Porous silicon gettering

We have studied a novel extrinsic gettering method that uses the large surface areas produced by a porous-silicon etch as gettering sites. The annealing step of the gettering used a high-flux solar furnace. We found that a high density of photons during annealing enhanced the impurity diffusion to the gettering sites. We used metallurgical-grade Si (MG-Si) prepared by directional solidification casting as the starting material. We propose to use porous-silicon-gettered MG-Si as a low-cost epitaxial substrate for polycrystalline silicon thin-film growth for solar cells.