Surfactant-mediated growth of Si1-xSnx layers by molecular-beam epitaxy

Submonolayers of Bi were used as surfactant in the growth of Si1-xSnx (0.01 less than or equal to x less than or equal to 0.04) layers on Si(001) and relaxed Si-Ge substrates. The Si1-xSnx layers were investigated using Rutherford backscattering spectrometry, atomic force microscopy, transmission electron microscopy and preferential-etching experiments. The investigation of surfactant-mediated growth of epitaxial Si1-xSnx was motivated by a possible use of relatively higher growth temperatures without relaxation by surface precipitation. It is demonstrated that higher growth temperatures are attainable when Bi is used as surfactant if the surface-segregated Sn layer is relatively small, equivalent to Si1-xSnx layers of low strain. The increase in growth temperature leads to a significant improvement in the crystalline quality of these Si1-xSnx layers.