Published in J. Electron. Mater. 27, 308 (1998).
Preparation of atomically flat surfaces on silicon carbide using hydrogen
etching
V. Ramachandran, M. F. Brady, A. R. Smith, and R. M. Feenstra
Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
D. W. Greve
Department of Electrical and Computer Engineering, Carnegie Mellon
University, Pittsburgh, Pennsylvania 15213
Abstract
Hydrogen etching of 6H- and 4H-SiC(0001) surfaces is studied. The as-polished
substrates contain a large number of scratches arising from the polishing
process which are eliminated by hydrogen etching. Etching is carried out
in a flow of hydrogen gas at atmospheric pressure and temperatures around
1600-1700°C attained on a tantalum strip heater. Post-etching atomic
force microscopy (AFM) images show periodic arrays of atomically flat terraces
that are a few thousand Å wide. These terraces are separated by steps
15 Å high in the <1-100> directions. Often, the surface is seen
to be faceted with steps on neighbouring facets forming 60° angles
and offset in the c-direction by half a unit cell. Images of incompletely
etched surfaces show early stages of etching where one can see remnants
of surface damage in the form of arrays of hexagonal pits. On the larger
scale, the surface has a hill-and-valley type morphology. The observed
features are interpreted in a model based on the symmetry of the SiC unit
cell and crystal miscut.
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