Surface Segregation at Boron Planar Doping in Silicon Molecular Beam Epitaxy

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Abstract
When a 1.0 monolayer coverage of boron atoms was evaporated on a Si(100) clean surface, followed by a 200 Å n--type Si epitaxial layer, about 70% of the boron atoms were activated. However, using Auger analyses, it was found that surface boron segregation occurred during this process and the boron profile was smeared. In the case of Si(100) substrate, boron atoms were incorporated into the growing Si film in proportion to the surface boron density. On Si(111), surface boron atoms did not incorporate in proportion to the surface boron density and boron segregation had a large growth temperature dependence. This difference is explained using the existence of a √3×√3R30° surface superstructure of boron only on the Si(111) surface.