Internal architecture and multiple structural transformations of large-height stacking faults in 4H-SiC trapezoidal defects

4H-SiC is a critical compound semiconductor for high-power electronic devices. However, the performance of 4H-SiC substrates and epitaxial wafers is often compromised by structural defects, predominantly stacking faults (SFs). Trapezoidal defects (TZDs)—bar-shaped SFs exceeding 1000 µm in length—are prevalent in these materials. Although achieving defect-free 4H-SiC is crucial, the fundamental crystallographic nature of TZDs remains largely elusive. In this study, we demonstrate that TZDs are not single SFs but comprise multiple Shockley-type large-height SFs (LHSFs) of up to 32 layers. These form through successive structural transformations between SFs via the gliding of basal plane Shockley partial dislocations (BPSPDs). These mechanisms were comprehensively confirmed using photoluminescence (PL) mapping, KOH etching, X-ray topography, and high-angle annular dark-field high-resolution scanning transmission electron microscopy (HAADF HR-STEM). Our findings reveal that the stacking fault energies of almost all LHSFs are exceptionally low (< 1 mJ/m²), elucidating the thermodynamic driving force for their facile and multiple transformations. Furthermore, we successfully identified the previously indeterminate PL emission wavelengths for various LHSFs, narrowing their signatures to a precise 425–431 nm range based on their specific fractional configurations. Crucially, we highlight the severe risk of defect misidentification; relying solely on these optical signatures can lead to erroneous conclusions, as starkly demonstrated by a Shockley-type LHSF emitting at 457 nm—perfectly mimicking a Frank-type defect. Ultimately, this study provides a fundamental understanding of atypical yet pervasive Shockley-type LHSFs, which is essential for advancing the physical understanding of defect evolution and crystallographic stability in wide-bandgap semiconductors.