Effects of monolayer coverage, flux ratio, and growth rate on the island density of InAs islands on GaAs

Abstract

We have studied the effects of monolayer coverage, V/III flux ratio and growth rate on the density of three-dimensional growth induced isolated InAs islands grown on GaAs by molecular-beam epitaxy. Within the isolated island growth regime, increasing the monolayer coverage increases the InAs island density with only a small increase in island size. Decreasing the V/III flux ratio or decreasing the growth rate increases the island density without changing the average in-plane island diameter. We have observed island densities that are 80% of the ideal close-packed island density. We propose a model explaining the island density increase with monolayer coverage; local variations in accumulated strain in the wetting layer vary the point at which local islanding is initiated. As more material is deposited more islands are nucleated and the island density increases. The island density increases with decreasing V/III flux ratio or growth rate by increasing the adatom surface diffusion in the underlying wetting layer, leading to a more uniformly strain wetting layer and a more uniformly roughened growth front.