Control of nano-scale quantum wire structures and optocal properties of one-dimensional excitons

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(1) Invesrigation of growth mechanism and shape control of the ridge quantum wireWe connected an ulfra high vacuum atomic force microscope to the molecular beam epitaxy system and realized an in-situ observation of the formation process of ridge quantum wire. Ridge quantum wire takes form throuhg the following process. First, (001)-(111) B facet structures appear on the mesa shaped substrate. On the border of (001)-(111) B facet, (101) surface and (112) surface also appear. As these surfaces grow, (001) surface disappears. Since Ga atoms bury vicinal facets, very smooth ridge strudture is formed. We made a successful growth of 10nm scale ridge quantum wire under the substrate temperature less than 520ﾟC.(2) Optical properties of one-dimensional exciton in the nm-scale quantum wireWe fabricated the T-shaped GaAs quantum wire by the cleaved-edge over-growth and measured spatially resolved micro photo luminescence in the magnetic fields. It was clarified that in the T-shaped quantum wire with 5nm-thick AlAs barriers the lateral confinementenergy was 38 meV and that the binding energy of one-dimentional exciton increased up to 27meV.We investigated the anisotropy of valence band from the optical anisotropy which was in good agreement with the theory. From the diamagnetic shifts, we successfully observed the dependence of the spatial extent of wave function on the width of quantum wire. It was also found that oscillator strength increased as lateral confinement was effective from the photo luminescence excitation experiment.