Impact of the Ga Droplet Wetting, Morphology, and Pinholes on the Orientation of GaAs Nanowires

Matteini, Federico; Tütüncüoǧlu, Gözde; Mikulik, Dmitry; Vukajlovic-Plestina, Jelena; Potts, Heidi; Leran, Jean-Baptiste; Carter, W. Craig; Morral, Anna Fontcuberta i

doi:10.1021/acs.cgd.6b00858

Cited by 40 publications

(47 citation statements)

References 36 publications

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“…With respect to the oxide thickness we find that a thicker oxide favors the formation of tilted nanowires. This result can be compared to the work by Matteini et al, 24 where a thicker native silicon oxide was found to favor spilling of gallium droplets and therefore nucleation of tilted nanowires. Whether or not the explanation of the surface energy also applies in our case is subject to further investigation.…”

Section: ■ Results and Discussionsupporting

confidence: 56%

Tilting Catalyst-Free InAs Nanowires by 3D-Twinning and Unusual Growth Directions

Potts

Hees

Tütüncüoǧlu

et al. 2017

Crystal Growth & Design

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Controlling the growth direction of nanowires is of strategic importance both for applications where nanowire arrays are contacted in parallel and for the formation of more complex nanowire networks. We report on the existence of tilted InAs nanowires on (111)B GaAs. The tilted direction is predominantly the result of a three-dimensional twinning phenomenon at the initial stages of growth, so far only observed in VLS growth. We also find some nanowires growing in ⟨112⟩ and other directions. We further demonstrate how the tilting of nanowires can be engineered by modifying the growth conditions, and outline the procedures to achieve fully vertical or tilted nanowire ensembles. Conditions leading to a high density of tilted nanowires also provide a way to grow nanoscale crosses. This work opens the path toward achieving control over nanowire structures and related hierarchical structures. ■ INTRODUCTIONSemiconductor nanowires are promising candidates for future electronic, optoelectronic, and energy harvesting devices as well as a platform to investigate low-dimensional phenomena.1−8 In certain applications such as light emitting diodes or solar cells, it is highly desirable that nanowires are contacted in parallel on as-grown substrates. In this case, a complete control of the nanowire growth direction is essential in order to avoid leakage or open-circuit pathways. For other applications such as Majorana Fermion quantum computing, the growth direction determines the g-factor and spin−orbit interaction. In addition, any quantum logic involving Majorana Fermions requires more than one branch, e.g., nanowire crosses are desired. 9−11In general, III−V nanowires grow preferentially in the ⟨111⟩B direction, resulting in mostly vertical nanowires when grown on (111)B substrates. Interest in nonconventional growth directions has increased significantly during the last years, and in the case of metal-catalyzed nanowires, a variety of different directions have been reported.12 Recent examples include ⟨111⟩A oriented GaAs and GaSb nanowires, 13,14 and InP nanowires for which the direction can be switched between ⟨111⟩B and ⟨100⟩.15 In addition, InAs nanowires in ⟨001⟩ direction and ⟨112⟩ direction have been demonstrated for goldcatalyzed MOVPE growth. 16 The change in growth direction has been attributed to a change of contact angle of the liquid droplet in the vapor−liquid−solid (VLS) mechanism, or by dynamics at the growth interface. Recently, unconventional growth directions have also been observed for self-catalyzed nanowires. A small fraction of GaAsSb nanowires was found to grow in ⟨112⟩ direction, 17 GaAs nanowires in the ⟨111⟩A direction have been engineered, 18 and InAs nanowires turning from ⟨111⟩B to ⟨112̅ ⟩ direction have been demonstrated. 19,20 However, tilted nanowires are not in all cases related to the growth in nonconventional crystalline directions. In some cases they can also explained by nucleation from parasitic growth (no crystalline relation with the substrate) or by multiple-order thr...

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Section: ■ Results and Discussionsupporting

confidence: 56%

Tilting Catalyst-Free InAs Nanowires by 3D-Twinning and Unusual Growth Directions

Potts

Hees

Tütüncüoǧlu

et al. 2017

Crystal Growth & Design

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“…31 Increased oxide thickness or hole density might prevent the appearance of crawling objects. [32][33][34][35] Fig. 2(b) and (c) show the cross-sectional SEM images of another sample in the two perpendicular cleaving directions.…”

Section: Resultsmentioning

confidence: 99%

Optimizing the yield of A-polar GaAs nanowires to achieve defect-free zinc blende structure and enhanced optical functionality

et al. 2018

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Compound semiconductors exhibit an intrinsic polarity, as a consequence of the ionicity of their bonds. Nanowires grow mostly along the (111) direction for energetic reasons. Arsenide and phosphide nanowires grow along (111)B, implying a group V termination of the (111) bilayers. Polarity engineering provides an additional pathway to modulate the structural and optical properties of semiconductor nanowires. In this work, we demonstrate for the first time the growth of Ga-assisted GaAs nanowires with (111)A-polarity, with a yield of up to ∼50%. This goal is achieved by employing highly Ga-rich conditions which enable proper engineering of the energies of A and B-polar surfaces. We also show that A-polarity growth suppresses the stacking disorder along the growth axis. This results in improved optical properties, including the formation of AlGaAs quantum dots with two orders or magnitude higher brightness. Overall, this work provides new grounds for the engineering of nanowire growth directions, crystal quality and optical functionality.

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“…The reduction of the NW density with decrease in growth temperature therefore suggests that the reduced desorption of the Ga adatoms from the substrate may balance the reduction in droplet volume to some extent, but it cannot compensate for other effects. These have a deleterious impact on nanowire nucleation 39 . Therefore, we suggest that lowering the substrate temperature to 600 °C results in a reduction in the density of the droplets, which can retain the optimum volume for NW nucleation, leading to uneven 2D growth.…”

Section: Resultsmentioning

confidence: 99%

A Two-Step Growth Pathway for High Sb Incorporation in GaAsSb Nanowires in the Telecommunication Wavelength Range

Ahmad

Karim

Hafiz

et al. 2017

Sci Rep

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Self-catalyzed growth of axial GaAs1−xSbx nanowire (NW) arrays with bandgap tuning corresponding to the telecommunication wavelength of 1.3 µm poses a challenge, as the growth mechanism for axial configuration is primarily thermodynamically driven by the vapor-liquid-solid growth process. A systematic study carried out on the effects of group V/III beam equivalent (BEP) ratios and substrate temperature (Tsub) on the chemical composition in NWs and NW density revealed the efficacy of a two-step growth temperature sequence (initiating the growth at relatively higher Tsub = 620 °C and then continuing the growth at lower Tsub) as a promising approach for obtaining high-density NWs at higher Sb compositions. The dependence of the Sb composition in the NWs on the growth parameters investigated has been explained by an analytical relationship between the effective vapor composition and NW composition using relevant kinetic parameters. A two-step growth approach along with a gradual variation in Ga-BEP for offsetting the consumption of the droplets has been explored to realize long NWs with homogeneous Sb composition up to 34 at.% and photoluminescence emission reaching 1.3 µm at room temperature.

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Impact of the Ga Droplet Wetting, Morphology, and Pinholes on the Orientation of GaAs Nanowires

Cited by 40 publications

References 36 publications

Tilting Catalyst-Free InAs Nanowires by 3D-Twinning and Unusual Growth Directions

Tilting Catalyst-Free InAs Nanowires by 3D-Twinning and Unusual Growth Directions

Optimizing the yield of A-polar GaAs nanowires to achieve defect-free zinc blende structure and enhanced optical functionality

A Two-Step Growth Pathway for High Sb Incorporation in GaAsSb Nanowires in the Telecommunication Wavelength Range

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