An improved analysis of the p-n junction current-voltage (I-V) and capacitance-voltage (C-V) characteristics is proposed and applied to diodes fabricated in a variety of silicon substrates. It is shown that for state-of-the-art processing conditions the diffusion current at room temperature dominates the volume leakage current. The peripheral component, on the other hand, is governed by the surface generation in the bird＇s-beak region surrounding the complementary metal oxide semiconductor compatible diodes. Nevertheless, a small substrate effect is observed, which can only be resolved by the proposed optimized analysis. For epitaxial wafers, the presence of the highly doped substrate can significantly reduce the volume diffusion current, while for internally gettered Czochralski material the presence of a highly defective bulk region under the denuded zone enhances this current. This complicates the recombination lifetime extraction from I-V characteristics.