Nanoscale spectroscopic imaging of GaAs-AlGaAs quantum well tube nanowires: correlating luminescence with nanowire size and inner multishell structure

Prete, P.; Wolf, Daniel; Marzo, Fabio; Lovergine, N.

doi:10.1515/nanoph-2019-0156

Cited by 10 publications

(6 citation statements)

References 23 publications

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“…We find similar behaviour for all three QWT thicknesses, even if the thinnest QWT (nominally 1.5 nm) shows the least spatial overlap with the other two energy windows. This is in line with a previous study of GaAs QWTs in AlGaAs barriers using monochromatic CL imaging, showing some fluctuations in the emission energy along the length of NWs with QWTs [31].…”

Section: Side View Cl-imagingsupporting

confidence: 93%

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Cathodoluminescence visualisation of local thickness variations of GaAs/AlGaAs quantum-well tubes on nanowires

et al. 2020

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We present spatially and spectrally resolved emission from nanowires with a thin radial layer of GaAs embedded in AlGaAs barriers, grown radially around taper-free GaAs cores. The GaAs layers are thin enough to show quantization, and are quantum wells. Due to their shape, they are referred to as quantum well tubes (QWTs). We have investigated three different nominal QWT thicknesses: 1.5, 2.0, and 6.0 nm. They all show average emission spectra from the QWT with an energy spread corresponding to a thickness variation of ±30%. We observe no thickness gradient along the length of the nanowires. Individual NWs show a number of peaks, corresponding to different QW thicknesses. Apart from the thinnest QWT, the integrated emission from the QWTs shows homogeneous emission intensity along the NW. The thinnest QWTs show patchy emission patterns due to the incomplete coverage of the QWT. We observe a few NWs with larger diameters. The QWTs in these NWs show spatially resolved variations across the NW. An increase in the local thickness of the QWT at the corners blocks the diffusion of carriers from facet to facet, thereby enabling us to visualise the thickness variations of the radial quantum wells.

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Section: Side View Cl-imagingsupporting

confidence: 93%

“…These studies only reveal the average properties of the QWTs, and spatial resolution is needed to understand how the QWT emission varies along the NW. This has been done with either micro-photoluminescence [9,[28][29][30] (µPL) or cathodoluminescence (CL), using scanning electron microscopy [31] (SEM) or TEM [32].…”

Section: Introductionmentioning

confidence: 99%

Cathodoluminescence visualisation of local thickness variations of GaAs/AlGaAs quantum-well tubes on nanowires

et al. 2020

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“…The nanowire diameter D appears to decrease with increasing their density δ (Table ), an effect driven by the vapor mass-transport controlled overgrowth of (Al)GaAs shells around dense GaAs nanowire arrays . A quantitative model of the effect of precursors vapor mass transport on the nanowire shell growth rates predicts a nonlinear dependence on the actual (i.e., across the sample) value of L δ, initial GaAs nanowire diameters (taken proportional to the Au catalyst NP size D Au ), and deposition times: details of the experimental validation of the shell growth model were provided in refs , . Here, the growth model is employed to best-fit the FE-SEM measured core–shell nanowire average diameters reported in Table to predict the actual thickness of their AlGaAs and GaAs shells in each of the sample areas selected for PR measurements (see below), using the quantity L δ as a free-parameter and the average GaAs core diameters and shell growth times as input figures; best-fitting L δ values for Areas A and B in Table are within a few percent of experimental values.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Optical Absorption of GaAs Near-Band-Edge Transitions in GaAs/AlGaAs Core–Shell Nanowires: Implications for Nanowire Solar Cells

Cretı̀

Prete

Lovergine

et al. 2022

ACS Appl. Nano Mater.

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Dense arrays of core−shell nanowires possess great potential as superabsorptive media for the fabrication of efficient solar cells. We report on GaAs near-band-edge absorption properties of free-standing GaAs− AlGaAs core−shell nanowires having different shell thicknesses, by detailed line-shape analyses of room-temperature photoreflectance (PR) spectra, employing first-derivative Gaussian and Lorentzian models of the GaAs complex dielectric function. Line-shape analyses of the nanowire PR spectra returned a doublet of resonance lines at energies between 1.410 and 1.422 eV, ascribed to strain-split heavy-and light-hole exciton absorption transitions in the GaAs nanowire cores. The optical oscillator strengths of exciton resonances evaluated by Lorentzian analyses of PR features showed a significant enhancement (up to 30×) of GaAs band-edge optical absorption in nanowires with respect to the reference planar structure. Additionally, values of integrated Lorentzian moduli were normalized to the total GaAs core volume fill fraction (estimated in the range 0.5−7.0% with respect to a planar layer of the same height) within each nanowire ensemble, achieving a first ever experimental estimate of the GaAs near band-edge absorption enhancement factor for GaAs−AlGaAs core−shell nanowires in the range 22−190, depending on the nanowire inner core−shell structure. Such strong absorption enhancement is ascribed to improved wave-guiding of incident light into the GaAs cores by the surrounding AlGaAs shell (its average thickness being estimated between ∼14 and 100 nm in the present nanostructures).

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“…To date, the self-catalyzed vapor-liquid-solid (VLS) technique has remained the primary approach for growing the majority of ternary nanowires (NWs). This technique has proven instrumental in enabling the growth of intricate NW structures, including quantum well or core-multishell NWs [16][17][18][19][20]. These advancements pave the way for the expanded utilization of such NWs in electronic and optoelectronic devices.…”

Section: Introductionmentioning

confidence: 99%

The Self-Catalyzed Growth of GaAsSb Nanowires on a Si (111) Substrate Using Molecular-Beam Epitaxy

Zhang

Tang

et al. 2023

Coatings

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GaAsSb semiconductor material, a ternary alloy, has long been recognized as a crucial semiconductor in the near infrared range due to its ability to finely adjust the wavelength through controlling the Sb component. In this work, we report on the pattern of orientation variation in self-catalyzed grown GaAsSb nanowires (NWs). Utilizing solid-source molecular-beam epitaxy (MBE), self-catalyzed GaAs and GaAsSb nanowires (NWs) were grown on Si (111) substrates. The influence of various Sb components on the growth direction of the nanowires in the ternary GaAsSb alloy was examined using scanning electron microscopy (SEM). The inclusion of Sb components was discovered to alter the growth direction of the nanowires, transitioning them from a vertical and inclined orientation to a configuration that encompassed vertical, inclined, and parallel orientations with respect to the Si (111) substrate. As the Sb component in GaAsSb increased, there was an increased likelihood of the nanowires growing parallel to the surface of the Si (111) substrate. A combination of X-ray diffraction (XRD) and Raman spectroscopy validated the presence of Sb components and indicated a high crystalline quality. Additionally, XRD confirmed that the Sb components aligned with the intended structure. These findings establish a solid material foundation for the development of high-performance GaAsSb-based devices.

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Nanoscale spectroscopic imaging of GaAs-AlGaAs quantum well tube nanowires: correlating luminescence with nanowire size and inner multishell structure

Cited by 10 publications

References 23 publications

Cathodoluminescence visualisation of local thickness variations of GaAs/AlGaAs quantum-well tubes on nanowires

Cathodoluminescence visualisation of local thickness variations of GaAs/AlGaAs quantum-well tubes on nanowires

Enhanced Optical Absorption of GaAs Near-Band-Edge Transitions in GaAs/AlGaAs Core–Shell Nanowires: Implications for Nanowire Solar Cells

The Self-Catalyzed Growth of GaAsSb Nanowires on a Si (111) Substrate Using Molecular-Beam Epitaxy

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