Minority Carrier Diffusion Length Degradation in Silicon:Who is the Culprit?

摘要

The influence of transition metals on minority carrier diffusion length in silicon is discussed. It is shown that transition metals easily precipitate on silicon lattice microdefects. These precipitates can not be easily dissolved, which makes gettering procedure ineffective. This conclusion is confirmed by experiments on FZ, CZ and photovoltaic silicon, discussed in this paper. The recombination activity of interstitial copper and its capture cross-section for electrons are determined. The recombination activity of interstitial and precipitated copper and iron are compared. It is shown that the precipitates of copper have much higher recombination activity than the interstitial copper, whereas iron is very active in both precipitated and interstitial form.