The impact of germanium doping on the dislocation distribution in directional solidified mc-silicon

In this paper experimental results on the effect of the Ge doping on the distribution of dislocations in directional solidified multi-crystalline (mc) Si are presented. The dislocation density distribution is analyzed on the basis of the average dislocation density and the cumulative probability by means of etch pits counting via optical auto-focus (AF) microscope and the Photovoltaic (PV) scan method. The Ge doped ingots show a significantly lower average dislocation density and dislocations are more homogeneously distributed in the Si matrix, whereas the undoped ingot contains large areas of accumulated dislocations. Apparently, the overall dislocation density is reduced by the induced strain field and the lower mobility of dislocations due to the pinning effect.

► Dislocation density in mc-Si is reduced by 50% due to germanium doping.
► More homogeneous dislocation distribution due to germanium doping.
► Dislocation reduction is an direct effect of the induced strain field.
► Dislocation reduction is not an indirect effect of oxygen or precipitates.