Influence of heterogeneous profiles in carrier density measurements with respect to iron concentration measurements in silicon

Carrier density is a frequently examined parameter for silicon material characterization especially to determine carrier lifetime. Typically integrated values are obtained which ignore nonhomogeneities in the depth dependent carrier profile and result in mean values for lifetime and injection density. Due to the averaging together with nonlinear recombination processes, these values may be subjected to substantial systematic errors. This work demonstrates the effect on iron concentration measurements which are based on the comparison of carrier lifetime measurements before and after light induced splitting of FeB pairs. Although this technique has been proven to be very sensitive, simple, and thus attractive, systematic quantitative errors are revealed in this work which are inherent to this method. It is demonstrated that the errors, while small for certain conditions, may be substantial in many practical cases. Simulations based on the calculation of carrier profiles and virtual measurements provide a tool to estimate the influence of material and setup parameters to the total systematic error. A correction method is developed from this analysis.