A boron depletion layer was formed on a silicon substrate, due to the presence of a silicon oxide layer, in which the solubility of boron was higher than that in the silicon substrate. This silicon oxide layer was formed during the boron diffusion process employing the BBr3 solution. To avoid the formation of this silicon oxide layer, a silicon nitride layer was used as a reaction barrier on the surface of the silicon substrate. A 500 Å thick SiNx layer deposited by PECVD on the silicon substrate was found to prevent the formation of the silicon oxide and resulting boron depletion layer on the silicon substrate. The PC1D simulation suggested that preventing the formation of this boron depletion layer by using SiNx as a reaction barrier could enhance the solar cell conversion efficiency by 0.9% in an absolute value.

Boron Diffusion into Silicon Crystal with SiNx Layer as a Reaction Barrier. S.Yang, Y.K.Kim: Solar Energy Materials and Solar Cells, 2010, 94[12], 2187-90