IMPROVEMENT OF DIFFUSION LENGTH IN POLYCRYSTALLINE PHOTOVOLTAIC SILICON BY PHOSPHORUS AND CHLORINE GETTERING

Results of chlorine and phosphorus gettering of photovoltaic (PV) poly crystalline silicon are presented. Using surface photovoltage (SPV) di ffusion length (L) measurements, it has been established that PV polys ilicon is very inhomogeneous and gettering only improves L values in r egions in which L is relatively high and a large amount of nonprecipit ated Fe and Cr is present. In regions with low L, nonprecipitated Fe a nd Cr were not detected in as-grown polysilicon and gettering did not cause any substantial improvement in L values. It is conceivable that recombination in these regions is controlled by grown-in defects.