Applications of Photoluminescence Imaging to Dopant and Carrier Concentration Measurements of Silicon Wafers

Photoluminescence-based imaging is most commonly used to measure the excess minority carrier density and its corresponding lifetime. By using appropriate surface treatments, this high-resolution imaging technique can also be used for majority carrier concentration determination. The mechanism involves effectively pinning the minority excess carrier density, resulting in a dependence of the photoluminescence intensity on only the majority carrier density. Three suitable surface preparation methods are introduced in this paper: aluminum sputtering, deionized water etching, and mechanical abrasion. Spatially resolved dopant density images determined using this technique are consistent with the images obtained by a well-established technique based on free carrier infrared emission. Three applications of the technique are also presented in this paper, which include imaging of oxygen-related thermal donors, radial dopant density analysis, and the study of donor-related recombination active defects. These applications demonstrate the usefulness of the technique in characterizing silicon materials for photovoltaics.