Abstract
Quantum structures designed using nanowires as a basis are excellent candidates to achieve novel design architectures. Here, triplets of quantum wires (QWRs) that form at the core–shell interface of GaAsP–GaAsP nanowires are reported. Their formation, on only three of the six vertices of the hexagonal nanowire, is governed by the three-fold symmetry of the cubic crystal on the (111) plane. In twinned nanowires, the QWRs are segmented, to alternating vertices, forming quantum dots (QDs). Simulations confirm the possibility of QWR and QD-like behavior from the respective regions. Optical measurements confirm the presence of two different types of quantum emitters in the twinned individual nanowires. The possibility to control the relative formation of QWRs or QDs, and resulting emission wavelengths of the QDs, by controlling the twinning of the nanowire core, opens up new possibilities for designing nanowire devices.
Highlights
Over the past two decades, semiconductor nanowire architectures have been investigated as an alternative to thin films due to advantages, which include a larger active surface area with smaller foot print, lower material consumption, intrinsic formation of an optical cavity, and the ability to tolerate higher levels of strain without dislocation formation.[1−3] Semiconductor nanowires allow the formation of heterostructures in all three directions, namely, along the growth axis and side facets, making them versatile building blocks in the design of complex device structures.[4]
Growth can be considered analogous to growth on nonplanar surfaces in thin film structures, where formation is driven by growth rate anisotropy on different facets, strain, differences in surface diffusion of adatoms, capillary effects arising from shape and entropy of mixing in alloys.[5−7] Composition inhomogeneities may occur for alloy nanowires in the axial direction, due to different diffusion lengths of the different atomic species,[8] and, for nanowires grown by the vapor− liquid−solid (VLS) mechanism, unintentional core−shell structures may form due to different incorporation rates of species during the VLS and simultaneous VS growth mechanisms.[9,10]
In addition to the GaAs quantum well (QW) emission, a number of comparatively sharp, less intense, higher energy lines are observed in the 610−650 nm wavelength range
Summary
Over the past two decades, semiconductor nanowire architectures have been investigated as an alternative to thin films due to advantages, which include a larger active surface area with smaller foot print, lower material consumption, intrinsic formation of an optical cavity, and the ability to tolerate higher levels of strain without dislocation formation.[1−3] Semiconductor nanowires allow the formation of heterostructures in all three directions, namely, along the growth axis and side facets, making them versatile building blocks in the design of complex device structures.[4] The possibility of growth on multiple facets may result in the formation of unintentional features Those that form on the side facets and vertices of nanowires by vapor−solid (VS). Single band effective mass simulations and photoluminescence measurements confirm their respective QWR and QD-like behaviors
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