GaAs layers were grown by MBE on (6 3 1)-oriented substrates under a variety of growth conditions. The structural properties of the samples were studied by atomic force microscopy and micro-Raman spectroscopy. Hillock structures were formed on the layers surface presenting an elongation towards the [(5) over bar, 9, 3] direction, with dimensions and density that depend on the growth conditions. Raman spectra from the samples showed two peaks corresponding to transversal (TO)- and longitudinal (LO) optical phonons. According to the calculated dipole selection rules both TO and LO phonons are allowed for backscattering from a perfect GaAs(6 3 1) surface, but with the intensity of the TO phonon much larger than that of the LO phonon. This result was used to study the changes in the GaAs surface morphology as a function of growth time and growth temperature. By employing a relatively high growth temperature and a high As pressure a surface corrugation was formed which could be used for the synthesis of one-dimensional structures. (c) 2006 Published by Elsevier B.V.