Research Of Dynamic Avalanche Mechanism And Influencing Factors For Dual GCT

Dynamic avalanche is a critical factor for the SOA of power devices,It's inevitable that dynamic avalanche occurs because the electric field is modulated by free carrier under the condition of over-stress during the turn-off of power device.These paper take 4.5kV Dual GCT as the research object.The mechanisms of the occurrence of dynamic avalanche and the mechanisms of evolution of filament are studied,and the key influencing factors of the dynamic avalanche are analyzed by Using TCAD simulator.And,to propose the corresponding measures of improvement.The main research contents are as follows.Firstly,Based on the structural characteristics and turn-off mechanism of the Dual GCT,the mechanism of occurrence of dynamic avalanche and the mechanism of generation and movement behavior of current filament are analyzed theoretically.It is pointed out that hole injection of the anode will promote the dynamic avalanche at the pn junction of the Dual GCT.Secondly,The structural model of Dual GCT is established.The mechanism of dynamic avalanche for Dual GCT is revealed by simulating and analyzing the dynamic avalanche in the process of turn-off under different over-stress conditions.The results show that the dynamic avalanche has a negative feedback mechanism in the case of over-current,which can't lead to device failure,and show that the negative feedback mechanism disappears while the Switching Self Clamping Mode(SSCM)occurs in the case of over-voltage,which may lead to the destruction of Dual GCT.Thirdly,the influence of GCT B with different carrier lifetime and different tdelay on the current filament and total power loss of the Dual GCT,as well as the influence of the Dual GCT's key structural parameters,such as,anode doping concentration,FS layer thickness and concentration,on the dynamic avalanche was analyzed,Finally,the measurements of improving dynamic avalanche capability for Dual GCT is given.The research results of this paper provide some reference value for device design of Dual GCT and application.