We have achieved the first successful growth of GaAs films with good electrical properties at substrate temperatures below 480 °C. The electrical and photoluminescence properties of films grown atTs≊380 and 450 °C have been dramatically improved by reducing the growth rate significantly below the usual rate of ∼1 μm/h. Reductions in the growth rate can be expected to improve the quality of MBE films by allowing sufficient time for Ga and As adatoms to jump to equilibrium lattice positions before they are incorporated into the growing crystal by interacting with other adatoms. We further observed that the density of a major morphological defect of MBE GaAs films—the oval defect—was strongly correlated with the growth rate. The density of such defects was ∼500 cm−2for films grown at ∼0.02 μm/h.