Comparison of the surface passivation quality of SiCx films on p-type and n-type multicrystalline silicon

The passivation quality of PECVD phosphorus-doped amorphous silicon carbide films (SiCx:P) and amorphous silicon nitride films (SiNx) deposited on p-type multicrystalline silicon (mc-Si) wafers is compared, in addition, the passivation quality of amorphous silicon carbonitride films (SiCx:N) and SiNx films deposited on n-type mc-Si. The injection level (delta n) dependence of the average effective lifetime (tau(ind eff)) in mc-Si wafers passivated on botn sides is measured by the quasi steady-state photoconductance (QSS-PC) method. The spatial distribution of the lifetime is calculated from carrier density images (CDI). The effective surface recombination velocity (S(ind eff)) at the silicon surface after film deposition is very low (S(ind eff) about 15-150 cms-1) for all films. Thus, lifetime measurements on mc-Si wafers reflect directly the bulk lifetime (tau(ind vol)) of the mc-Si. The n-type wafers presented a large grain size with an average tau(ind vol) about 200-300 µs indicating an open circuit voltage (V(ind oc)) limit of about 670 mV. The p-type mc-Si wafers showed a smaller grain size with an average tau(ind vol) about 30 - 80 µs indicating an Voc-limit of about 640 mV. These wafers presented a strong increase of the lifetime in the low delta n-region most probably due to trapping effects.