Control of electric fields at the surface of p-n junctions

Surface breakdown or degradation resulting from the migration of surface ions are highly dependent on electric fields. As a consequence, it is very desirable to design high voltage pn junction devices so that the electric field at the surface is significantly lower than that within the body of the device. The shape, surface doping and dielectric constant at the junction-surface interface have an appreciable influence on the electric field in the space charge layer adjoining the surface of the device. Iterative solutions of Poissons equation in two dimensions have been developed which permit predictions of the surface field as a function of surface geometry and dielectric coating. Measurement of surface fields by probing the junctions are in good agreement with the calculated values.