We have investigated the structural properties of AlGaSb films grown on Si (100) substrates with multi-buffer layers (GaSb/AlSb/GaSb) inserting a thin AlSb and InSb quantum dots (QDs) inter-buffer layer. Atomic force microscopy measurements of the buffer layers with the QDs inter-buffer layer showed the mirror-like surface with a low defect density. Also, the surface roughness of a resulting AlGaSb film on the buffer layers with the QDs inter-buffer layer is decreased by a factor of about 10 compared with the roughness of the film without the QDs interlayer. In addition, X-ray diffraction rocking curve result showed that the structural properties of AlGaSb layer with the QDs interlayer were improved significantly. We suggest that the significant reduction of the dislocation density in the AlGaSb film was due to the dislocations being prevented from propagating into the AlGaSb overlayer by the thin AlSb and InSb QDs interlayer. (C) 2011 Elsevier B.V. All rights reserved.