[en] A review is presented of investigation results of rare-earth doped semiconductors A^IIIB^V by the ESR, photoluminescence, Rutherford scattering methods. Possible positions of rare-earth element atoms in the different semiconductor lattices and their electron structure are discussed. A simple theoretical model of a substitution rare-earth center in binary semiconductors is given. A possible mechanism of f-f transition excitation with participation of the Auger recombination of an electron-hole pair on a connected exciton is considered