Epitaxial crystallization of deposited amorphous GaAs layers on GaAs(100) up to the surface by bombardments with 400 keV Ar and 400 keV Kr has been successfully performed at a temperature range between 125 and 200°C. Properties of crystal growth were investigated as a function of ion species (Ar and Kr), energy (400 and 800 keV), ion dose, dose rate and substrate temperature by RBS channeling experiments. The growth rate has shown a nearly linear dependence on ion fluence. Ion bombardments below 100°C have induced further amorphization beyond the initial crystal/amorphous interface. On the scale of nuclear energy deposition density, bombardments with higher electronic excitation efficiency give a small increase of the growth rate. Ar bombardments have shown a strong dependence of the growth rate on dose rate, whereas Kr bombardments have revealed a weak dependence. An apparent activation energy of 0.13 ± 0.06 eV for the crystal growth was observed.