Initial domain structure of GaAs thin films grown on Si(OO1) substrates

The initial domain structure of GaAs films grown on several Si(OO1) surfaces is investigated using X-ray standing waves. GaAs/Si(OOl) samples, 4 ML thick, grown on three different Si substrates were used: an epitaxial Si surface (ESS), a mechanochemically polished surface (MCP), and a mechanochemically polished surface with plasma cleaning (plasma MCP). The domain ratio ambiguousness due to the film thickness is avoided by observing independent Bragg reflections of Si substrates. The results of X-ray standing wave measurement reveal that all daAs films have double domain s&uctures at the initial stage, even though final domain structures are single. The ratio of the two domains was almost 1 : 1 on the MCP surface, 6 : 4 on the ESS surface, and 4.5 : 5.5 on the plasma MCP surface. The dominant GaAs domains on the ESS and plasma MCP surfaces were the same as those obtained on thicker GaAs films. This suggests there is a rapid decrease in the GaAs domain during the early stages of growth on an ESS and plasma MCP surfaces.