INITIAL DOMAIN-STRUCTURE OF GAAS THIN-FILMS GROWN ON SI(001) SUBSTRATES

The initial domain structure of GaAs films grown on several Si(001) su rfaces is investigated using X-ray standing waves. GaAs/Si(001) sample s, 4 ML thick, grown on three different Si substrates were used: an ep itaxial 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 avoi ded by observing independent Bragg reflections of Si substrates. The r esults of X-ray standing wave measurement reveal that all GaAs films h ave double domain structures at the initial stage, even though final d omain 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 plas ma MCP surface. The dominant GaAs domains on the ESS and plasma MCP su rfaces were the same as those obtained on thicker GaAs films. This sug gests there is a rapid decrease in the GaAs domain during the early st ages of growth on an ESS and plasma MCP surfaces.