Avalanche breakdown of high-voltage p-n junctions of SIC

Design rules of p-n junctions must pay special attention to the parameters that control the electric field at the surface in order to avoid surface breakdown. Moreover, they must be compatible with the available technology. In this sense, negative bevelling has been the solution traditionally used in high-voltage diffused p-n junctions in silicon. Silicon carbide possesses a breakdown electric field one order of magnitude higher than that of silicon and this property endows this material with high-voltage capability. However, technological problems limit its potential applications. The difficulty of the diffusion process forces the production of p-n junctions by in situ doping during the growth of epitaxial layers, resulting in abrupt junctions. In this situation, negative bevelling is not very effective for lowering the electric field at the surface but reduces the breakdown voltage. On the other hand, surface charges at the oxide/semiconductor interface degrade the breakdown voltage further. Therefore, since intrinsic SIC properties run into technological limitations, it is important to evaluate the real potential for high-voltage diodes in SiC. For this purpose, the proper choice of SiC ionization coefficients is relevant.