Phosphorus gettering of iron by screen-printed emitters in monocrystalline Czochralski silicon wafers

In this paper, we demonstrate single-sided screen-printed emitters in thin monocrystalline Czochralski silicon (Cz-Si) wafers with an improved gettering of iron compared with conventional double-sided POCl3 emitters. The phosphorus dopant pastes used have to be chosen carefully to provide a sufficiently low emitter sheet resistance and to avoid iron contamination. The iron concentration is determined in a non-destructive way from the minority carrier lifetime obtained by quasi-steady-state photoconductance measurements, down to levels not yet demonstrated for screen-printed emitters. In addition, the well-known metastable boron-oxygen complexes in Cz-Si have been transferred into a stable state by light-induced degradation prior to these measurements. Copyright (c) 2012 John Wiley & Sons, Ltd.