Effects of stress on the evolution of Σ-shaped dislocation arrays in a 4H-SiC epitaxial layer

Abstract

Five Σ-shaped dislocation arrays in 100-mm-diameter, 12-μm-thick 4H-SiC epitaxial wafers were observed using photoluminescence mapping. The structure of the Σ-shaped dislocation arrays was characterized using nondestructive analytical techniques of photoluminescence mapping, microphotoluminescence spectroscopy, and x-ray topography. Each Σ-shaped dislocation array consists of two basal plane dislocations (BPDs) at the interfacial dislocation terminal points and two half-loop arrays. The interfacial dislocation pairs nucleate from BPDs in the substrate. Three independent stresses lead to interfacial dislocations: thermal stress (τT), stress induced by misfit strain (τM), and interaction force (τI). The main cause of interfacial dislocation formation is attributed to the development of τT within the wafer due to temperature nonuniformity. τM and τI also contribute to the formation of interfacial dislocations. Larger stresses increase the BPD glide velocity in the interfacial dislocations, thereby producing longer Σ-shaped dislocation arrays.