Composition and morphology of SiGe alloys grown on Si(100) using an Sb surfactant

The effect of using a surfactant during SiGe alloy growth was investigated. Previous studies of surfactant-assisted growth have focused on the properties of pure Ge films grown on Si or on pure Si grown after Ge. Using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM), we have studied the Ge compositional profile and morphology of SiGe alloys grown by molecular-beam epitaxy on Si (1 0 0) with an Sb surfactant. Using XPS, we have found that Ge segregation occurs at the start of alloy growth in the presence of up to 1 monolayer (ML) of Sb surface coverage but that the amount of Ge segregation is less than without Sb. We did find, however. that 0.75 ML of Sb after alloy growth can completely suppresses Ge segregation into a subsequent Si capping layer. Using XRD and TEM, we have found that SiGe films grown with 0.8 ML of Sb did not relax appreciably but did produce a non-planar surface morphology having an abrupt chemical interface between the alloy layer and the capping layer. We also found that the use of 0.8 ML of Sb resulted in compositional fluctuations within the alloy. We propose that the use of the Sb surfactant resulted in a separation of Si and Ge during the growth of the alloy layer producing the observed Ge segregation, surface morphology and compositional fluctuations. (C) 2000 Elsevier Science B.V. All rights reserved.