Conductivity and Hall effect measurements have been performed on 2 μm thick molecular beam epitaxial layers grown at very low substrate temperatures, 200 to 400°C. For growth temperatures below 300°C, the conduction is dominated by hopping between arsenic antisite defects of concentrations up to 1020 cm−3. Below measurement temperatures of about 130 K, the hopping conduction can be quenched by strong IR light illumination, because the antisite then becomes metastable. The antisite has a thermal activation energy of , and thus is not identical to the famous EL2. Both nearest‐neighbor and variable‐range hopping mechanisms are considered in the analysis.