A Dynamic Self-Clamping Caused by Dynamic Avalanche During the Turn-Off of PT-IGBT

A dynamic self-clamping is found during overstress turn-off of the PT-insulated gate bipolar transistor (IGBT) with a higher carrier lifetime. Theoretical analysis and numerical device simulation reveal that it is caused by the remaining plasma that cannot be completely removed due to dynamic avalanche injection. A 1-D physics-based analytical model for the self-clamping is established, and analytical results indicate that clamped voltage is inversely proportional to the initial turn-off current density and the carrier lifetime. When the dc-link voltage is larger than the clamped voltage of the device at a certain turn-off current, both terminal voltage and terminal current will be clamped, causing the device to lose control of the gate. Simulations of the multicell structure demonstrate that the avalanche-generated current filament under the self-clamping is stationary and may exist for a longer time, which is extremely likely to lead to local overheat and device destruction.