Field distribution near the surface of beveled P-N junctions in high-voltage devices

A new method for investigating the field distribution near the surface of p-n junctions is presented. The results show that for negatively beveled junctions, an absolute field maximum exists underneath the surface. This field maximum rather than the field on the surface determines the breakdown voltage of the device. The dependency of the maximum field on various device parameters as base resistivity, bevel angle, and steepness of the doping profile is analyzed. In addition, the influence of surface charges and dielectrics is investigated. Finally, the advantages of positive bevel angles with respect to negative ones are demonstrated. The theoretical results were verified by potential probing measurements on the surface of high-voltage devices.