation in the RCz process. Localized variations observed in the central similar to 30 mm region are attributed to dopant redistribution driven by buoyancy-and Marangoni-driven melt convection. Axially along the length of the ingot, the wafers exhibit dopant distributions that are consistent with the combined effects of dopant segregation and evaporation: Sb-doped wafers show minimal doping variation along the ingot, whereas P-and Ga-doped wafers exhibit increasing doping concentrations toward the ingot tail. Calibrated PL measurements also reveal changes in apparent doping concentration arising from oxygen-related thermal donor (TD) formation and annihilation in Sb-doped samples after thermal treatments. These results demonstrate that RCz growth yields wafers with excellent radial dopant uniformity for the n-and p-type dopants studied here. Show more