Field calculations of planar diffused structures with field limiting rings

A theoretical and experimental study of planar diffused structures with field limiting rings is presented. The basis of the theory is a new type of depletion layer logic which allows making field calculations in back-biased structures with floating field rings in the presence of surface charge. Using the results of the field calculations, avalanche multiplication factors are calculated along the gradient of the potential. Circular planar rectifiers with one field limiting ring were fabricated to test the theoretical results. The dependence of the field ring potential versus the applied potential and the avalanche breakdown voltages for theory and experiment were within ten percent. A result of the study is that the field ring junction is not completely effective in assuming increases in applied voltage beyond the punch-through voltage to the field ring.