[en] Status of experimental investigations into defect formation in semiconductor related to relaxation of electron excitations is reviewed. The results from impurity-ionization mechanism studies on germanium and indium antimonide are considered in details, as in this case a qualitative comparison of experimental results with those of consistent analytical theory may be carried out. Conditions under which efficiency of this mechanism may be compared to that of elastic displacement mechanism even at above threshold irradiation are determined. Experiments where recombination-heat mechanism of defect transformation is observed are discussed. Information on diffusion-drift annealing of Frenkel pairs that in due conditions may control defect formation, resulting in pair annihilation directly after their production, is presented