Nanometer-scale sharpness in corner-overgrown heterostructures

Steinke, Lucia; Cantwell, Patrick R.; Zakharov, D.N.; Stach, E.A.; Zaluzec, N. J.; Morral, Anna Fontcuberta i; Bichler, Max; Abstreiter, G.; Grayson, M.

doi:10.1063/1.2988526

Cited by 10 publications

(21 citation statements)

References 15 publications

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“…We observe the formation of dark stripes at the nanowire corners, indicating Al enrichment. This accumulation is consistent with the difference in chemical potential and adatom mobility on (110) and (112)-type facets [17][18][19][20] . More intriguing is the morphology of some stripes at the end of the Al x Ga 1−x As layer (Fig.…”

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confidence: 70%

Self-assembled quantum dots in a nanowire system for quantum photonics

et al. 2013

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Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-innanowire system that reproducibly self-assembles in core-shell GaAs/AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solid-state lighting devices and third-generation solar cells. S emiconductor quantum dots have been shown to be excellent building blocks for quantum photonics applications, such as single-photon sources and nano-sensing. Desirable properties of a single-photon emitter include high-fidelity anti-bunching (very small g 2 (t = 0)), narrow emission lines (ideally transform limited to a few microelectronvolt) and high brightness (>1 MHz count rate on standard detector). For simplicity, these properties should be achieved either with electrical injection or non-resonant optical excitation. Desirable properties of a nano-sensor include a high sensitivity to local electric and magnetic fields, with the quantum dot located as close as possible to the target region. A popular realization involves Stranski-Krastanow InGaAs quantum dots embedded in a three-dimensional matrix, which are excellent building blocks for the realization of practical singlephoton sources 1 . However, the photon extraction out of the bulk semiconductor is highly inefficient on account of the large mismatch in refractive indices of GaAs and vacuum. An attractive way forward is to embed the quantum dots in a nanowire 2 . To solve the extraction problem, the nanowire is designed to operate as a single-mode waveguide, a so-called photonic nanowire, with a taper as photon out-coupler 3 . Also, for nano-sensing applications, a quantum dot in a nanowire can be located much closer to the active medium. Top-down fabrication of the photonic waveguide is technologically complex, however. Bottom-up fabrication of the photonic waveguide is very attractive 4-6 , but it is at present challenging to self-assemble quantum dots in the nanowires with narrow linewidths and high yields 7,8 . Nano-sensing applications are at present not highly developed. Other degrees of freedom of the quantum-dot-in-nanowire system that can be usefully exploited are the mechanical modes ...

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confidence: 70%

Self-assembled quantum dots in a nanowire system for quantum photonics

et al. 2013

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“…The high-contrast stripe along the diagonal in Fig. 1(c) is an accumulation of Al adatoms, which occurs due to the slower diffusion of Al compared to Ga. 21,22 While previous high-resolution TEM measurements were restricted to a corner-overgrown test structure with AlAs/GaAs interfaces, 21 exploiting the increased contrast between AlAs and GaAs, the images presented here show for the first time that the GaAs/AlGaAs interfaces of corner-overgrown transport samples yield corner profiles with similar nanometer-scale sharpness.…”

Section: Tem and Corner Sharpness In The Transport Structurementioning

confidence: 99%

“…21 For example, the onedimensional accumulation wire in Fig. 3 is predicted to exist at B = 0 in the corner-overgrown heterostructures if the diameter of curvature at the corner 2r is smaller than half the Fermi wavelength λ F .…”

Section: Tem and Corner Sharpness In The Transport Structurementioning

confidence: 99%

“…3 is predicted to exist at B = 0 in the corner-overgrown heterostructures if the diameter of curvature at the corner 2r is smaller than half the Fermi wavelength λ F . 21 For typical sheet electron densities between 1.0 × 10 11 and 1.5 × 10 11 cm −2 , λ F is between 80 and 65 nm. With 2r = 5.7 nm, as evident from Fig.…”

Section: Tem and Corner Sharpness In The Transport Structurementioning

confidence: 99%

“…The measurements show a corner profile of nanometer-scale sharpness similar to the diagnostic samples studied in Ref. 21. Hartree simulations of these heterostructures are helpful for understanding the electronic states that exist in such nonplanar junctions of two quantum wells and help to interpret their This paper will review the bent quantum well system at both zero magnetic field and at high fields of equal filling factor on both facets.…”

Section: Introductionmentioning

confidence: 99%

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Hartree simulations of coupled quantum Hall edge states in corner-overgrown heterostructures

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The electronic states in a corner-overgrown bent GaAs/AlGaAs quantum well heterostructure are studied with numerical Hartree simulations. Transmission electron microscope pictures of the junction sharpness are shown to justify the sharp-corner potential assumed for these calculations. In a tilted magnetic field, both facets of the bent quantum well are brought to a quantum Hall (QH) state, and the corner hosts an unconventional hybrid system of coupled counter-propagating quantum Hall edges and an additional 1D accumulation wire. We show how, in contrast to coplanar barrier-junctions of QH systems, the coupling between the three subsystems increases as a function of the applied magnetic field, and discuss the implications of the numerical results for the interpretation of experimental data on bent quantum Hall systems reported elsewhere.

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