Effect of the load inductor on the avalanche ruggedness of 1200-volt silicon diodes during unclamped inductive switching

This paper investigates the avalanche robustness of high-voltage silicon PiN diodes under unclamped inductive switching (UIS) conditions. Devices were experimentally tested across a wide range of load inductances. A pronounced reduction in robustness - both in time-to-failure and in maximum avalanche current - was observed at low inductance values, deviating from previously reported monotonic trends. These results indicate the presence of an additional electrically driven failure mechanism, distinct from the classical energy-driven avalanche failure. Based on the experimental evidence and failure analysis, two complementary failure mechanisms are proposed to explain the observed behavior: (i) an energy-driven mechanism, supported by TCAD simulations, and (ii) an electrically driven mechanism, for which a working hypothesis is formulated based on prior literature.