We investigate the behavior of Ga atoms deposited on GaAs (111)B and (111)A surfaces by the intensity measurement of the specular spot of the reflection high-energy electron diffraction. Characteristics of these two surfaces are very different. For (111)B surface, we reveal that the deposited Ga atoms fill the Ga vacancy of root 19 x root 19 reconstruction until the surface is fully covered by one mono-layer of Ga. Excess atoms deposited on the fully covered surface form droplets and act as a Ga source during the recovery process. The surface recovers initial condition by supplying As. Alternate formation of Asstabilized and Ga-stabilized surfaces controlled by growth sequence enables the migration-enhanced epitaxy on the GaAs (111)B surface. For (111)A surface, in contrast, the stable surface is 2 x 2 reconstruction even under As irradiation. Deposition of Ga only forms droplets on the surface. The MEE mode growth is not suitable on this surface since As-stabilized surface is hard to form. (C) 2017 Elsevier B.V. All rights reserved.