The thermal interactions of thin AlGe and AlNiGe layers with a bulk GaAs monocrystal were investigated. The heat treatment of these systems was carried out in the working chamber of a scanning electron microscope. The SEM pictures were analysed using a fractal mathematical technique. It was found that the surface of the samples has fractal character. No temperature dependence of the fractal dimension was observed. The samples were also studied using the structural entropy versus filling factor maps of the samples in order to find their localization properties. The SEM pictures of AlGe perform mostly as a Gaussian functions, whereas the AlNiGe samples show usually a behaviour with exponential decay. © 2009 Elsevier Ltd. All rights reserved.