EN
The paper shows an influence of doping on lattice constant of a semiconductor. Three effects are discussed: (i) "size" effect caused by a different ionic radii of dopant and host atoms, (ii) lattice expansion by free electrons proportionally to the deformation potential of the conduction-band minimum occupied by this charge, (iii) different thermal expansion of the undoped and doped samples. The experiments have been performed by using the high resolution X-ray diffraction at 77-770 K on AlGaAs:Te and GaAs:Si.