The effect of initial low-temperature grown buffer (LT buffer) layer thickness on quality of InSb grown on GaAs substrate by molecular beam epitaxy (MBE) with the two-step growth method was investigated. The characteristics of InSb layers were analyzed by using Raman scattering, triple-axis crystal X-ray diffraction (XRD) and atomic force microscopy (AFM). It is shown that the crystalline quality and the root-mean-square (RMS) roughness of the InSb layer have close relation to the thickness of initial grown low-temperature buffer layer. With the spatial correlation model, the Raman line shapes of the first-order longitudinal optical phonon mode of InSb epilayer have been analyzed, which well agrees with the experimental results. We found that the optimal LT buffer thickness is about 30 run suitable for obtaining smooth surface and high-quality InSb epilayer grown on semi-insulated GaAs substrate. (c) 2005 Elsevier B.V. All rights reserved.