Imaging of Metastable Defects in Silicon

Photoluminescence imaging is able to provide quantitative information about carrier lifetime in silicon wafers. Recently, this technique has been applied to measure the distribution of iron and chromium point defects in p-type silicon. In this paper, we summarize the state of the art and extend the impurity analysis by photoluminescence imaging with the detection of the boron-oxygen defect. Solar cells from p-type Czochralski silicon material are mostly limited by this defect, but its impact may also be significant for multicrystalline silicon. For the presence of several metastable defect species, we demonstrate the preparation of a specific state of the metastable defects with appropriate conditions for temperature and illumination and show that the respective impurity concentrations can be determined in parallel. We complete the analysis by discussing the effects of lateral carrier diffusion on the measurement result.