For a set of p-GaN films and p-AlGaN/GaN modulation doped superlattices hole mobilities were measured together with atomic force microscope (AFM) imaging of the surface. It is shown that the apparent mobilities are strongly affected by the parameters of the mosaic structure of the films. Multifractal analysis (MFA) of the AFM images is shown to be a very useful instrument for quantitative comparison of various mosaic structures and for identifying the structures with low mobilities. A good correlation between such MFA parameters as the Renyi dimension and the order index degree and the measured mobilities is reported. (C) 2003 Elsevier Science Ltd. All rights reserved.