Comprehensive studies on the surface morphological evolution of AlInSb metamorphic buffers and InSb QWs grown on top were conducted as a function of the GaAs (001) substrate offcut angles. We confirmed our earlier postulation that the vicinal surfaces defined by the hillock facets have the exact surface orientation needed to achieve large-area hillock-free surfaces. The related morphological transitions were discussed with a graphic illustration. The optimum substrate offcut for InSb towards [(1) over bar 10] direction was found to be around 0.5-0.6 degrees with our growth conditions. On 2-inch GaAs (001) substrates with this offcut, a hillock-free and atomically smooth surface morphology was successfully achieved for modulation-doped InSb QWs.