NUCLEATION AND GROWTH OF ISLANDS ON GAAS-SURFACES

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