Origin of energy dispersion in AlxGa1−xNÕGaN nanowire quantum discs with low Al content

Individual GaN nanowires containing AlxGa1−xN/GaN quantum discs QDiscs with Al content x16% have been investigated by microphotoluminescence, transmission electron microscopy, and theoretical modeling. Single quantum discs show narrow emission lines with a linewidth as low as 3 meV at energies above the GaN band gap while the emission of nanowires containing multiple quantum discs shows multiple peaks with total spectral broadening that depends on the Al content in the barrier. As assessed by simulations of the quantum confinement based on a three-dimensional effective-mass model, the main factors influencing the spectral dispersion are: i strain relaxation in the QDiscs, strongly affected by the presence of a lateral AlGaN shell with a progressively changing thickness formed during the barrier growth; ii monolayer fluctuations in the QDisc thickness