Reaction pathway analysis for the conversion of perfect screw basal plane dislocation to threading edge dislocation in 4H-SiC

4H-SiC has gained attention as a material for advanced power devices. In this paper, we investigate the surface effect on the conversion from screw-type basal plane dislocation (BPD) to threading edge dislocation (TED) using reaction pathway analysis. We find that the constriction of a partial dislocation pair easily occurs in the vicinity of the surface and that the constriction in the Si-face substrate is easier than that in the C-face one. Also, we find that the cross slip of a perfect screw BPD easily occurs in the vicinity of the surface and that the cross slip in the Si-face is easier than that in the C-face. In addition, we reveal that the rate-limiting step of the cross slip is the glide to shuffle-glide mix transition. We also perform molecular dynamics simulations of a perfect screw BPD-TED conversion in an off-cut substrate and confirm that spontaneous conversion occurs even at low temperature (500 K).