Direct evaluation of threading dislocations in 4H-SiC through large-angle convergent beam electron diffraction

Abstract

ABSTRACTIn this study, the structures of threading dislocations (TDs) in a 4H-SiC epilayer were directly characterised using large-angle convergent beam electron diffraction (LACBED) via transmission electron microscopy (TEM), by examining the splitting of reflections due to the presence of dislocation lines. Previously, X-ray topography (XRT) mapping in combination with ray-tracing simulations has been shown to be an efficient method for imaging and differentiating common TD types and variants in 4H-SiC. In this work, the validity of XRT-based results was verified by LACBED through direct evaluation and differentiation of the Burgers vectors and physical crystallographic features of all threading edge, threading screw, and threading mixed dislocations variants. The LACBED results agreed with the XRT-based results with respect to TD type and variant. The screw-sense or half-plane orientation and Burgers vector determined from LACBED analysis for each TD were self-consistent. For the case of -TEDs, atomic-resolution analysis of the core structure, through high-angle annular dark field scanning TEM, directly revealed two half-planes, each with a Burgers vector component, and the sum of these components was confirmed to be . Finally, an algorithm for efficient LACBED analysis of TDs in 4H-SiC was discussed.