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Patel N, Fonseka HA, Zhang Y, Church S, Al-Abri R, Sanchez A, Liu H, Parkinson P. Improving Quantum Well Tube Homogeneity Using Strained Nanowire Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2023; 15:10958-10964. [PMID: 36779871 PMCID: PMC9982810 DOI: 10.1021/acsami.2c22591] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 01/28/2023] [Indexed: 06/18/2023]
Abstract
Bottom-up grown nanostructures often suffer from significant dimensional inhomogeneity, and for quantum confined heterostructures, this can lead to a corresponding large variation in electronic properties. A high-throughput characterization methodology is applied to >15,000 nanoskived sections of highly strained GaAsP/GaAs radial core/shell quantum well heterostructures revealing high emission uniformity. While scanning electron microscopy shows a wide nanowire diameter spread of 540-60+60 nm, photoluminescence reveals a tightly bounded band-to-band transition energy of 1546-3+4 meV. A highly strained core/shell nanowire design is shown to reduce the dependence of emission on the quantum well width variation significantly more than in the unstrained case.
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Affiliation(s)
- Nikesh Patel
- Department
of Physics & Astronomy, Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - H. Aruni Fonseka
- Department
of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom
| | - Yunyan Zhang
- Department
of Electronic and Electrical Engineering, University College London, London, WC1E 6BT, United Kingdom
- School
of Micro-Nano Electronics, Zhejiang University, Hangzhou, Zhejiang 311200, China
| | - Stephen Church
- Department
of Physics & Astronomy, Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Ruqaiya Al-Abri
- Department
of Physics & Astronomy, Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Ana Sanchez
- Department
of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom
| | - Huiyun Liu
- Department
of Electronic and Electrical Engineering, University College London, London, WC1E 6BT, United Kingdom
| | - Patrick Parkinson
- Department
of Physics & Astronomy, Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
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Tailoring Morphology and Vertical Yield of Self-Catalyzed GaP Nanowires on Template-Free Si Substrates. NANOMATERIALS 2021; 11:nano11081949. [PMID: 34443778 PMCID: PMC8400893 DOI: 10.3390/nano11081949] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 07/14/2021] [Accepted: 07/26/2021] [Indexed: 12/16/2022]
Abstract
Tailorable synthesis of III-V semiconductor heterostructures in nanowires (NWs) enables new approaches with respect to designing photonic and electronic devices at the nanoscale. We present a comprehensive study of highly controllable self-catalyzed growth of gallium phosphide (GaP) NWs on template-free silicon (111) substrates by molecular beam epitaxy. We report the approach to form the silicon oxide layer, which reproducibly provides a high yield of vertical GaP NWs and control over the NW surface density without a pre-patterned growth mask. Above that, we present the strategy for controlling both GaP NW length and diameter independently in single- or two-staged self-catalyzed growth. The proposed approach can be extended to other III-V NWs.
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Petronijevic E, Belardini A, Leahu G, Hakkarainen T, Piton MR, Koivusalo E, Sibilia C. Broadband optical spin dependent reflection in self-assembled GaAs-based nanowires asymmetrically hybridized with Au. Sci Rep 2021; 11:4316. [PMID: 33619343 PMCID: PMC7900205 DOI: 10.1038/s41598-021-83899-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 12/29/2020] [Indexed: 11/09/2022] Open
Abstract
Hybridization of semiconductor nanostructures with asymmetric metallic layers offers new paths to circular polarization control and chiral properties. Here we study, both experimentally and numerically, chiral properties of GaAs-based nanowires (NWs) which have two out of six sidewalls covered by Au. Sparse ensembles of vertical, free-standing NWs were fabricated by means of lithography-free self-assembled technique on Si substrates and subsequently covered by Au using tilted evaporation. We report on optical spin-dependent specular reflection in the 680–1000 nm spectral range when the orientation of the golden layers follows the rule of extrinsic chirality. The analysis shows reflection peaks of the chiral medium whose intensity is dependent on the light handedness. We further propose a novel, time-efficient numerical method that enables a better insight into the far-field intensity and distribution of the scattered light from a sparse NW ensembles. The measurements done on three different samples in various orientations show good agreement with theoretical predictions over a broad wavelength range.
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Affiliation(s)
- Emilija Petronijevic
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy.
| | - Alessandro Belardini
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy
| | - Grigore Leahu
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy
| | - Teemu Hakkarainen
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy.,Optoelectronics Research Centre, Physics Unit, Tampere University, Korkeakoulunkatu 3, 33720, Tampere, Finland
| | - Marcelo Rizzo Piton
- Optoelectronics Research Centre, Physics Unit, Tampere University, Korkeakoulunkatu 3, 33720, Tampere, Finland
| | - Eero Koivusalo
- Optoelectronics Research Centre, Physics Unit, Tampere University, Korkeakoulunkatu 3, 33720, Tampere, Finland
| | - Concita Sibilia
- Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16, 00161, Rome, Italy
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Koivusalo E, Hilska J, Galeti HVA, Galvão Gobato Y, Guina M, Hakkarainen T. The role of As species in self-catalyzed growth of GaAs and GaAsSb nanowires. NANOTECHNOLOGY 2020; 31:465601. [PMID: 32750687 DOI: 10.1088/1361-6528/abac34] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Precise control and broad tunability of the growth parameters are essential in engineering the optical and electrical properties of semiconductor nanowires (NWs) to make them suitable for practical applications. To this end, we report the effect of As species, namely As2 and As4, on the growth of self-catalyzed GaAs based NWs. The role of As species is further studied in the presence of Te as n-type dopant in GaAs NWs and Sb as an additional group V element to form GaAsSb NWs. Using As4 enhances the growth of NWs in the axial direction over a wide range of growth parameters and diminishes the tendency of Te and Sb to reduce the NW aspect ratio. By extending the axial growth parameter window, As4 allows growth of GaAsSb NWs with up to 47% in Sb composition. On the other hand, As2 favors sidewall growth which enhances the growth in the radial direction. Thus, the selection of As species is critical for tuning not only the NW dimensions, but also the incorporation mechanisms of dopants and ternary elements. Moreover, the commonly observed dependence of twinning on Te and Sb remains unaffected by the As species. By exploiting the extended growth window associated with the use of As4, enhanced Sb incorporation and optical emission up to 1400 nm wavelength range is demonstrated. This wavelength corresponds to the telecom E-band, which opens new prospects for this NW material system in future telecom applications while simultaneously enabling their integration to the silicon photonics platform.
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Affiliation(s)
- Eero Koivusalo
- Optoelectronics Research Centre, Physics Unit, Tampere University, Tampere, Finland
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Rizzo Piton M, Hakkarainen T, Hilska J, Koivusalo E, Lupo D, Galeti HVA, Galvão Gobato Y, Guina M. Optimization of Ohmic Contacts to p-GaAs Nanowires. NANOSCALE RESEARCH LETTERS 2019; 14:344. [PMID: 31728662 PMCID: PMC6856241 DOI: 10.1186/s11671-019-3175-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/04/2019] [Indexed: 06/10/2023]
Abstract
The performance of Ohmic contacts applied to semiconductor nanowires (NWs) is an important aspect for enabling their use in electronic or optoelectronic devices. Due to the small dimensions and specific surface orientation of NWs, the standard processing technology widely developed for planar heterostructures cannot be directly applied. Here, we report on the fabrication and optimization of Pt/Ti/Pt/Au Ohmic contacts for p-type GaAs nanowires grown by molecular beam epitaxy. The devices were characterized by current-voltage (IV) measurements. The linearity of the IV characteristics curves of individual nanowires was optimized by adjusting the layout of the contact metal layers, the surface treatment prior to metal evaporation, and post-processing thermal annealing. Our results reveal that the contact resistance is remarkably decreased when a Pt layer is deposited on the GaAs nanowire prior to the traditional Ti/Pt/Au multilayer layout used for p-type planar GaAs. These findings are explained by an improved quality of the metal-GaAs interface, which was evidenced by grazing incidence X-ray diffraction measurements in similar metallic thin films deposited on GaAs (110) substrates. In particular, we show that Ti exhibits low degree of crystallinity when deposited on GaAs (110) surface which directly affects the contact resistance of the NW devices. The deposition of a thin Pt layer on the NWs prior to Ti/Pt/Au results in a 95% decrease in the total electrical resistance of Be-doped GaAs NWs which is associated to the higher degree of crystallinity of Pt than Ti when deposited directly on GaAs (110).
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Affiliation(s)
- Marcelo Rizzo Piton
- Optoelectronics Research Centre, Physics Unit, Tampere University, Tampere, Finland
- Physics Department, Federal University of São Carlos, São Carlos, Sao Paulo Brazil
| | - Teemu Hakkarainen
- Optoelectronics Research Centre, Physics Unit, Tampere University, Tampere, Finland
| | - Joonas Hilska
- Optoelectronics Research Centre, Physics Unit, Tampere University, Tampere, Finland
| | - Eero Koivusalo
- Optoelectronics Research Centre, Physics Unit, Tampere University, Tampere, Finland
| | - Donald Lupo
- Electronics and Communications Engineering, Tampere University, Tampere, Finland
| | | | - Yara Galvão Gobato
- Physics Department, Federal University of São Carlos, São Carlos, Sao Paulo Brazil
| | - Mircea Guina
- Optoelectronics Research Centre, Physics Unit, Tampere University, Tampere, Finland
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6
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Rizzo Piton M, Koivusalo E, Hakkarainen T, Galeti HVA, De Giovanni Rodrigues A, Talmila S, Souto S, Lupo D, Galvão Gobato Y, Guina M. Gradients of Be-dopant concentration in self-catalyzed GaAs nanowires. NANOTECHNOLOGY 2019; 30:335709. [PMID: 30995612 DOI: 10.1088/1361-6528/ab1a97] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Effective and controllable doping is instrumental for enabling the use of III-V semiconductor nanowires (NWs) in practical electronics and optoelectronics applications. To this end, dopants are incorporated during self-catalyzed growth via vapor-liquid-solid mechanism through the catalyst droplet or by vapor-solid mechanism of the sidewall growth. The interplay of these mechanisms together with the competition between axial elongation and radial growth of NWs can result in dopant concentration gradients along the NW axis. Here, we report an investigation of Be-doped p-type GaAs NWs grown by the self-catalyzed method on lithography-free Si/SiO x templates. The influence of dopant incorporation on the structural properties of the NWs is analyzed by scanning and transmission electron microscopy. By combining spatially resolved Raman spectroscopy and transport characterization, we are able to estimate the carrier concentration, mobility and resistivity on single-NW level. We show that Be dopants are incorporated predominantly by vapor-solid mechanism for low Be flux, while the relative contribution of vapor-liquid-solid incorporation is increased for higher Be flux, resulting in axial dopant gradients that depend on the nominal doping level.
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Affiliation(s)
- Marcelo Rizzo Piton
- Physics Department, Federal University of São Carlos, São Carlos-SP, Brazil. Optoelectronics Research Centre, Physics Unit, Tampere University, Tampere, Finland
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Ghisalberti L, Potts H, Friedl M, Zamani M, Güniat L, Tütüncüoglu G, Carter WC, Morral AFI. Questioning liquid droplet stability on nanowire tips: from theory to experiment. NANOTECHNOLOGY 2019; 30:285604. [PMID: 30916044 DOI: 10.1088/1361-6528/ab139c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Liquid droplets sitting on nanowire (NW) tips constitute the starting point of the vapor-liquid-solid method of NW growth. Shape and volume of the droplet have been linked to a variety of growth phenomena ranging from the modification of growth direction, NW orientation, crystal phase, and even polarity. In this work we focus on numerical and theoretical analysis of the stability of liquid droplets on NW tips, explaining the peculiarity of this condition with respect to the wetting of planar surfaces. We highlight the role of droplet pinning at the tip in engineering the contact angle. Experimental results on the characteristics of In droplets of variable volume sitting on the tips or side facets of InAs NWs are also provided. This work contributes to the fundamental understanding of the nature of droplets contact angle at the tip of NWs and to the improvement of the engineering of such nanostructures.
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Affiliation(s)
- Lea Ghisalberti
- Laboratoire des Matériaux Semiconducteurs, Institut des Matériaux, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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Demonstration of extrinsic chirality of photoluminescence with semiconductor-metal hybrid nanowires. Sci Rep 2019; 9:5040. [PMID: 30911080 PMCID: PMC6434037 DOI: 10.1038/s41598-019-41615-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 03/08/2019] [Indexed: 11/24/2022] Open
Abstract
Chiral optical response is an inherent property of molecules and nanostructures, which cannot be superimposed on their mirror images. In specific cases, optical chirality can be observed also for symmetric structures. This so-called extrinsic chirality requires that the mirror symmetry is broken by the geometry of the structure together with the incident or emission angle of light. From the fabrication point of view, the benefit of extrinsic chirality is that there is no need to induce structural chirality at nanoscale. This paper reports demonstration extrinsic chirality of photoluminescence emission from asymmetrically Au-coated GaAs-AlGaAs-GaAs core-shell nanowires fabricated on silicon by a completely lithography-free self-assembled method. In particular, the extrinsic chirality of PL emission is shown to originate from a strong symmetry breaking of fundamental HE11 waveguide modes due to the presence of the asymmetric Au coating, causing preferential emission of left and right-handed emissions in different directions in the far field.
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9
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Koivusalo ES, Hakkarainen TV, Galeti HVA, Gobato YG, Dubrovskii VG, Guina MD. Deterministic Switching of the Growth Direction of Self-Catalyzed GaAs Nanowires. NANO LETTERS 2019; 19:82-89. [PMID: 30537843 DOI: 10.1021/acs.nanolett.8b03365] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The typical vapor-liquid-solid growth of nanowires is restricted to a vertical one-dimensional geometry, while there is a broad interest for more complex structures in the context of electronics and photonics applications. Controllable switching of the nanowire growth direction opens up new horizons in the bottom-up engineering of self-assembled nanostructures, for example, to fabricate interconnected nanowires used for quantum transport measurements. In this work, we demonstrate a robust and highly controllable method for deterministic switching of the growth direction of self-catalyzed GaAs nanowires. The method is based on the modification of the droplet-nanowire interface in the annealing stage without any fluxes and subsequent growth in the horizontal direction by a twin-mediated mechanism with indications of a novel type of interface oscillations. A 100% yield of switching the nanowire growth direction from vertical to horizontal is achieved by systematically optimizing the growth parameters. A kinetic model describing the competition of different interface structures is introduced to explain the switching mechanism and the related nanowire geometries. The model also predicts that the growth of similar structures is possible for all vapor-liquid-solid nanowires with commonly observed truncated facets at the growth interface.
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Affiliation(s)
- Eero S Koivusalo
- Optoelectronics Research Centre , Tampere University of Technology , P.O. Box 692, Tampere 33101 , Finland
| | - Teemu V Hakkarainen
- Optoelectronics Research Centre , Tampere University of Technology , P.O. Box 692, Tampere 33101 , Finland
| | - Helder V A Galeti
- Electrical Engineering Department , Federal University of São Carlos , São Carlos , São Paulo 13565-905 , Brazil
| | - Yara G Gobato
- Physics Department , Federal University of São Carlos , São Carlos , São Paulo 13565-905 , Brazil
| | | | - Mircea D Guina
- Optoelectronics Research Centre , Tampere University of Technology , P.O. Box 692, Tampere 33101 , Finland
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Tauchnitz T, Berdnikov Y, Dubrovskii VG, Schneider H, Helm M, Dimakis E. A simple route to synchronized nucleation of self-catalyzed GaAs nanowires on silicon for sub-Poissonian length distributions. NANOTECHNOLOGY 2018; 29:504004. [PMID: 30240362 DOI: 10.1088/1361-6528/aae361] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We demonstrate a simple route to grow ensembles of self-catalyzed GaAs nanowires with a remarkably narrow statistical distribution of lengths on natively oxidized Si(111) substrates. The fitting of the nanowire length distribution (LD) with a theoretical model reveals that the key requirements for narrow LDs are the synchronized nucleation of all nanowires on the substrate and the absence of beam shadowing from adjacent nanowires. Both requirements are fulfilled by controlling the size and number density of the openings in SiO x , where the nanowires nucleate. This is achieved by using a pre-growth treatment of the substrate with Ga droplets and two annealing cycles. The narrowest nanowire LDs are markedly sub-Poissonian, which validates the theoretical predictions about temporally anti-correlated nucleation events in individual nanowires, the so-called nucleation antibunching. Finally, the reproducibility of sub-Poissonian LDs attests the reliability of our growth method.
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Affiliation(s)
- Tina Tauchnitz
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany. Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, D-01062 Dresden, Germany
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Koivusalo ES, Hakkarainen TV, Guina MD, Dubrovskii VG. Sub-Poissonian Narrowing of Length Distributions Realized in Ga-Catalyzed GaAs Nanowires. NANO LETTERS 2017; 17:5350-5355. [PMID: 28782958 DOI: 10.1021/acs.nanolett.7b01766] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Herein, we present experimental data on the record length uniformity within the ensembles of semiconductor nanowires. The length distributions of Ga-catalyzed GaAs nanowires obtained by cost-effective lithography-free technique on silicon substrates systematically feature a pronounced sub-Poissonian character. For example, nanowires with the mean length ⟨L⟩ of 2480 nm show a length distribution variance of only 367 nm2, which is more than twice smaller than the Poisson variance h⟨L⟩ of 808 nm2 for this mean length (with h = 0.326 nm as the height of GaAs monolayer). For 5125 nm mean length, the measured variance is 1200 nm2 against 1671 nm2 for Poisson distribution. A supporting model to explain the experimental findings is proposed. We speculate that the fluctuation-induced broadening of the length distribution is suppressed by nucleation antibunching, the effect which is commonly observed in individual vapor-liquid-solid nanowires but has never been seen for their ensembles. Without kinetic fluctuations, the two remaining effects contributing to the length distribution width are the nucleation randomness for nanowires emerging from the substrate and the shadowing effect on long enough nanowires. This explains an interesting time evolution of the variance that saturates after a short incubation stage but then starts increasing again due to shadowing, remaining, however, smaller than the Poisson value for a sufficiently long time.
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Affiliation(s)
- Eero S Koivusalo
- Optoelectronics Research Centre, Tampere University of Technology , Korkeakoulunkatu 3, FI 33720 Tampere, Finland
| | - Teemu V Hakkarainen
- Optoelectronics Research Centre, Tampere University of Technology , Korkeakoulunkatu 3, FI 33720 Tampere, Finland
| | - Mircea D Guina
- Optoelectronics Research Centre, Tampere University of Technology , Korkeakoulunkatu 3, FI 33720 Tampere, Finland
| | - Vladimir G Dubrovskii
- ITMO University , Kronverkskiy pr. 49, 197101 St. Petersburg, Russia
- St. Petersburg Academic University , Khlopina 8/3, 194021 St. Petersburg, Russia
- Ioffe Physical Technical Institute of the Russian Academy of Sciences , Politekhnicheskaya 26, 194021 St. Petersburg, Russia
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