Morphological and microstructural analysis of triangular defects in 4H-SiC homoepitaxial layers

The surface morphologies and microstructures of triangular defects in 4H-SiC homoepitaxial layers were investigated by laser confocal microscopy before and after molten KOH etching and microwave plasma etching. Three different triangular defects, namely TD-I (grains), TD-II (micro-pits), and TD-III (washboard-like defects), were analyzed. After molten KOH etching on the Si-face and plasma etching on the C-face, TD-I is identified to be bounded by one partial dislocation (PD) on each side. Simultaneously, multiple etch pits of PDs are lined up along the sides of the triangle. In addition, TD-II and TD-III are generated due to the micropipes and dislocations in the substrate, respectively. In order to investigate the formation mechanisms of complex microstructures of triangular defects, selected triangular defects are characterized by high-resolution transmission electron microscopy, micro-Raman spectroscopy, and photoluminescence spectroscopy. Results indicated that all the triangular defects consist of 3C-SiC or Frank-type SFs. Furthermore, {111} 3C-SiC twins are observed inside the TD-III, and the 3C/4H boundaries exhibited a periodic structure in which each cell consists of 12 basal planes.