Second breakdown of IC structured power transistors

The authors attempt to characterize second breakdown as heating phenomena which can occur in one of two places, either at the p-n interface at low current or at the n-n⁺interface at higher current. The transition point between these two states occurs at a current It= qVsatNDS where the n-region field is uniform and at a voltage Vt= εsatWepijust necessary to saturate the drift velocity in Wepi.