High-temperature physical effects underlying the failure mechanism in thyristors under surge conditions

With the aim of assessing the role of various high-temperature physical effects in the transient electrothermal behavior of thyristors under surge current conditions, the distribution of carriers concentration in the bases of a thyristor at temperatures close to the threshold of the device destruction has been estimated in a quasi-static approach. It was found that the carriers concentration in almost the entire bases region is well below the level when the Auger recombination and carrier-carrier scattering are important. It is shown that the drastic fall of mobilities µ at elevated temperatures T is responsible for the removal of both Auger recombination and carrier-carrier scattering from the bases of devices. Becoming the dominant factor regulating the carriers dynamics in the bases, it is precisely the dependence which renders important the contribution of intrinsic carriers in the inhomogenous supply of bases with mobile carriers under strong power dissipation. These high-temperature physical aspects axe incorporated into an unitary presentation of phenomenology of thyristors failure under surge current conditions. The theoretical/experimental background confirming the validity of the failure model presented herein is also outlined in this work. It is shown that the advanced model allows for a computer-based prediction of the transient electrothermal behavior of power thyristors under various surge ratings.