Conversion of Shockley partial dislocation pairs from unexpandable to expandable combinations after epitaxial growth of 4H-SiC

Abstract

Conversion of Shockley partial dislocation pairs from unexpandable to expandable combinations has been considered possible during epitaxial growth. The step-flow model was proposed to explain the conversion, in which an unexpandable 30° C-core partial dislocation in the substrate changes into an expandable 30° Si-core partial dislocation in the epitaxial grown layer. We observed this conversion experimentally by a transmission electron microscope and confirmed the core-species change by high-angle annular dark-field scanning transmission electron microscopy. In addition, other unexpandable combinations of partial dislocations were examined for the possibility of converting to expandable. As a result, the unexpandable basal plane dislocations with a Burgers vector of ±(1/3)[112¯0] in the substrate were confirmed to be a necessary condition for forming expandable 30° Si-core partial dislocations after epitaxial growth that could expand single Shockley-type stacking faults and degrade reliability of 4H-SiC power devices.