Up to 500 nm thick crack-free Al0.25Ga0.75N and Al0.32Ga0.68N epilayers have been grown on Si (111) substrates. The surface morphology of samples was investigated by an optical microscope and a scanning electron microscope (SEM). Pits and shale-like surface structure have been observed. XRD rocking curve measurements indicate the crystal quality of samples. The analyses show that the Al source flux is an important factor in growing AlGaN on Si (111). The information from the Micro-Raman spectra supported that Al atoms are gathered at nearby areas of the pits originated from the AlN/Si (111) interface in the initial stage of AlGaN growth. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.