Formation mechanism of dislocation half-loop array in 4H-SiC epitaxial layers: effect of triangular defects

Abstract Triangular defects in 4H silicon carbide (4H-SiC) epitaxial layers, as well as the surrounding dislocation half-loop arrays generated by basal plane dislocations (BPDs), have been directly visualized by photo-electrochemical (PEC) etching in a KOH solution. Raman spectroscopy reveals the presence of tensile stress within the triangular defect. Direct observation of threading edge dislocation (TED) pairs adjacent to the triangular defect is achieved by the PEC etching. TED pairs in the dislocation half-loop array are found to form during the epitaxy of 4H-SiC rather than being inherited from the substrate, as confirmed by two-photon excited fluorescence. Our work indicates that the internal stress originating from triangular defects plays a critical role in the nucleation and slip of BPD half-loops and the formation of the dislocation half-loop array. Our findings suggest that suppressing the formation of triangular defects and the dislocation half-loop arrays they induce can significantly reduce the BPD density in thick epitaxial layers, thereby minimizing bipolar degradations in neighboring devices and improving yield.