Suppression of three dimensional twinning for a 100% yield of vertical GaAs nanowires on silicon

Russo-Averchi, Eleonora; Heiß, Martin; Michelet, Lionel; Krogstrup, Peter; Nygård, Jesper; Magén, Cesar; Morante, J.R.; Uccelli, Emanuele; Arbiol, Jordi; Morral, Anna Fontcuberta i

doi:10.1039/c2nr11799a

Cited by 78 publications

(62 citation statements)

References 26 publications

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“…An increasing V/IIII ratio was found to reduce the number of tilted NWs to some extent, although it could not be completely avoided. This increase in vertical NWs with a high V/III ratio could be associated with the reduction of the three-dimensional multiple order twinning [101]. On the other hand, no noticeable change in the yield of vertical NWs was found with the change in the growth temperature.…”

Section: Self-catalyzed Nws On Simentioning

confidence: 80%

Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

et al. 2014

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This thesis deals with the growth of GaAs nanowires (NWs) by molecular beam epitaxy (MBE) using vapor-liquid-solid method on various substrates including GaAs(111)B, Si(111) and graphene. The growth of the NWs on GaAs substrates was carried out by Au-catalyzed technique, whereas the growths on Si and graphene substrates were carried out using self-catalyzed technique that has been the main focus of this thesis. The long-term goal of this work was to produce p-n radial junction GaAs NWs for solar cell applications.Necessary conditions were established for obtaining vertical self-catalyzed GaAs NWs on Si(111), which is reproducible from run-to-run. One of the major issues in these NWs grown by both Au-and self-catalyzed techniques is their crystal structure. The Au-catalyzed GaAs NWs usually adopt a wurtzite (WZ) crystal phase, whereas the self-catalyzed NWs a zinc blende (ZB) phase. However, in both the cases the NWs contain stacking faults, rotational twins or/and a mixed crystal phase. The ZB and WZ phases show different optical properties, and one phase might be favored over other for certain applications. Therefore the crystal phase was controlled within single NWs by tuning the V/III ratio and introducing GaAsSb inserts. The change of the crystal phases was correlated with the change in the contact angle of the Ga droplet.Since the discovery of graphene, an ultra-thin two-dimensional material, the research on graphene has become an active field in recent years due to its remarkable properties including excellent electrical and thermal conductivities, mechanical strength and flexibility, and optical transparency. By growing the semiconductor NWs on graphene, a completely new hybrid system can be envisioned where the unique properties of both NWs and graphene can be utilized. Therefore we established a method for the growth of semiconductor NWs on graphene by demonstrating epitaxial growth of vertical GaAs and InAs NWs on different graphitic substrates.Core-shell heterostructure, doping, optical properties, and position controlled growth of self-catalyzed GaAs NWs were investigated. Growth of GaAs/GaAsSb coreshell NWs where the Sb content was tuned from about 10% -70% was studied. The effect of growth temperature and the Sb flux on the morphology of GaAsSb shell was investigated. In addition, by utilizing the core-shell geometry where the shell copies the crystal phase of the core, WZ phase of GaAsSb was demonstrated. Successful p-type doping of GaAs core using Be as dopant, and n-type doping of GaAs shell using Si and Te as dopants were achieved. To investigate the optical properties, GaAs/AlGaAs coreshell NWs were grown with different V/III ratios during the core growth. The NWs grown with high V/III ratio, despite containing a higher density of twinned ZB and WZ GaAs with SFs, were found to have superior optical quality as compared to the NWs grown with low V/III ratio that contain pure ZB GaAs. The observed V/III ratio dependent optical quality was correlated to the intrinsic defects such as As vac...

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Section: Self-catalyzed Nws On Simentioning

confidence: 80%

Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

et al. 2014

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“…Vertical orientation of nanowires can be achieved on Si (1 1 1) substrates in very high yields [14][15][16]. In the case of catalyst-free growth, ordered arrays of nanowires can in principle be attained by employing a patterned SiO 2 mask [15,[17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Characterization and analysis of InAs/p–Si heterojunction nanowire-based solar cell

Mallorquí¹,

Alarcón-Lladó²,

Russo-Averchi³

et al. 2014

J. Phys. D: Appl. Phys.

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The growth of compound semiconductor nanowires on the silicon platform has opened many new perspectives in the area of electronics, optoelectronics and photovoltaics. We have grown a 1 × 1 mm 2 array of InAs nanowires on p-type silicon for the fabrication of a solar cell. Even though the nanowires are spaced by a distance of 800 nm with a 3.3% filling volume, they absorb most of the incoming light resulting in an efficiency of 1.4%. Due to the unfavourable band alignment, carrier separation at the junction is poor. Photocurrent increases sharply at the surrounding edge with the silicon, where the nanowires do not absorb anymore. This is further proof of the enhanced absorption of semiconductors in nanowire form. This work brings further elements in the design of nanowire-based solar cells.

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“…The GaAs core was grown by the Ga-assisted method on a (111) silicon wafer, with conditions optimized for a high yield of vertical wires. 35 After the nanowires reached around a 10 lm length, the gallium flux was stopped, the As4 flux increased, and the a) …”

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confidence: 99%

Three-dimensional nanoscale study of Al segregation and quantum dot formation in GaAs/AlGaAs core-shell nanowires

Mancini

Fontana

Conesa‐Boj

et al. 2014

Applied Physics Letters

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GaAs/Al-GaAs core-shell nanowires fabricated by molecular beam epitaxy contain quantum confining structures susceptible of producing narrow photoluminescence (PL) and single photons. The nanoscale chemical mapping of these structures is analyzed in 3D by atom probe tomography (APT). The study allows us to confirm that Al atoms tend to segregate within the AlGaAs shells towards the vertices of the hexagons defining the nanowire cross section. We also find strong alloy fluctuations remaining AlGaAs shell, leading occasionally to the formation of quantum dots (QDs). The PL emission energies predicted in the framework of a 3D effective mass model for a QD analyzed by APT and the PL spectra measured on other nanowires from the same growth batch are consistent within the experimental uncertainties. V C 2014 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4904952] Epitaxial semiconductor quantum dots (QDs) have been extensively studied over the last three decades because of their peculiar optical properties such as narrow luminescence and single photon emission. The structure and chemical composition of QDs has traditionally been assessed by scanning tunneling microscopy (STM) or transmission electron microscopy (TEM) related techniques. 1 In the last decade, laser-assisted atom probe tomography (LA-APT) 2 has emerged as a tool for the determination of the morphology and of the chemical composition of nanoscale semiconductor heterostructures with sub-nanometer resolution in 3D. 3,4 In the past few years, several APT-based studies addressed a limited number of QD structures. 4-10 Quantum dots can be inserted in semiconductor nanowires either deterministically, with specific shape and composition, 11-14 or as self-assembled structures. [15][16][17][18] Nanowires, furthermore, represent a model system for atom probe analysis, 19-24 as they closely approximate the shape of a field-emission tip. Nevertheless, and despite the interest of nanowire-based QDs for quantum information [25][26][27][28][29] and for their integration in nanoscale optoelectronic devices, [30][31][32][33] no studies of nanowire QDs by APT have been reported yet.Core-shell GaAs/AlGaAs nanowires grown by molecular beam epitaxy (MBE) have been shown to exhibit narrow luminescence and single photon emission, ascribed to QDs forming occasionally at the external corners of the AlGaAs shells. 27 Isolated emissions centered around 670 nm ($1.85 eV) could be found by cathodoluminescence (CL) spectroscopy, with a typical mean frequency along the axis of the order of one spot per micron. 27 Previous studies of these structures performed by highresolution scanning transmission electron microscopy (HR-STEM), electron energy loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDX) indicated that QDs may form at the outer corner of the hexagon in the AlGaAs shell, at the termination of an Al-segregation region. 27,34 However, it was not possible to fully characterize the shape of the dots nor ascertain whether other mechanisms of QD formation may occ...

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Suppression of three dimensional twinning for a 100% yield of vertical GaAs nanowires on silicon

Cited by 78 publications

References 26 publications

Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

Position-Controlled Uniform GaAs Nanowires on Silicon using Nanoimprint Lithography

Characterization and analysis of InAs/p–Si heterojunction nanowire-based solar cell

Three-dimensional nanoscale study of Al segregation and quantum dot formation in GaAs/AlGaAs core-shell nanowires

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