Ga-assisted growth of GaAs nanowires on silicon, comparison of surface SiOx of different nature

Matteini, Federico; Tütüncüoǧlu, Gözde; Rüffer, Daniel; Alarcón-Lladó, Esther; Morral, Anna Fontcuberta i

doi:10.1016/j.jcrysgro.2014.07.034

Cited by 50 publications

(55 citation statements)

References 44 publications

(64 reference statements)

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“…Dimerization of two Ga adatoms at the rate K 3 will subsequently lead (with a certain probability) to the nucleation of Ga nanodroplets and ultimately nanowires. Both processes are expected to be associated with the formation of 'craters' or even the openings penetrating through the oxide toward the substrate surface [29,33,34]. Therefore, the rate constants K 3 and K 35 should be orders of magnitude lower than that given by the effective Ga diffusivities (σ 3 D 3 and σ 35 D 3 , with σ as the corresponding capture coefficients [35][36][37]).…”

Section: The Modelmentioning

confidence: 99%

Tailoring the diameter and density of self-catalyzed GaAs nanowires on silicon

et al. 2015

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Nanowire diameter has a dramatic effect on the absorption cross-section in the optical domain. The maximum absorption is reached for ideal nanowire morphology within a solar cell device. As a consequence, understanding how to tailor the nanowire diameter and density is extremely important for high-efficient nanowire-based solar cells. In this work, we investigate mastering the diameter and density of self-catalyzed GaAs nanowires on Si(111) substrates by growth conditions using the self-assembly of Ga droplets. We introduce a new paradigm of the characteristic nucleation time controlled by group III flux and temperature that determine diameter and length distributions of GaAs nanowires. This insight into the growth mechanism is then used to grow nanowire forests with a completely tailored diameter-density distribution. We also show how the reflectivity of nanowire arrays can be minimized in this way. In general, this work opens new possibilities for the cost-effective and controlled fabrication of the ensembles of self-catalyzed III-V nanowires for different applications, in particular in next-generation photovoltaic devices.S Online supplementary data available from stacks.iop.org/NANO/26/105603/mmedia

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Section: The Modelmentioning

confidence: 99%

Tailoring the diameter and density of self-catalyzed GaAs nanowires on silicon

et al. 2015

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“…18,19,24−30 However, to date, full control over nanowire orientation was observed to be dependent on the wafer batch. 31,32 Most studies focus on the comprehension of the growth at the steady state. To the best of our knowledge, very little work has targeted the understanding of the initial steps of growth.…”

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“…It also indicates a change in the nature of the oxide. 36,37 In order to further illustrate the change in the nature of the native oxide and to relate it to what one generally observes in nanowire growth, 32 we look at the contact angle of the Ga droplets, β (Figure 3). By progressively increasing the native oxide thickness (0.4, 0.6, 0.9, 1.1, 1.2, and 1.5 nm) the contact angle increases from 50°up to ∼120°(see, respectively, Figure 3a−f).…”

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Wetting of Ga on SiO_x and Its Impact on GaAs Nanowire Growth

Matteini

Tütüncüoǧlu

Potts

et al. 2015

Crystal Growth & Design

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Ga-assisted growth of GaAs nanowires on silicon provides a path for integrating highpurity III−Vs on silicon. The nature of the oxide on the silicon surface has been shown to impact the overall possibility of nanowire growth and their orientation with the substrate. In this work, we show that not only the exact thickness, but also the nature of the native oxide determines the feasibility of nanowire growth. During the course of formation of the native oxide, the surface energy varies and results in a different contact angle of Ga droplets. We find that, only for a contact angle around 90°( i.e., oxide thickness ∼0.9 nm), nanowires grow perpendicularly to the silicon substrate. This native oxide engineering is the first step toward controlling the self-assembly process, determining mainly the nanowire density and orientation.

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“…The increase of the NW density is associated with the increase of the pinhole density, which can be controlled by the reduction of the oxide layer thickness [116]. But if the oxide thickness is too thin or even oxide free, it will lead to the 2D epitaxial growth such as clusters or thin film, rather than NW growth [122,123]. It is also suggested that the increase of NW density can be achieved by increasing the mask surface roughness [114,123].…”

Section: Influence Of the Substrate And Its Preparationmentioning

confidence: 99%

Elongated nanostructures for radial junction solar cells

et al. 2013

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In solar cell technology, the current trend is to thin down the active absorber layer. The main advantage of a thinner absorber is primarily the reduced consumption of material and energy during production. For thin film silicon (Si) technology, thinning down the absorber layer is of particular interest since both the device throughput of vacuum deposition systems and the stability of the devices are significantly enhanced. These features lead to lower cost per installed watt peak for solar cells, provided that the (stabilized) efficiency is the same as for thicker devices. However, merely thinning down inevitably leads to a reduced light absorption. Therefore, advanced light trapping schemes are crucial to increase the light path length. The use of elongated nanostructures is a promising method for advanced light trapping. The enhanced optical performance originates from orthogonalization of the light's travel path with respect to the direction of carrier collection due to the radial junction, an improved anti-reflection effect thanks to the three-dimensional geometric configuration and the multiple scattering between individual nanostructures. These advantages potentially allow for high efficiency at a significantly reduced quantity and even at a reduced material quality, of the semiconductor material. In this article, several types of elongated nanostructures with the high potential to improve the device performance are reviewed. First, we briefly introduce the conventional solar cells with emphasis on thin film technology, following the most commonly used fabrication techniques for creating nanostructures with a high aspect ratio. Subsequently, several representative applications of elongated nanostructures, such as Si nanowires in realistic photovoltaic (PV) devices, are reviewed. Finally, the scientific challenges and an outlook for nanostructured PV devices are presented.

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Ga-assisted growth of GaAs nanowires on silicon, comparison of surface SiOx of different nature

Cited by 50 publications

References 44 publications

Tailoring the diameter and density of self-catalyzed GaAs nanowires on silicon

Tailoring the diameter and density of self-catalyzed GaAs nanowires on silicon

Wetting of Ga on SiO_x and Its Impact on GaAs Nanowire Growth

Elongated nanostructures for radial junction solar cells

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Ga-assisted growth of GaAs nanowires on silicon, comparison of surface SiOx of different nature

Cited by 50 publications

References 44 publications

Tailoring the diameter and density of self-catalyzed GaAs nanowires on silicon

Tailoring the diameter and density of self-catalyzed GaAs nanowires on silicon

Wetting of Ga on SiOx and Its Impact on GaAs Nanowire Growth

Elongated nanostructures for radial junction solar cells

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Product

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Wetting of Ga on SiO_x and Its Impact on GaAs Nanowire Growth