Recently, the accuracy and reliability of the accepted (0/+) donor energy level E-D of the defect EL2 in GaAs, especially as measured by temperature-dependent Hall-concentration measurements (Arrhenius plot), have been questioned. Here we show that the accepted Hall-effect value, E-C=0.75 eV, is accurate and reliable; however, it must be remembered that an Arrhenius plot effectively gives E-D at T=0, whereas experiments such as photoluminescence, photocapacitance, and photoconductivity, which rely on a peak or threshold, give E-D at a particular temperature T. For comparative purposes, we suggest the relationship E-D(T)=(0.75-2.2 x 10(-4)T) eV. (C) 1999 Elsevier Science Ltd. All rights reserved.