Polytype Stability and Microstructural Characterization of Silicon Carbide Epitaxial Films Grown on [ $$ {\hbox{11}}\overline{{\hbox{2}}} {\hbox{0}} $$ ]- and [0001]-Oriented Silicon Carbide Substrates

Abstract

The polytype and surface and defect microstructure of epitaxial layers grown on 4H( $$ {\hbox{11}}\overline{{\hbox{2}}} {\hbox{0}} $$ ), 4H(0001) on-axis, 4H(0001) 8° off-axis, and 6H(0001) on-axis substrates have been investigated. High-resolution x-ray diffraction (XRD) revealed the epitaxial layers on 4H( $$ {\hbox{11}}\overline{{\hbox{2}}} {\hbox{0}} $$ ) and 4H(0001) 8° off-axis to have the 4H-SiC (silicon carbide) polytype, while the 3C-SiC polytype was identified for epitaxial layers on 4H(0001) and 6H(0001) on-axis substrates. Cathodoluminescence (CL), Raman spectroscopy, and transmission electron microscopy (TEM) confirmed these results. The epitaxial surface of 4H( $$ {\hbox{11}}\overline{{\hbox{2}}} {\hbox{0}} $$ ) films was specular with a roughness of 0.16-nm root-mean-square (RMS), in contrast to the surfaces of the other epitaxial layer-substrate orientations, which contained curvilinear boundaries, growth pits (∼3 × 104 cm−2), triangular defects >100 μm, and significant step bunching. Molten KOH etching revealed large defect densities within 4H( $$ {\hbox{11}}\overline{{\hbox{2}}} {\hbox{0}} $$ ) films that decreased with film thickness to ∼106 cm−2 at 2.5 μm, while cross-sectional TEM studies showed areas free of defects and an indistinguishable film-substrate interface for 4H( $$ {\hbox{11}}\overline{{\hbox{2}}} {\hbox{0}} $$ ) epitaxial layers.