Multilayer structures of low-temperature-grown GaAs(LT-GaAs) into which ultra-thin layers containing excess As are periodically introduced are grown by molecular beam epitaxy. The concentration of excess As in the ultra-thin layers is determined by the analysis of the intensity of a satellite reflection of the multilayer structure along with a peak shift of the 400 Bragg reflection from that of the GaAs substrate. The analysis shows that the concentration of excess As in the ultra-thin layers is significantly higher than those of thick LT-GaAs layers grown under the identical condition of the fluxes and the substrate temperature. (C) 2002 Elsevier Science B.V. All rights reserved.