The Distribution of Chromium in Multicrystalline Silicon

Metallic impurities such as chromium form Shockley-Read-Hall recombination centers in both p- and n-type silicon, limiting minority-carrier lifetimes and reducing solar cell efficiencies. Much effort has been focused on understanding the distribution and evolution of iron-silicide precipitates during phosphorous diffusion gettering. As interest in n-type silicon grows, other impurities including chromium require similar attention. We elucidate the spatial distribution of chromium-rich particles in intentionally-contaminated multicrystalline silicon using micro-X-ray fluorescence. We find that observed chromium-rich particles are, on average, smaller and in lower density than observed iron-rich particles, likely because of the lower Cr solubility and diffusivity compared to Fe. These experimental observations could enable more accurate modeling of the behavior of chromium in silicon.