Investigation of Factors Influencing the Occurrence of 3C-Inclusions for the Thick Growth of on-Axis C-Face 4H-SiC Epitaxial Layers

In this study, we grew homoepitaxial layers on 3-inch on-axis carbon-face 4H-silicon carbide substrates and attempted to suppress the generation of 3C-inclusions. It was found that the 3C-inclusion density decreased with increasing time spent on reaching an objective flow rate for the precursors. It is suggested that 3C-SiC nucleation occurred on large terraces of the on-axis substrates, which existed before the substrates were covered with spiral hillocks. This nucleation was suppressed owing to the decrease in the degree of supersaturation at the initial growth stage. Moreover, we found that the 3C-inclusions were also generated owing to contamination in the form of graphite products. Furthermore, we succeeded in growing a thick on-axis 4H-SiC homoepitaxial layer on a 3-inch substrate and demonstrating its free-standing epitaxial layer with a thickness of 182 μm and a 3C-inclusion density of 2.0 cm−2.

Influence of Substrate Properties on the Defectivity and Minority Carrier Lifetime in 4H-SiC Homoepitaxial Layers

Two fully loaded epitaxial growth runs with 16 wafers in total were conducted in the AIXTRON G5 WW reactor in order to keep epigrowth conditions constant. The wafers were selected with a large spread of specific resistivity and dislocation densities. The resulting epilayers showed very good intra-wafer homogeneities as well as excellent wafer-to-wafer and run-to-run reproducibility with regard to epilayer thickness and doping concentration, point defect concentrations of Z1/2 and EH6/7 and the resulting Shockley-Read-Hall carrier lifetime. We found that the dislocation densities of the underlying substrates are influencing the stacking fault densities of the epilayers, which then vary between 0.1 and 10 cm-2. A substrate effect on the effective minority carrier lifetime was found.