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 n-n⁺ junction. The proposed destruction mode has significant similarities with previously described second breakdown at the static breakdown voltage. An approximate analytical model which was derived indicates that avalanche at the n-n⁺ junction should become unstable with a time constant on the order of nanoseconds, whereas dynamic avalanche at the p-n junction should be stable. Simulations and measurements show 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 a function of the reverse peak voltage.