Synchrotron X-Ray Topography Analysis of Low Angle Grain Boundaries Induced by Growth Step Flow in PVT-Grown 4H-SiC Crystals

Synchrotron X-ray topography (XRT) combined with ray-tracing simulation was employed to examine the distribution and formation mechanisms of LAGBs in off-axis 4H-SiC wafers grown by PVT. TED-LAGB networks were observed adjacent to the facet, along with three TED-LAGBs emanating from micropipes on the left edge of the wafer. Ray-tracing simulations enabled the identification of TED Burgers vectors by correlating simulated and observed contrast configurations. The results suggest that large TED-LAGB networks near facets originate from misorientations between growth fronts of horseshoe-shaped steps incorporating prismatic slip dislocations, induced by radial temperature gradients. Similarly, LAGBs associated with micropipes arise from localized step-flow perturbations. These findings provide a revised mechanism for TED-LAGBs formation, establishing a link between their spatial distribution and growth dynamics, and offering new insights into their role in determining the quality of 4H-SiC substrates.