Nucleation and Growth of Islands on GaAs Surfaces

Abstract

Submonolayer island-size distributions are 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 ${\mathrm{As}}_{4}$), nucleation is initiated in the trenches of the $2\ifmmode\times\else\texttimes\fi{}4$ reconstruction by pairs of Ga atoms. Growth then proceeds over locally filled trenches, also by the capture of pairs of Ga atoms.