Electrical properties and microstructure of crystalline silicon ingots grown from quartz crucibles with and without diffusion barriers

Abstract

Three hybrid ingots, where half the seed area was filled with fluidized bed reactor granules for high-performance multicrystalline silicon growth and the other half with monocrystalline slabs for mono-like growth, were made. The ingots were solidified in quartz crucibles with two different diffusion barriers and one reference crucible with no diffusion barrier. The material quality of these three ingots was compared with respect to minority carrier lifetime and crystal structure. High purity silica was used in one diffusion barrier, while a fraction of high purity quartz sand was mixed with such silica in the second diffusion layer. High purity quartz sand was mixed in to further increase the purity of the diffusion barrier, thus, reduce the low lifetime regions (or red-zones). The results indicate that the diffusion barriers between the quartz crucible and the directionally solidified silicon ingots reduce the extent of the red-zones, which implies that diffusion barriers aid in decreasing the amount of metallic impurities (particularly Fe) implemented into the silicon ingot. No visible changes to the crystal structure were observed between the two ingots with diffusion barrier.