Si‐doped GaAs layers were grown by the migration‐enhanced epitaxy (MEE) method and by the conventional molecular‐beam epitaxy (MBE) method, for the substrate temperatures between 220 and 670 °C. For the layers grown below 400 °C, the Si activation and mobility of the MEE layers are significantly higher than those of the MBE layers. For substrate temperatures above 400 °C, the MEE and MBE layers have roughly similar Si activation and mobility. The Raman and 4‐K photoluminescence spectra of the layers are consistent with the measured electron concentrations. This work suggests that for Si doping in GaAs at low substrate temperatures (below 400 °C), the MEE method is a very desirable alternative to the conventional MBE method.