Origin and Generation Process of a Triangular Single Shockley Stacking Fault Expanding from the Surface Side in 4H-SiC PIN Diodes

Abstract

A triangular single Shockley stacking fault (1SSF) in 4H-SiC, expanding from the surface to the substrate/epilayer interface, was investigated. The triangular 1SSF was observed during electroluminescence examination of PIN diodes that had line-and-space anodes with open windows. The threshold current density of the 1SSF expansion was comparatively intermediate, and differed from that of a 1SSF that expanded from a basal plane dislocation (BPD) that had penetrated from the substrate into the epilayer, and from that of a 1SSF that expanded from a BPD that had converted into threading edge dislocations (TEDs) at the substrate/epilayer interface. No BPDs or surface damage such as cracks were observed by photoluminescence imaging, synchrotron x-ray topography imaging, or scanning electron microscope imaging near the origin of the expansion region. High-resolution observation using cross-sectional transmission electron microscopy showed that a partial dislocation (PD) was present on the basal plane and two inclined TEDs were present on both sides of the PD. A g·b analysis showed that this dislocation had a Burgers vector of ± (1/3) [11$\overline{2}$0], and it was estimated to be a combination of a TED-BPD-TED structure with a short BPD before expansion. Therefore, the triangular 1SSF from the surface side can be explained to have expanded from this BPD. Furthermore, considering the possibility of the BPD-TED conversion at the epitaxial growth process, the TED-BPD-TED dislocation was speculated to have formed after epitaxial growth. The perfect control of the forward voltage degradation of 4H-SiC device is thought to be realized by focusing on this type of BPD.