Role of the Au/GaAs(111) interface on the wurtzite-structure formation during GaAs nanowire growth by a vapor-liquid-solid mechanism

Toru Akiyama, Yuya Haneda, Kohji Nakamura, and Tomonori Ito

Phys. Rev. B 79, 153406 – Published 16 April 2009

Abstract

An ab initio study on the formation of GaAs layers with wurtzite structure during GaAs nanowire growth is performed for Au/GaAs(111) interfaces. The calculations reveal that Au atoms can be incorporated and stabilize the wurtzite structure at the $Au / GaAs (111) B$ interface. The zinc-blende structure, in contrast, is favorable at the $Au / GaAs (111) A$ interface, implying that wurtzite segments such as rotational twins can be formed only when the $GaAs (111) B$ substrate is used to fabricate GaAs nanowires by vapor-solid-liquid (VLS) growth. The stabilization of wurtzite structure originates from the hybridization between incorporated Au and interfacial As atoms which enhances the electrostatic interaction between anions and cations of GaAs layers. The results provide a possible explanation for wurtzite-structure formation in GaAs nanowires by the VLS growth on the $GaAs (111) B$ substrate.

Received 25 January 2009

DOI:https://doi.org/10.1103/PhysRevB.79.153406

Authors & Affiliations

Toru Akiyama^*, Yuya Haneda, Kohji Nakamura, and Tomonori Ito

Department of Physics Engineering, Mie University, 1577 Kurima-Machiya, Tsu 514-8507, Japan

^*akiyama@phen.mie-u.ac.jp

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Issue

Vol. 79, Iss. 15 — 15 April 2009

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Images

Figure 1
(Color online) Geometries of $Au / GaAs (111) B$ (a) without W segment and with (b) one and (c) two bilayers of W segments along the [111] direction. Purple (filled), white (open), and brown (gray) circles represent Ga, As, and Au atoms, respectively. Positions of interstitial Au atoms are indicated by symbols A, B, C, and D. The bottom bilayers and artificial hydrogen atoms are truncated for simplicity. Same models with Ga-terminated interfaces are considered.Reuse & Permissions
Figure 2
(Color online) Calculated energy difference between ZB and W structures as a function of distance between the position of interstitial Au and the interface for $Au / GaAs (111) A$ (circles) and $Au / GaAs (111) B$ (squares). The position of the interface is defined as the (averaged) midpoint between the top layer of GaAs and bottom Au atom. The origin of the energy difference indicates bistability exhibiting both ZB and W structures. Black (filled) and red (empty) symbols represent the energy differences for the interfaces with one- and two-bilayer W segments, respectively. The horizontal axis for each plot represents the calculated distance between Au and the interface with ZB structure. The energy differences between ZB and W structures without Au interstitial atoms calculated using $Au / GaAs (111) A$ $(Au / GaAs (111) B)$ interfaces are shown by horizontal solid (dashed) lines.Reuse & Permissions
Figure 3
(Color online) Calculated incorporation energy of interstitial Au atom as a function of its distance from the interface for (a) $Au / GaAs (111) A$ and (b) $Au / GaAs (111) B$ interfaces. Circles, squares, and diamonds represent the formation energy for the interfaces without W segments, with one-bilayer W segment, and with two-bilayer W segments, respectively. The shaded area indicates the stable region for the interface incorporating Au atoms. The incorporation energy of Au in bulk GaAs obtained by the 64 atom supercell is shown by dashed lines.Reuse & Permissions
Figure 4
(Color online) Charge-density difference, $Δ ρ (r)$ , between Au/GaAs(111) with interstitial Au atom at the interface and a simple sum of Au/GaAs(111) without interstitial Au and Au atom for (a) $Au / GaAs (111) B$ without W segments, (b) $Au / GaAs (111) B$ with one-bilayer W segment, (c) $Au / GaAs (111) A$ without W segments, and (d) $Au / GaAs (111) A$ with one-bilayer W segment. The positive (accumulated) and negative (depleted) values of $Δ ρ (r)$ are represented by blue (dark) and yellow (bright) regions, respectively. Isosurfaces are $\pm 0.008 e / Å^{3}$ . Interatomic distances are also shown.Reuse & Permissions

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