The nn+-Junction as the Key to Improved Ruggedness and Soft Recovery of Power Diodes

The effects during reverse recovery of pin power diodes are determined by free carriers and their interaction with the electric field. A density of free carriers higher than the background doping will easily occur in space-charge regions during reverse recovery of high-voltage silicon devices. As a result, a high electric-field strength combined with avalanche generation occurs at the p-n junction. However, if a second region with high electric-field strength arises at the nn(+)-junction, the situation can become critical. If the second electric-field peak can be suppressed, it is possible to make diodes that are very rugged and show a significantly improved soft-recovery behavior.