Quantum rings formed in InAs QDs annealing process

InAs quantum dots (QDs) were grown by molecular beam epitaxy in the Stranski-Krastanow growth mode. The samples were placed between two undoped GaAs slices and annealed in nitrogen ambient at different temperature. Effect of annealing temperature on the evolution of QDs morphology is investigated by the AFM. This behavior can be attributed to the mechanisms of QDs ripening, intermixing and segregation in the annealing process. A number of QDs have evoluted into the uniform distribution quantum rings (QRs) when the sample was annealed at the temperature of 800 °C. The results indicated that high density and uniform QRs can be obtained by the post-growth technique.