High quality AlGaAs/Si layers were obtained by metal organic vapour phase epitaxy using the conformal growth technique. These layers were characterized by means of cathodoluminescence, microRaman, photoluminescence imaging and optical interferometry in the phase stepping mode. The main issues regarding these layers are studied, e.g. Al distribution, quality of the layers, growth front, homogeneity, etc. Special attention was paid to the incorporation of Al. The results herein presented show that an improvement of the quality of AlGaAs/Si heterostructures can be achieved by the conformal growth method.