A simple experiment involving only the measurement of dark currentIdarkand 1.1 &mgr;m photocurrentIPCin semi‐insulating (SI) GaAs allows an accurate determination of the electron capture cross section &sgr;nfor the important defect EL2 in GaAs. For 45 SI GaAs samples, from 12 different boules, grown by three different techniques, we find thatIPC/Idark=1.96±0.05 at 300 K. This relationship gives &sgr;n=1.4±0.4×10−16cm2, which is compared to previously estimated values. ©1996 American Institute of Physics.