Due to the elastic interaction of point defects created by external irradiation, the homogeneous distribution of defects is shown to become unstable at defect concentration larger than certain threshold value and the superlattice of defect density appears in the crystal. The parameters of the superlattice are determined by kinetic characteristics of the system (diffusion coefficient, lifetime of defects, and so on). The created superlattice is an example of the dissipative structure that exists far from equilibrium. The condition of development, the stability, the main parameters of superlattice are analyzed for three cases when a crystal contains (1) vacancies, (2) vacancies and interstitials, and (3) vacancies, interstitials and traps for defects. The calculations show that for realistic parameters of crystals and realistic conditions of irradiation the most preferable conditions for the creation of superlattice occur in the third case.