Nucleation and growth of islands on GaAs surfaces

Submonolayer island-size distributions an obtained with scanning tunneling microscopy and used to infer the nucleation and growth kinetics of islands on the three low-index surfaces of GaAs. Comparison with Monte Carlo simulations reveals that on the (110) and (111)A surfaces, random nucleation is followed by the attachment and detachment of single atoms at island edges. But on the (001) surface (using As-4), nucleation is initiated in the trenches of the 2 x 4 reconstruction by pairs of Ga atoms. Growth then proceeds over locally filled trenches, also by the capture of pairs of Ga atoms.