Behavior of Ga atoms deposited on GaAs (111)B and (111)A surfaces

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 19×19 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 As-stabilized 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 2×2 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.