A research of composition fluctuations in the solid solutions is conducted in work silicon-germanium with concentration ofunbasic components < 1% and their influence on mobility of current earners. It is shown that effective values of geometrical size of the heterogeneous distributing ofunbasic components are in interval from 20 about 300 Â; temperature dependence of mobility of electrons are well described within the framework of the diffusive approaching in the temperature interval 77-200 K.