Experimental and numerical study of the recovery softness and overvoltage dependence on p–i–n diode design

This work offers a reliability-oriented characterization of power p–i–n diodes turn-off transients. The softness of the turn-off and the snap-off voltage (defined as the threshold beyond which large, anomalous reverse overvoltages develop across the diode at turn-off) are investigated both experimentally and numerically for a wide set of diodes with different drift region width, resistivity and lifetime. In particular, lifetime control is obtained by electron irradiation at different doses. As a result, guidelines emerge for the design of the snubberless diode with optimum trade-off between switching speed and softness. It is also suggested that, for complete diode characterization, the well-known softness factor be accompanied by the snap-off voltage, i.e. the peak reverse voltage triggering anomalous oscillations in the turn-off transient.