On the destruction limit of Si power diodes during reverse recovery with dynamic avalanche

The reverse recovery destruction limit of 3.3 kV fast recovery diodes was investigated by measurements and device simulations. Based on a good agreement between the measured destruction limit and current filamentation in simulations, it is proposed that the destruction is triggered by the onset of impact ionization at the nn(+) junction. The proposed destruction mode has large similarities with previously described second breakdown at the static breakdown voltage. An approximate analytical model which was derived indicate that avalanche at the nn(+) junction should become unstable with a time constant on the order of nanoseconds, whereas dynamic avalanche at the pn junction should be stable. Simulations and measurements give at hand that the reverse recovery safe operating area depends on the n-base width. An approximate equation is proposed to determine the minimum n-base width required for a nondestructive reverse recovery with dynamic avalanche as function of the reverse peak voltage.