Effects of Gold Diffusion on n-Type Doping of GaAs Nanowires

Tambe, Michael; Ren, Shenqiang; Gradečak, Silvija

doi:10.1021/nl102594e

Cited by 51 publications

(40 citation statements)

References 44 publications

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“…[5][6][7][8] shows that close to the tip the three types of nanowires are characterized by different crystal structures: NWs of the first type exhibit ZB structure in contact with the Ga nanoparticle ( Fig. 5(a) and 5(b)), NWs of the second type exhibit WZ structure in the same region (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, an increasing effort has been devoted by to develop NW growth methods that avoid the use of Au or any other foreign catalytic materials, to avoid contamination from catalyst incorporation during growth. [4][5][6] In the case of GaAs, Au-free NW growth has been obtained for selected substrate and growth conditions, with Ga nanoparticles found at the tip of the resulting NWs. [7][8][9][10][11][12][13][14] Using a VLS-like model, NW growth has been associated with the formation of Ga nanoparticles, which promote one-dimensional growth.…”

Section: Introductionmentioning

confidence: 99%

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Vapor-liquid-solid and vapor-solid growth of self-catalyzed GaAs nanowires

et al. 2011

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We report on the morphological and structural properties of GaAs nanowires nucleated by self-catalyzed vapor-liquid-solid processes by molecular beam epitaxy on Si-treated GaAs substrates. We found that GaAs nanowires display zincblende and/or wurtzite phase depending on the As/Ga abundance ratio at the growth front, that determines the size and supersaturation of the Ga nanoparticles at the nanowire tip. We also found that even when growth conditions lead to the disappearance of such Ga nanoparticles, preferential one-dimensional growth continues through a vapor-solid mechanism. The nanowire portions grown by vapor solid mechanism display zincblend structure

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vapor-liquid-solid and vapor-solid growth of self-catalyzed GaAs nanowires

et al. 2011

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“…This could lead to growth of non-stoichiometric, Ga-enriched GaAs. 7,11 The incorporation of Ga 2− As will counteract the n-doping by deliberately added donor species. This may explain why it is rather difficult to obtain n-type conductivity in ZB GaAs nanowires, and only high concentrations of Sn Ga have proven successful so far.…”

Section: −mentioning

confidence: 99%

“…However, an Au droplet that accelerates an underneath growing nanowire can also leave impurities within the GaAs nanowire. 11,12 Previous experimental efforts have focused on characterizing Au defect levels within a GaAs crystal, [13][14][15] . Moreover, experimental studies employing X-ray energy-dispersive spectroscopy 7,11 indicate deviations from stoichiometry in the nanowires close to the growth zone, and thus point to the abundant intrinsic defects, in addition to Au impurities, in GaAs nanowires.…”

Section: Introductionmentioning

confidence: 99%

As vacancies, Ga antisites, and Au impurities in zinc blende and wurtzite GaAs nanowire segments from first principles

Du¹,

Sakong²,

Kratzer³

2013

Phys. Rev. B

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In this paper some specific issues related to point defects in GaAs nanowires are addressed with the help of density functional theory calculations. These issues mainly arise from the growth of nanowires under conditions different from those used for thin films or bulk GaAs, such as the co-existence of zincblende and wurtzite polytypes, the use of gold particles as catalyst, and the arsenic-limited growth regime. Hence, we carry out density-functional calculations for As vacancies, GaAs antisites, and Au impurities in ZB and WZ GaAs crystals. Our results show that As vacancies can diffuse within in a ZB GaAs crystal with migration barriers of ∼1.9 eV. Within WZ GaAs, As vacancy diffusion is found to be anisotropic, with low barriers of 1.60 up to 1.79 eV (depending on doping conditions) in the ab-plane, while there are higher barriers of 2.07 to 2.44 eV to diffuse along the c-axis. The formation energy of Au impurities is found to be generally much lower than those of arsenic vacancies or GaAs antisites. Thus, Au impurities will be the dominant defects formed in Au-catalyzed nanowire growth. Moreover, we find that it is energetically more favorable by 1 to 2 eV for an Au impurity to replace a lattice Ga atom than a lattice As atom in GaAs. An Au substitutional defect for a lattice Ga atom in ZB GaAs is found to create a charge transfer level in the lower half of the band gap. While our calculations locate this level at Ev + 0.22 eV, taking into account the inaccuracy of the density functional that ought to be corrected by a downshift of Ev by about 0.2 eV results in good agreement with the experimental result of Ev + 0.4 eV.

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“…For this, the understanding of the growth process of a nanowire is important. Bottom-up grown nanowires are typically formed via the Vapor-Liquid-Solid (VLS) mechanism [6][7][8] , where a nanoscale liquid droplet acts as a catalyst for nanowire crystal formation. It is generally accepted that incorporation paths of dopants are similar from the growth precursors and result either from the radial growth of the nanowire or through diffusion through the catalyst [9][10][11][12][13][14] .…”

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confidence: 99%

Doping incorporation paths in catalyst-free Be-doped GaAs nanowires

Casadei

Krogstrup

Heiß

et al. 2013

Applied Physics Letters

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The incorporation paths of Be in GaAs nanowires grown by the Ga-assisted method in molecular beam epitaxy have been investigated by electrical measurements of nanowires with different doping profiles. We find that Be atoms incorporate preferentially via the nanowire side facets, while the incorporation path through the Ga droplet is negligible. We also show that Be can diffuse into the volume of the nanowire giving an alternative incorporation path. This work is an important step towards controlled doping of nanowires and will serve as a help for designing future devices based on nanowires.

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Effects of Gold Diffusion on n-Type Doping of GaAs Nanowires

Cited by 51 publications

References 44 publications

Vapor-liquid-solid and vapor-solid growth of self-catalyzed GaAs nanowires

Vapor-liquid-solid and vapor-solid growth of self-catalyzed GaAs nanowires

As vacancies, Ga antisites, and Au impurities in zinc blende and wurtzite GaAs nanowire segments from first principles

Doping incorporation paths in catalyst-free Be-doped GaAs nanowires

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