The second energy level of the EL2 defect (EL2+/++) is observed by using the infrared absorption technique and monochromatic light irradiation in undoped and lightly alloyed unannealed bulk GaAs. The EL2+/++spectrum exhibits a complex structure and it does not exist in annealed samples. The EL2+/++→EL20/+and EL20/+→EL2+/++transitions were obtained by illuminating the samples with 0.7≤h&ngr;≤0.95 eV and 1.3≤h&ngr;≤1.5 eV, respectively. The transformation EL2+/++↔EL20/+can be achieved in less than 10 s and can be repeatedly switched back and forth between the two states.