We present a virtual substrate for high quality InAs epitaxial layer, obtained via metalorganic vapor-phase epitaxy growth of Sb-assisted InxGa1-xAs metamorphic buffers, following a convex compositional continuous gradient of the In content from x = 53 % to 100 %. The use of Trimethylantimony (or its decomposition products) as a surfactant was found to be a suitable way to control defect formation during the relaxation process. Reliably uniform growth with good morphology was obtained on crystals with misorientation toward [111]B direction.