Absolute standard of diffusion length and lifetime of minority charge carriers in single-crystal silicon

A substantial difference in electron recombination cross sections on Fe–B complexes $(\sigma_1)$ and on activated iron ions $(\sigma_2)$ in boron-doped single-crystal silicon is used to independently determine the lifetime of electrons in the standard $T_{st}$ using the surface photo-emf method. Pairs of values of the lifetime $T_1$ and $T_2$ before and after the decomposition of the Fe–B complexes were measured for each of 600 ingots at arbitrary diffusion length $L_{cal}$ for the calibrating specimen and were placed on the plane $(T_1, T_2)$. At the boundary of the region filled with the points, ingots are presented that are only contaminated with iron ions, so that $T_2/T_1= \sigma_1/\sigma_2$. The true values of $L_{st}$ and $T_{st}$ of the calibrating specimen and the ratio $\sigma_1/\sigma_2$ = 12.5 $\pm$ 0.5 are determined by selecting a new value of the diffusion length for the calibrating specimen, which straightens the boundary of the region filled with the points after the recalculation of the values of $T_1$ and $T_2$.