Light induced degradation in Czochralski silicon during illuminated high temperature processing

Traditional Czochralski grown Si solar cells are known to suffer from light induced degradation (LID). The defect responsible for the LID is known to anneal out at temperatures above 200°C in the dark. This paper shows for the first time that bulk lifetime in boron doped Cz Si also degrades at 400°C and 600°C under lamp illumination in a belt furnace. In addition, both degradation and annealing mechanisms are shown to be active for the same RTP heating cycle at 200°C. As a result, a Cz Si sample can be annealed from 25i s to 44i s and degraded from a 180i s down to a 45i s effective lifetime. The bulk lifetime is fully recovered at temperatures above 300°C in the RTP and above 600°C in a belt furnace because defect annealing rate exceeds the defect formation rate. On the other hand bulk lifetime is annealed in a conventional furnace at temperatures above 200°C with no lamp illumination.