The high-current turn-off behaviour of trench IGBTs with dense shunting of the parasitic npn and with shallow p emitters was investigated both by simulation and experiment. In spite of current localization mechanisms (dynamic avalanche, npn transistor injection) there is no indication for a regenerative on-state under isothermal conditions, even at high temperatures up to 750K. Stable current filamentation and device destruction can only be obtained including thermal feedback. Deep trenches result in more stable behaviour, obviously from reduced maximum temperature in the source cell.
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