Lithography-free variation of the number density of self-catalyzed GaAs nanowires and its impact on polytypism

Schroth, Philipp; Jakob, Julian; Feigl, Ludwig; Kashani, Seyed Mohammad Mostafavi; Pietsch, U.; Baumbach, Tilo

doi:10.1557/mrc.2018.145

Cited by 8 publications

(12 citation statements)

References 33 publications

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“…During the processing with supply of both Ga and As, also the difference between the two peaks along q z was observed to evolve. The NW remains mainly in the ZB phase; however, the peak associated with pure WZ moved toward the ZB peak, indicating a change of the polytype mixture during the additional growth, similar to ref .…”

Section: Resultssupporting

confidence: 81%

X-ray Diffraction Analysis of the Angular Stability of Self-Catalyzed GaAs Nanowires for Future Applications in Solar-Light-Harvesting and Light-Emitting Devices

Kashani

Kriegner

Bahrami

et al. 2019

ACS Appl. Nano Mater.

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Semiconductor nanowires are a class of materials that recently have gained increasing interest in solar-cell applications and light-emitting devices. Finding reproducible processing conditions is fundamental for their future mass production. In this work, the stability of individual epitaxial GaAs nanowires (NWs) under molecular beam epitaxy (MBE) processing conditions is studied by means of a time-resolved in situ micro X-ray diffraction (μXRD) method and scanning electron microscopy. Our proposed μXRD method is a nondestructive characterization technique where individual nanoobjects of different dimensions, crystal orientations, and structures are detectable under MBE processing conditions. NWs were grown by self-catalyzed MBE onto prepatterned Si(111) substrate. When exposed to MBE processing conditions at 610 °C without supply of a source material, or with only an arsenic (As) supply, we observe evaporation from the facets with no indication of gallium (Ga) droplet formation. Furthermore, the NWs, which are initially grown perpendicularly to the substrate surface, become angularly unstable; i.e., the NWs tilt and eventually lie down on the substrate surface. Before falling down, our μXRD data evidenced vibration/bending of the NWs. Interestingly, when exposed to the original growth conditions, which include Ga and As supply, the vibrations/bendings are suppressed and the tilting can be reversed. The findings in this paper can also provide insights toward the engineering of self-catalyzed GaAs NW growth by the removal of parasitic growth objects, which inevitably grow together with NWs.

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Section: Resultssupporting

confidence: 81%

X-ray Diffraction Analysis of the Angular Stability of Self-Catalyzed GaAs Nanowires for Future Applications in Solar-Light-Harvesting and Light-Emitting Devices

Kashani

Kriegner

Bahrami

et al. 2019

ACS Appl. Nano Mater.

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“…Especially in self-catalyzed VLS growth, the local availability of growth species is even more crucial because it influences the chemical composition and the shape of the liquid catalyst droplet. This liquid droplet plays a key role in growth: its shape, particularly its volume, is responsible for the evolution of crystal shape (tapering), ,, and its wetting angle determines the crystal structure (polytypism). − Previously, the effect of NW area density on the local growth conditions was investigated for self-catalyzed NWs. , However, if the additional effect of shadowing in ordered arrays of NWs has a direct impact on the NW crystal structure as well is so far not known.…”

Section: Resultsmentioning

confidence: 99%

“…For each array, we recorded the 3D distribution of scattered X-ray intensity ex situ in the vicinity of the symmetric Si(111) and GaAs(111) Bragg reflections, illustrated in so-called reciprocal space maps (RSMs). Because the (111) lattice-plane spacing of cubic zinc-blende (ZB) GaAs and hexagonal Wurtzite (WZ) GaAs differ, , the scattering experiment is sensitive to the average stacking sequence of polytypic segments along the NW [111] growth axis. , Tilted or kinked NWs do not fulfill the Bragg’s condition simultaneously with the vertical NWs and, therefore, do not participate in the measured X-ray scattering signal. Moreover and due to the coherence properties of the X-ray beam next to the Si crystal-truncation rod (CTR) that arises from the truncation of the Si-crystal, the lateral periodicity p of the GaAs NWs gives rise to so-called superstructure rods (SR) next to the GaAs(111) Bragg reflection.…”

Section: Resultsmentioning

confidence: 99%

Impact of the Shadowing Effect on the Crystal Structure of Patterned Self-Catalyzed GaAs Nanowires

et al. 2019

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The growth of regular arrays of uniform III−V semiconductor nanowires is a crucial step on the route toward their application-relevant large-scale integration onto the Si platform. To this end, not only does optimal vertical yield, length, and diameter uniformity have to be engineered, but also, control over the nanowire crystal structure has to be achieved. Depending on the particular application, nanowire arrays with varying area density are required for optimal device efficiency. However, the nanowire area density substantially influences the nanowire growth and presents an additional challenge for nanowire device engineering. We report on the simultaneous in situ X-ray investigation of regular GaAs nanowire arrays with different area density during self-catalyzed vapor−liquid−solid growth on Si by molecular-beam epitaxy. Our results give novel insight into selectivearea growth and demonstrate that shadowing of the Ga flux, occurring in dense nanowire arrays, has a crucial impact on the evolution of nanowire crystal structure. We observe that the onset of Ga flux shadowing, dependent on array pitch and nanowire length, is accompanied by an increase of the wurtzite formation rate. Our results moreover reveal the paramount role of the secondary reflected Ga flux for VLS NW growth (specifically, that flux that is reflected directly into the liquid Ga droplet).

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“…Au-free, binary InAs [ 13 , 34 , 77 ] and GaAs [ 78 , 79 ] NWs usually display the zincblende (ZB) and wurtzite (WZ) phase mixture. This has mostly been associated with the lower surface energy of the WZ phase in comparison to the corresponding crystalline orientation of the ZB material.…”

Section: Surfactant Effect Of Sbmentioning

confidence: 99%

Recent Progress on the Gold-Free Integration of Ternary III–As Antimonide Nanowires Directly on Silicon

Anyebe

2020

Nanomaterials

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During the last few years, there has been renewed interest in the monolithic integration of gold-free, Ternary III–As Antimonide (III–As–Sb) compound semiconductor materials on complementary metal-oxide-semiconductor (CMOS)—compatible silicon substrate to exploit its scalability, and relative abundance in high-performance and cost-effective integrated circuits based on the well-established technology. Ternary III–As–Sb nanowires (NWs) hold enormous promise for the fabrication of high-performance optoelectronic nanodevices with tunable bandgap. However, the direct epitaxial growth of gold-free ternary III–As–Sb NWs on silicon is extremely challenging, due to the surfactant effect of Sb. This review highlights the recent progress towards the monolithic integration of III–As–Sb NWs on Si. First, a comprehensive and in-depth review of recent progress made in the gold-free growth of III–As–Sb NWs directly on Si is explicated, followed by a detailed description of the root cause of Sb surfactant effect and its influence on the morphology and structural properties of Au-free ternary III–As–Sb NWs. Then, the various strategies that have been successfully deployed for mitigating the Sb surfactant effect for enhanced Sb incorporation are highlighted. Finally, recent advances made in the development of CMOS compatible, Ternary III–As–Sb NWs based, high-performance optoelectronic devices are elucidated.

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Lithography-free variation of the number density of self-catalyzed GaAs nanowires and its impact on polytypism

Abstract: Abstract

Cited by 8 publications

References 33 publications

X-ray Diffraction Analysis of the Angular Stability of Self-Catalyzed GaAs Nanowires for Future Applications in Solar-Light-Harvesting and Light-Emitting Devices

X-ray Diffraction Analysis of the Angular Stability of Self-Catalyzed GaAs Nanowires for Future Applications in Solar-Light-Harvesting and Light-Emitting Devices

Impact of the Shadowing Effect on the Crystal Structure of Patterned Self-Catalyzed GaAs Nanowires

Recent Progress on the Gold-Free Integration of Ternary III–As Antimonide Nanowires Directly on Silicon

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