Approaches to Mitigate Edge Recombination Effects in Silicon Lifetime Samples With Emitter

Abstract

Insufficiently sized symmetric lifetime samples with pn-junction exhibit a specific injection-dependent effective charge carrier lifetime measured by photoconductance decay due to increased edge recombination, characterized by a strong decline toward low injection. In this study, various approaches are presented to suppress these edge effects in n-type Si samples with boron emitter. These approaches include edge passivation using AlOx from atomic layer deposition and the creation of an undiffused buffer layer between the central measurement area and recombination-active edges. For the latter, both an etch-back approach and a masked diffusion of the boron emitter (sunken emitter) are evaluated. Lifetime measurements and photoluminescence imaging demonstrate that the sunken emitter approach most effectively suppresses edge recombination in small-sized lifetime samples.