Understanding the breakdown asymmetry of 4H-SiC power diodes with extended defects at locations along step-flow direction

Abstract

Power electronic devices for high-voltage applications prefer wide-bandgap semiconductors such as silicon carbide, whereas the immaturity of epitaxial growth technology introduces many extended defects, some of which are crucial to the electrical performance of fabricated devices. Therefore, it is much expected to find out some deep relation between extended defects and device performance. In this work, based on comparisons of breakdown behaviors of 4H-SiC power diodes with or without extended defects of different types, the importance of several features of the extended defect, including the distance, length, and orientation, is reported. Besides, based on the experimental results from dark-field microscopy, near-ultra-violet photoluminescence and topography, and theoretical analysis with numerical calculations, the mechanism of a particular asymmetric breakdown behavior in 4H-SiC devices along the step-flow direction is revealed, which originates from the prevalent step-controlled epitaxy technology for the commercial 4H-SiC epitaxial wafer. With the proposed result and understanding, it is possible to achieve a higher yield in production at a similar material cost.