Model of the redistribution of erbium during the solid-phase epitaxial crystallization of silicon

A quantitative model of the redistribution of rare-earth-ion impurities during the solid-phase epitaxial crystallization of Si layers amorphized by implantation is developed. The parameters of the model include the segregation coefficient k and the width of the transition layer. The movement of the crystallization front toward the surface is accompanied by an increase in the segregation coefficient at a rate which can be characterized by the ratio of the thickness of the recrystallization layer to the width of the transition layer. The increase in k is attributed to defect accumulation in the transition layer. In the case of a thin Er-containing amorphous layer, the segregation coefficient does not reach k=1, because the impurity is driven back toward the surface. In the case of a thicker Er-containing layer, the segregation coefficient exceeds k=1 and prevents the accumulation of impurity atoms near the surface.