Using a classical photocapacitance technique, we have transformed the well-known EL2 defects, related to the As antisite in GaAs, into their metastable states. Using the capacitance, we have monitored the temperature dependence of the electron occupancy of these metastable states at thermal equilibrium. From this study, we deduce that a level located at 40 meV below the conduction band is associated with electron ionization from the metastable EL2 states. ©1997 American Institute of Physics.