The electronic properties of the defectE4generated in GaP by 1‐MeV electron irradiation have been studied. The defect exhibits very strong athermal annealing effects undere‐hrecombination conditions. By comparing thermal and optical data evidence is obtained for lattice relaxation when the charge state of theE4defect is changed. A simple configuration coordinate diagram is presented which is in agreement with experimental data and which explains several important features of recombination‐enhanced defects reactions and athermal annealing phenomena.