What can be the optimum IGBT structure under UIS operation?

For inductive load, UIS conditions occur when the freewheeling diode in parallel with the load has just been destroyed. The energy stored in the inductor can not disappear instantaneously, hence, the associated transistor is submitted to high voltage and high current simultaneously. Based on previous studies, we analyze and try to sum up what can be the optimum IGBT structure for UIS operation. The influence of the device voltage rating, the buffer layer (punch-through and non punch-through) and the carrier lifetime (fast and ultra fast) are investigated by the help of intensive measurements. Simulation results allow pointing out the main drawback of the punch-through structure.