Silicon substrate effects on the current–voltage characteristics of advanced p–n junction diodes

An in-depth analysis of the forward and reverse current–voltage characteristics allows determination of the different geometrical (area, perimeter and corner) and physical (diffusion and generation) current components. This is a powerful technique to assess the silicon substrate quality. In this paper it is shown that the diffusion current of a good quality silicon p–n junction is significantly lower for an epitaxial (Epi) wafer compared to a Czochralski (Cz) wafer. This can be explained by a correction factor, F, which depends on the parameters of the highly doped substrate. The impact of the substrate is less pronounced when the leakage current is dominated by the peripheral component. Furthermore, for low reverse bias, current transients occur for large area diodes in Cz substrates. These are related to the presence of generation centres, which are absent in epitaxial wafers.