Abstract
We have imaged several different vicinal GaAs(001) surfaces, grown by molecular beam epitaxy (MBE), with the scanning tunneling microscope (STM). All the samples were grown under arsenic-rich conditions and had a (2 × 4)/ c(2 × 8) surface reconstruction. The structure of the steps was found to be determined by the structure of the (2 × 4) unit cell. Atomic resolution images of the steps show that there is no step edge reconstruction and that the steps are built up from complete (2 × 4) unit cells. Vicinal GaAs(001) surfaces cut 2° towards (111)A and 2° towards (111)B and grown under step-flow growth conditions were compared. The A-type steps are relatively straight whereas the B-type steps are very ragged. Changing the angle of misorientation of the sample was not found to have a major effect on the step structure. A-type stepped surfaces grown under 2D nucleation growth conditions were found to be less regular than those grown under step-flow growth conditions. The results are discussed in terms of the growth mode of GaAs(001) and the prospects for growing sufficiently regular stepped surfaces for use in device structures such as quantum wires are considered.
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