Effects of very low growth rates on GaAs grown by molecular beam epitaxy at low substrate temperatures

Molecular beam epitaxy of GaAs is conventionally performed at growth rates of ∼1 μm/h. For growth rates in this range, donor-doped films grown at substrate temperatures below 500 °C have low carrier concentrations and high resistivities. We have grown Si-doped films with good electrical properties at substrate temperatures of 380 and 450 °C by reducing the growth rates to ∼0.02 and 0.2 μm/h, respectively. We believe that the improvement can be attributed to a reduction in the concentration of crystal defects, which occurs because the Ga and As atoms adsorbed on the substrate surface have sufficient time to reach appropriate lattice sites before they are incorporated into the growing film.