Formation of a single In(Ga)As/GaAs quantum dot embedded in a site-controlled GaAs nanowire by metalorganic chemical vap
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Formation of a single In(Ga)As/GaAs quantum dot embedded in a site-controlled GaAs nanowire by metalorganic chemical vapor deposition for application to single photon sources J. Tatebayashi1, Y. Ota1, D. Karunathillake,1,2 S. Ishida1,2, M. Nishioka1,2, S. Iwamoto1,2 and Y. Arakawa1,2 2
1 NanoQUINE, Univ. of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505, JAPAN Institute of Industrial Science, Univ. of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505, JAPAN
ABSTRACT We report the formation and optical properties of site-controlled InAs/GaAs quantum dots (QDs) embedded in GaAs nanowires (NWs) by selective metalorganic chemical vapor deposition for application to single photon sources. InAs/GaAs QD-in-NWs with various InAs thicknesses are realized on patterned GaAs(111)B substrates in the form of InAs/GaAs heterostructures and identified by structural analyses using scanning transmission electron microscopy and photoluminescence characterization. Sharp excitonic emission peaks at 10 K from single QD-in-NWs with the narrowest exciton linewidth of 87 μeV are observed. Light emission from the single QD-in-NW shows photon antibunching which evidences single photon emission from high-quality QD-in-NWs. INTRODUCTION Development of non-classical light generators utilizing the discrete density of states of quantum dots (QDs)[1] with high light-extraction efficiency has long been recognized as a major challenge in the context of quantum communication to enhance photon out-coupling to external optics. Many groups have demonstrated the enhancement of the light-collection efficiency from single photon sources in photonic nanowires (NWs) with carefully tailored end by applying a “top-down” approach using electron-beam (EB) lithography and reactive ion etching (RIE)[2,3]. Recently, formation of QD-in-NWs utilizing a “bottom-up” approach has been exploited as a promising candidate for such applications because of improved quality of surface morphology which is damaged by the top-down approach. Furthermore, the growth of QD-in-NWs on (111)oriented substrates has attracted scientific attention for applications in entangled-photon emitters because fine-structure splittings induced by piezoelectricity, interface and strain asymmetries can be eliminated due to the threefold rotational symmetry of the (111) plane[4,5]. In addition, strain-free QDs would be obtainable in the growth of QD-in-NWs due to strain relaxation via lateral direction between lattice mismatched materials[6,7], which would enable the realization of ultra-high-efficiency intermediate-band solar-cells (IBSCs) utilizing densely-packed, multistack QDs[8]. In the formation of QD-in-NWs, there are predominantly two bottom-up approaches: the vapor-liquid-solid (VLS) method [9] and the “site-controlled”, catalyst-free method using selective growth[10]. For high-performance NW-based optoelectronic devices, it is crucial to design and realize site-controlled QD-in-NWs in terms of size uniformity, position/orientation controllability, reproducibility and crystal quality due t
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