Edge breakdown in mesa diodes

An analysis of the current flow in a mesa diode shows that this diode suffers from similar limitations in breakdown voltage as the planar diode due to radial current flow at the diode edge. A theoretical analysis of the breakdown voltage of this structure shows that careful tailoring of the doping profile is essential to obtain bulk breakdown in IMPATT and TRAPATT mesa diodes. Experimental results from a great number of wafers strongly support this theoretical model. Band bending at the surface or microplasmas due to point defects do not satisfactorily explain the too low or badly defined breakdowns observed in our mesa diodes.