Buffer layers of GaAs1-xSbx were grown on an InP substrate starting at x=0.49 (lattice matched to InP) and increasing x in steps of 0.03-1.0 (GaSb), followed by a 0.5 mu m thick GaSb metamorphic layer. A 10 nm thick InAs quantum well was grown on top and capped with a 100 nm GaSb. All layers were grown using gas source molecular beam epitaxy by reducing the As flux in small steps while keeping the Sb flux fixed. The substrate temperature during growth was similar to 490 degrees C. High-Resolution x-ray diffraction analysis showed that the metamorphic layer was almost fully relaxed. Cross-sectional transmission electron microscopy images show that a postgrowth anneal at 600 degrees C for 30 s successfully reduces the number of dislocations threading through the metamorphic layer. Hence the top layer can be used satisfactorily as a pseudosubstrate for subsequent layer growths assuming a GaSb lattice constant. (c) 2006 American Vacuum Society.