Gettering of Iron in Silicon Solar Cells With Implanted Emitters

We present here experimental results on the gettering of iron in Czochralski-grown silicon by phosphorus implantation. The gettering efficiency and the gettering mechanisms in a high resistivity implanted emitter are determined as a function of both initial iron level and gettering anneal. The results show that gettering in implanted emitters can be efficient if precipitation at the emitter is activated. This requires low gettering temperatures and/or high initial contamination level. The fastest method to getter iron from the bulk is to rapidly nucleate iron precipitates before the gettering anneal. Here, this was achieved by a fast ramp to the room temperature in between the implantation anneal and the gettering anneal.