Atomic-step rearrangement on Si(100) by interaction with arsenic and the implication for GaAs-on-Si epitaxy

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Abstract
The lowest-energy configuration of a class of vicinal Si(100) surfaces has equally spaced steps, each with a height of two atomic units. This results in a single-domain surface with the surface Si-Si dimers being aligned parallel to the step edges. The interaction of As with vicinal Si(100) surfaces is crucial for GaAs growth on Si and there have been several studies of this system, but results from several groups appear to be in contradiction. The results described here, which combine scanning tunneling microscopy, low-energy electron diffraction, and x-ray photoemission, yield a consistent picture of the interaction of As with vicinal Si(100). It is found that depending on the time order of (i) exposure to As and (ii) raising the surface temperature, the directions of the As-As dimers can reproducibly be made perpendicular or parallel to the step edge. In the latter case the step array on the Si substrate is completely rearranged. GaAs grown on one type of dimer arrangement is controllably oriented 90° with respect to that on the other type.