Research On Dynamic Avalanche Failure Mechanism Of GCT

Dynamic avalanche is a key factor in affecting the reliability of the power semiconductor device.With the increasing range of applications of integrated gate commutated thyristor(IGCT)in recent years,the failure problem is more and more.Therefore,the research on the inducing factors and failure mechanism of dynamic avalanche is more urgent and important.This paper focuses on the 4500 V AS-GCT,the mechanisms of occurrence and failure of dynamic avalanche are studied,and the influence factors of the dynamic avalanche are analyzed by Sentaurus simulator and the related theory.The main contents are as follows.Firstly,the mechanism of dynamic avalanche is analyzed deeply according to the structural features and physical mechanism of GCT,and then the turn-off characteristics of GCT,the appearance and movement of current filament are simulated by device simulator.In addition,the two-dimension analytical model of plasma fronts velocities is built up.It is revealed that the mechanism of GCT dynamic avalanche and the results show the feedback mechanism exists in dynamic avalanche of GCT.Secondly,the device structural model of two cells connected in parallel and test circuit is built,the distributions of current density,the electric field strength and plasma are simulated.The results show that current filament first gather in the outer ring,which may cause the GCT to be re-triggered when current filament moves through the p-base region below the cathode;The failure mechanism of GCT turn-off at high voltage is analyzed,the results reveal that the negative feedback mechanism of dynamic avalanche of GCT may disappear and voltage clamping phenomenon appears leading to the failure of GCT.Thirdly,it was analyzed that what factors affect dynamic avalanche,including the depth of the deep p base,the doping concerntration and thickness of anode and FS layer,lifetime of the minority carrier and the related parameters in the turn-off circuit,such as stray inductance Liand clamp inductance L?,and so on.Finally,measures on suppressing the occurrence of dynamic avalanche are put forward.The research results in this paper are meant to offer some references for the device design and applications of IGCT.