Beryllium was ion implanted into GaAs that had been previously amorphized by a liquid‐nitrogen‐temperature arsenic implant. After rapid thermal annealing complete electrical activation of the beryllium was indicated by carrier profiles measured by van der Pauw–Hall and electrochemical capacitance‐voltage techniques. Diffusion of the beryllium profile as determined by secondary‐ion‐mass spectroscopy was suppressed in the arsenic‐preamorphized layer. The combined effects of an amorphous layer to suppress ion channeling and excess arsenic to suppress diffusion resulted in a very abrupt beryllium‐implanted layer. The high electrical activation of the ion‐implanted beryllium represents what we believe is the first successful attempt to activate an impurity implanted into a preamorphized gallium arsenide layer.