The influence of doping inhomogeneities on the reverse characteristics of semiconductor power devices

Failure of the reverse characteristic of power devices may be caused by an increase of field strength due to doping inhomogeneities. A numerical program has been developed to calculate the effect of various types of perturbations on the maximum occurring field strength and on the shape of the space charge region. Three-dimensional calculations show that the influence of inhomogeneities can partly be compensated by the surrounding material. On the other hand, spikes of the diffusion front or p-islands with a high doping concentration inside the lowly doped n-region may cause an increase of field strength, which is not expected from the one-dimensional model.