Influencing factors on the formation of the low minority carrier lifetime zone at the bottom of seed-assisted cast ingots

The effects of height of remaining seed, seed type, and crucible purity on the length of the low minority carrier lifetime zone (i.e., red zone) at the bottom of seed-assisted cast ingots were investigated. The red zone length at the bottom is proportional to the height of the remaining seeds. Only very little difference in the length of the bottom red zone was found in the quasi-single-crystal silicon (QSC-Si) bricks between using normal single-crystal seeds and recycled seeds, while the use of particle seeds resulted in a longer bottom red zone compared with using block seeds. Furthermore, a high-purity crucible does not result in a significant reduction in the height of bottom red zone in the QSC-Si ingot, although it results in a much shorter bottom red zone in the conventional mc-Si ingot.