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Surface Morphologies of 4H-SiC(1120) and (1100) Treated by High-Temperature Gas Etching

The impact of HCl/H2 high-temperature gas-etching on the surface morphologies of 4H-SiC(1120) and (1100) faces is investigated by atomic force microscopy (AFM). Very flat surfaces are obtained on both (1120) and (1100) faces after gas-etching when the substrate surfaces are initially treated by chemical mechanical polishing to remove polishing scratches. The root-mean square roughness values of gas-etched (1120) and (1100) substrates are 0.07 and 0.11 nm, respectively. Within AFM resolution limits no atomic steps are observed on the very flat surfaces of (1120) substrates. On the other hand, clear step-and-terrace structures are observed on (1100) substrates after gas-etching and the height of the steps (2.7 Å) corresponding to the lattice spacing between 4H-SiC(1100) planes (=√3a/2).