Growth of highly ordered relaxed InAs/GaAs quantum dots on non-lithographically patterned substrates by molecular beam epitaxy

Highly ordered arrays of InAs quantum dots are grown on GaAs (1 0 0) substrates that have been patterned non-lithographically using self-organized anodized aluminum oxide membranes as an etching mask. The process and benefit of pre-coating the substrate with a protective SiO2 film are explained in terms of preserving topographic contrast between the etched and unetched regions. The influence of the growth parameters (growth time, InAs rate, and substrate temperature) are determined. In particular, we find that decreased growth temperature enhances the pattern-driven growth mechanism and increases selectivity. Growths with different InAs exposure time reveal the nanopore filling process and a self-limiting dot size. Analysis of high-resolution transmission electron microscopy images suggests that the dots consist of completely relaxed InxGa1−x  As with x=0.92x=0.92.