Iron concentration determination

With the MDPingot and MDPmap series it is possible to measure the iron concentration in bricks and wafers fully automated and with a very high resolution.

Lifetime measurements before and after iron boron pair dissociation is a widely used method for iron determination in silicon wafers.

In boron doped silicon with a high doping concentration, as it is used for PV applications nearly 100 % of the electrical active iron is present as FeB pairs. With light of sufficient energy these pairs can be dissociated in Fe_i and B. This process is reversible and after some time all FeB pairs are associated again. FeB and Fe_i have different recombination properties, so that the dissociation has an effect on the measured lifetime. With this effect the iron concentration can be determined via:

For the iron determination a calibration factor C is used, which depends on the injection, doping concentration and trap concentration, which has to be considered especially in Multicrystalline silicon. With MDP a determination of the iron concentration is possible for mc- and mono-Si with a high resolution and thanks to simulations and years of research, also with a high accuracy.