Local etching of nanoholes and quantum rings with InxGa1-x droplets

We study the formation of nanoholes and quantum rings in GaAs and AlGaAs surfaces by local droplet etching with InxGa1-x. The rings are crystallized from droplet material and surround the nanohole openings. In particular, the influence of the In content x on density, diameter, and depth of the nanoholes is investigated. Our data establish an exponential dependence of these quantities on x, which is quantitatively reproduced by a model that considers different surface diffusion energy barriers for Ga and In. By etching with pure In, hole densities as low as 5 x 10(6) cm(-2) have been achieved. In addition, for low In content incompletely removed initial droplets are visible on the surface. These droplets are not visible on samples with x > 0.5 which indicates a higher desorption rate of In compared to Ga. As a consequence, even in the case of etching with InGa the quantum rings consist of nearly pure GaAs. This is confirmed by photoluminescence experiments of quantum rings overgrown with AlGaAs barrier material. (C) 2009 American Institute of Physics. [doi:10.1063/1.3225759]