Investigation on Step-Bunched Homoepitaxial Layers Grown on On-Axis 4H-SiC Substrates via Molten KOH Etching

Wafer-scale on-axis 4H-SiC epitaxial layers with very low roughness were obtained in this study. By performing carbon-rich hydrogen etching and epitaxial growth of the epitaxial layer at different temperatures, local mirror regions (LMRs) with root mean square (RMS) roughness less than 0.2 nm were obtained on the epitaxial layer surface. The LMRs' length is tens of millimeters, and the width is sub-millimeters. The step-flow growth induced by threading screw dislocations (TSDs) was observed on the epitaxial layer surface by atomic force microscopy (AFM), together with the double bi-atomic step-flow growth induced by the step bunch, which was the cause of LMRs. Furthermore, the growth mechanism was investigated by wet etching. The etching pits were found to be associated with 3C-SiC and their effect on the growth rate of epitaxial layers was further explored.