In0.2Ga0.8As layers were grown on GaAs Substrates with graded buffer layers h metalorganic vapor phase epitaxy at 370-630 degrees C. Good surface morphology with a crosshatch pattern (0 1 P) was, is obtained at 000 and 630 C, Transmission electron microscopy (TEM) observation confirmed that the cap layers had a threading dislocation density of between 1.3 and 2.0 x 106 cm (2). At 500 C. a layer showed a rough surface morphology, Phase separation vas revealed by TEM. The threading dislocation density was over I x 10(7) cm(2) at 500 C. Good surface morphology with it CHP was obtained at 430, 450 and 480 C. A layer grown at 430 C showed the lowest threading dislocation density of 2,5 X 10(5)cm (2). Low temperature growth was effective for lowering the threading dislocation density in the cap layers. (c) 2005 Elsevier B.V. All rights reserved.