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Expansion of single Shockley stacking faults (SSFs) during forward current operation is an important issue, because it decreases the reliability of 4H-SiC bipolar devices. In this paper, we propose a method for analyzing SSF dynamics based on free energy under current conduction, temperature, and resolved shear stress conditions. The driving force for dislocation dissociation reactions and formation of SSFs is incorporated into the free energy function, including chemical potential, stacking fault energy, crystallographic energy, gradient energy and elastic strain energy. The net energy gain of the chemical potential was calculated as a function of temperature and current conduction through use of the a TCAD device simulator based on the Boltzmann equation, Poisson equation and the current continuity equation concerning electron and hole distributions with self-consistency. It was confirmed that SSF dynamics can be simulated by the proposed method. It was also found that SSF formation can be attributed to quantum well variation in which electrons in n-type 4H–SiC enter SSF-induced quantum well states to lower the energy of the dislocation system.

To understand the effects of temperature and injection current density on expansion of Shockley stacking faults (SSFs) from basal-plane dislocations in 4H-SiC p-i-n diodes, the threshold current density for SSF expansion was investigated at eight temperatures by electroluminescence image observation. The threshold injection current density was found to decrease at lower temperatures and to increase at higher temperatures. We identified the origin of this temperature dependence and found that the limiting factor for expansion differed depending on the temperature.

Single Shockley stacking faults (SSFs) expand from basal plane dislocations (BPDs) under forward current operation of 4H-SiC bipolar devices, giving rise to a reliability deterioration mode called “bipolar degradation”. Several groups have proposed models for the expansion of SSFs, in which the SSFs expand when electron-hole pair recombination takes place at BPDs. Maeda proposed a formulation of SSF expansion that includes stacking fault energy. However, the mechanisms by which mechanical stress affects the expansion of SSFs are unclear. In this paper, we evaluated the “expansion threshold current” of bar-shaped SSFs in a mechanical stress field using a p-i-n diode fabricated on 4H-SiC. To confirm the effect of mechanical stress on the threshold current for bar-shaped SSF expansion, a SiC-p-i-n diode was evaluated by the four-point bending method. Experimental results show that the threshold current of SSFs decreases or increases by more than 100 A/cm2 depending on the direction of the applied stress of SSFs. This result indicates that mechanical stress is an important factor for SiC bipolar device design.