Configuration coordinate diagram for the E4 defect in electron-irradiated GaP

The electronic properties of the defect E4 generated in GaP by 1-MeV electron irradiation have been studied. The defect exhibits very strong athermal annealing effects under e-h recombination conditions. By comparing thermal and optical data evidence is obtained for lattice relaxation when the charge state of the E4 defect 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.