It was found that surface migration was effectively enhanced by evaporating Ga or Al atoms onto a clean GaAs surface under an As-free atmosphere or low As pressure. This characteristic was exploited by alternately supplying Ga and/or Al and As to the substrate surface in order to grow atomically-flat GaAs/AlGaAs hetero-interfaces, and also for growing high-quality GaAs and AlGaAs layers at very low temperatures. The migration characteristics of surface adatoms were investigated by using reflection high-energy electron diffraction measurements. It was found that different growth mechanisms operated at high and low temperatures. Both mechanisms were expected to yield flat heterojunction interfaces. By applying this method, GaAs layers and GaAs/AlGaAs single quantum-well structures could be grown at substrate temperatures of 200 and 300C, respectively.

Y.Horikoshi, M.Kawashima, H.Yamaguchi: Japanese Journal of Applied. Physics, 1988, 27[2], 169-79