A review of molecular-beam epitaxy of GaAs and the observation of surface structures with high-energy electron diffraction in an ultrahigh-vacuum system is described. The utilization of these surface structures as growth conditions to producen- andp-type layers when doped with Sn, Ge, and Mg, and the electrical and optical evaluations of the layers thus grown is also discussed. The molecular-beam epitaxy method may be used to fabricate extremely thin multilayer structures and may play an increasing role in semiconductor technology.