Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-innanowire system that reproducibly self-assembles in core–shell GaAs/AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solid-state lighting devices and third-generation solar cells.
M. Heiss, Y. Fontan, A. Gustafsson, G. Wüst, C. Magen, D. D. O’Regan, J.W. Luo,B. Ketterer, S. Conesa-Boj, A. V. Kuhlmann, J. Houel E. Russo-Averchi, J. R. Morante,M. Cantoni, N. Marzari, J. Arbiol, A. Zunger, R. J.Warburton and A. Fontcuberta Morral" Self-assembled quantum dots in a nanowire system for quantum photonics" Nature Materials 12, 439 (2013) .(PDF)