Phase field model of single Shockley stacking fault expansion in 4H-SiC PiN diode

Abstract

Expansion of a single Shockley stacking fault (SSF) during forward-current operation decreases the reliability of 4H-SiC bipolar devices. We propose a practical method for analyzing the defect evolution of SSF expansion based on free energy according to current density, temperature, and resolved shear stress conditions. The free energy includes chemical potential and elastic strain energy. Specifically, the chemical potential is related to the driving force for the formation of SSFs by temperature and current, and the elastic strain energy corresponds to the driving force for dislocations that form SSFs under the applied stress. It was confirmed that the proposed multiphysics method could well simulate SSF evolution when stress and current were applied. Furthermore, the results suggest that quantum well action, in which electrons in n-type 4H-SiC enter SSF-induced quantum well states to lower the energy of the dislocation system, affects the driving force of SSF formation.

Combined FEM and phase field method for reliability design of forward degradation in SiC bipolar device

“…Preliminary preparation: create the response surface corresponding to the PF model. 18) Step 1: Establish the design variables of the power module.…”

“…We previously proposed a phase field (PF) method based on the timedependent Ginzburg-Landau (GL) equation by such a demand to analyze the defect evolution in SSF expansion based on free energy according to RSS and carrier density, which depends on current density and temperature. 18) Although the PF method is capable of analysis and evaluation within a narrow range, as a design method, it is still insufficient for analysis of entire devices and analysis under practical usage conditions, owing to the huge amount of analysis time required.…”

“…In this study, we propose a design method for analyzing the critical condition dependent on the electrical, thermal and mechanical quantities due to SSF expansion by using a combined method with a multiphysical finite element method (FEM) and PF model based on the time-dependent GL equation. We applied our previously proposed method 18,19) to obtain the SSF expansion rate from the PF model and developed a response surface corresponding to the PF model dependent on the electrical, thermal, and mechanical quantities obtained by multiphysical FEM analyses in order to efficiently obtain the SSF expansion rate in a 4H-SiC bipolar diode under practical usage conditions. The initial stage of SSF expansion was targeted because it is the least expanded stage in the formation of triangular or bar-shaped SSFs.…”

Kink Migration along 30° Si‐Core Partial Dislocations in 4H‐SiC

“…[3][4][5][6][7] Therefore, studies of SSF nucleation and expansion have drawn the attention of many researchers. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] However, in spite of numerous investigations understanding the SSF behavior is still insufficient and many fundamental questions still remain to be explored. It has been well established that SSFs can be introduced at room temperature in power devices at high forward currents [3][4][5][6][7][8]19,22] or under electron beam or optical irradiation.…”

“…[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] However, in spite of numerous investigations understanding the SSF behavior is still insufficient and many fundamental questions still remain to be explored. It has been well established that SSFs can be introduced at room temperature in power devices at high forward currents [3][4][5][6][7][8]19,22] or under electron beam or optical irradiation. [10][11][12][13][14][15][16][17] As the SSF expansion in 4H-SiC under mechanical shear stress was observed only at temperatures exceeding 250 °C, [13,18] their expansion at room temperature suggests a strong effect of excess carriers on the mobility of partial dislocations (PDs) driving the SSF expansion (Si-core 30°PDs [23][24][25] ).…”