Lateral variations in self-assembled InGaAs quantum dot distributions

The lateral uniformity of self-assembled InGaAs quantum dots grown by molecular beam epitaxy (MBE) was assessed as a function of growth conditions. Variations in the dot density and height were determined from atomic force micrographs. Growth rate had a large influence on lateral uniformity. The most uniform dot distributions were grown at low rates, 0.15 monolayers/s (ML/s). Dots deposited at a rate of 1.15 ML/s had large variations in both height and density. These variations decreased as the dot density increased; however, they remained larger than those of dots deposited slowly. The lateral uniformity of dots deposited quickly also improved for the top layer of dots in stacked layers, even though these layers had decreased dot densities. There were negligible differences in the lateral height and density uniformities of dots as functions of continuous versus pulsed growth, wafer diameter and mole fraction of In.