Transformation of InAs islands to quantum ring structures by metalorganic vapor phase epitaxy

The transformation of InAs islands to quantum rings (QRs) by metalorganic vapor phase epitaxy is investigated. After covering the InAs islands with a thin GaAs partial capping layer and annealing under tertiarybutylarsine (TBAs) flow, ring-shaped nanostructures with a density of 107-109 cm-2 are obtained at 500-600 deg. C. The effects of the growth temperature, annealing process and thickness of the partial capping layer are studied. Optimum values for the annealing time and the partial capping layer thickness were found to be 60-120 s and 0.5-2.0 nm, respectively. Low temperature photoluminescence (PL) emission peaks from islands and QRs grown at 500 deg. C are observed at 1.04 eV and 1.22 eV, respectively. The annealing temperature affected the QR evolution and the PL emission from the QRs due to the temperature dependence of the diffusion rate of indium atoms