Optimization of diodes using the SPEED concept and CIBH

The surge current ruggedness of free-wheeling diodes can be improved by implementing the SPEED concept (Self-adjusting P Emitter Efficiency Diode). Experiments show that the switching ruggedness of such a diode is worse than that of a conventional diode. Simulations indicate that during diode turn-off filaments are pinned at the cathode side. These filaments can be avoided by implementing CIBH (Controlled Injection of Backside Holes). It turns out that a necessary additional measure is to fully embed the p⁺-areas of the SPEED anode in the low-doped p-type area to avoid high electrical field strengths and current crowding at the anode side. Combining these measures, the appearance of current filaments with an extremely high current density and their pinning to a certain area in the device during the turn-off period can be avoided.