Ray LaPierre

McMaster University

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Nebile Işık Göktaş

McMaster University

Chris Haapamaki

McMaster University

ВГ

В. Г. Дубровский

St Petersburg University

P Kuyanov

McMaster University

A. C. E. Chia

McMaster University

Jonathan Boulanger

Harvard University

Jonathan Baugh

University of Waterloo

Yu. A. Pusep

Universidade de São Paulo

B. J. Robinson

Cardiff Metropolitan University

Gregory W. Holloway

University of Oxford

Cooperative Institutions

McMaster University

Centre National de la Recherche Scientifique

University of Waterloo

Universidade Federal de São Carlos

Universidade de São Paulo

Institut Pascal

Université Clermont Auvergne

Sigma Clermont

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Technical University of Denmark

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(Invited) Gap Nanowires with Twinning Superlattices: Structure, Optical Properties and Applications

Meeting abstracts/Meeting abstracts (Electrochemical Society. CD-ROM) (2020)

Nebile Işık Göktaş Divyanshu Gupta Oleg Rubel Ray LaPierre

Semiconductor nanowires (NWs) are a good candidate for future optoelectronic devices. However, the control of the essential parameters that determine the electronic and optical quality of NWs, such as crystal structure and incorporation of impurity dopants, are still challenging problems. Most III-V NWs exhibit crystal defects, which are typically randomly distributed zincblende twinning segments and stacking faults that can affect the optical and electrical properties of NW devices. The incorporation of intentional impurity dopants in NWs is important for the fabrication of p-n junctions and control of the electrical conductivity of NWs. The effect of Te and Be impurity dopant concentration on the crystal structure, surface roughness and optical properties of GaAs NWs will be presented. Four identical GaAs NW arrays were grown: an undoped sample (as a reference) and 6 samples with different Te and Be doping concentration. High resolution transmission electron microscopy (HRTEM) revealed an unusual superlattice twinning, with periodicity that became wider and more regular as the doping level increased. Twin boundaries in GaP are shown to act as an atomically narrow plane of wurtzite phase with a type-I homostructure band alignment. Twin boundaries and stacking faults (wider regions of the wurtzite phase) lead to the introduction of shallow trap states observed in photoluminescence studies. Controlling the surface roughness, the periodicity, and the width of twinning planes with doping concentration might open new possibilities for high efficiency NW-based thermoelectric devices, but also has wide implications for all NW devices.

Wurtzite crystal structure

Crystal (programming language)

10.1149/ma2020-01161076mtgabs

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Nanowires for energy: A review

Applied Physics Reviews (2018)

Nebile Işık Göktaş Paul Wilson Ara Ghukasyan Devan Wagner Simon McNamee

Semiconductor nanowires (NWs) represent a new class of materials and a shift from conventional two-dimensional bulk thin films to three-dimensional devices. Unlike thin film technology, lattice mismatch strain in NWs can be relaxed elastically at the NW free surface without dislocations. This capability can be used to grow unique heterostructures and to grow III-V NWs directly on inexpensive substrates, such as Si, rather than lattice-matched but more expensive III-V substrates. This capability, along with other unique properties (quantum confinement and light trapping), makes NWs of great interest for next generation optoelectronic devices with improved performance, new functionalities, and reduced cost. One of the many applications of NWs includes energy conversion. This review will outline applications of NWs in photovoltaics, thermoelectrics, and betavoltaics (direct conversion of solar, thermal, and nuclear energy, respectively, into electrical energy) with an emphasis on III-V materials. By transitioning away from bulk semiconductor thin films or wafers, high efficiency photovoltaic cells comprised of III-V NWs grown on Si would improve performance and take advantage of cheaper materials, larger wafer sizes, and improved economies of scale associated with the mature Si industry. The thermoelectric effect enables a conversion of heat into electrical power via the Seebeck effect. NWs present an opportunity to increase the figure of merit (ZT) of thermoelectric devices by decreasing the thermal conductivity (κ) due to surface phonon backscattering from the NW surface boundaries. Quantum confinement in sufficiently thin NWs can also increase the Seebeck coefficient by modification of the electronic density of states. Prospects for III-V NWs in thermoelectric devices, including solar thermoelectric generators, are discussed. Finally, betavoltaics refers to the direct generation of electrical power in a semiconductor from a radioactive source. This betavoltaic process is similar to photovoltaics in which photon energy is converted to electrical energy. In betavoltaics, however, energetic electrons (beta particles) are used instead of photons to create electron-hole pairs in the semiconductor by impact ionization. NWs offer the opportunity for improved beta capture efficiency by almost completely surrounding the radioisotope with semiconductor material. Improving the efficiency is important in betavoltaic design because of the high cost of materials and manufacturing, regulatory restrictions on the amount of radioactive material used, and the enabling of new applications with higher power requirements.

Figure of Merit

10.1063/1.5054842

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Citations (108)

Photoluminescence model of sulfur passivated p-InP nanowires

Nanotechnology (2012)

Naser Tajik Chris Haapamaki Ray LaPierre

The effect of ammonium polysulfide solution, (NH4)2Sx, on the surface passivation of p-doped InP nanowires (NWs) was investigated by micro-photoluminescence. An improvement in photoluminescence (PL) intensity from individual NWs upon passivation was used to optimize the passivation procedure using different solvents, sulfur concentrations and durations of passivation. The optimized passivation procedure gave an average of 24 times improvement in peak PL intensity. A numerical model is presented to explain the PL improvement upon passivation in terms of a reduction in surface trap density by two orders of magnitude from 1012 to 1010 cm−2, corresponding to a change in surface recombination velocity from 106 to 104 cm s−1. The diameter dependence of the PL intensity is investigated and explained by the model. The PL intensity from passivated nanowires decreased to its initial (pre-passivation) value over a period of seven days in ambient air, indicating that the S passivation was unstable.

Passivation

Intensity

10.1088/0957-4484/23/31/315703

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Citations (42)

Magnetic field driven interminiband charge transfer in InGaAs/InP superlattices

Journal of Physics Condensed Matter (2015)

Yu. A. Pusep Bruno G. Tavares M. A. T. Patricio L. Fernandes dos Santos Ray LaPierre

The characteristic energies, occupancies and polarizations of the minibands formed by the Γ-Γ and Γ-Xz interlayer electon tunnelings in the InGaAs/InP superlattices are studied in the regime of the integer quantum Hall effect by polarization resolved photoluminescence. Accordingly, the magnetic field induced shrinkage of the interminiband gap, predicted by the theory, and as a consequence, the redistribution of charge over the superlattice minibands and the depolarization of the quantum Hall electron states are observed at odd filling factors. The response of the electrons residing in the InGaAs/InP superlattice minibands to the magnetic field is found very similar to the corresponding response of the electrons confined in the symmetric and anti-symmetric two-dimensional minibands of GaAs/AlGaAs double quantum wells. The presented results are evidence of the formation of the correlated states in multi-component electron systems formed in semiconductor multiple layers at odd filling factors.

10.1088/0953-8984/27/24/245601

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Effect of the plasma etching on InAsP/InP quantum well structures measured through low temperature micro-photoluminescence and cathodoluminescence

HAL (Le Centre pour la Communication Scientifique Directe) (2020)

Jean-Pierre Landesman Nebile Işık Göktaş Ray LaPierre Shahram Ghanad-Tavakoli E. Pargon

Cathodoluminescence

Plasma Etching

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Multi-spectral optical absorption in substrate-free nanowire arrays

Applied Physics Letters (2014)

Junpeng Zhang Navneet Dhindsa A. C. E. Chia Jonathan Boulanger Iman Khodadad

A method is presented of fabricating gallium arsenide (GaAs) nanowire arrays of controlled diameter and period by reactive ion etching of a GaAs substrate containing an indium gallium arsenide (InGaP) etch stop layer, allowing the precise nanowire length to be controlled. The substrate is subsequently removed by selective etching, using the same InGaP etch stop layer, to create a substrate-free GaAs nanowire array. The optical absorptance of the nanowire array was then directly measured without absorption from a substrate. We directly observe absorptance spectra that can be tuned by the nanowire diameter, as explained with rigorous coupled wave analysis. These results illustrate strong optical absorption suitable for nanowire-based solar cells and multi-spectral absorption for wavelength discriminating photodetectors. The solar-weighted absorptance above the bandgap of GaAs was 94% for a nanowire surface coverage of only 15%.

Absorptance

Indium arsenide

Indium gallium arsenide

10.1063/1.4896772

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Citations (13)

Integrated III-V/Si Visible and IR Nanowire Photodetectors

APS March Meeting Abstracts (2019)

Arjun Shetty Eduardo Barrera F. Sfigakis Mitchell Robson Nebile Isik

Visible spectrum

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Photoluminescence model for a hybrid aptamer-GaAs optical biosensor

Journal of Applied Physics (2010)

H. A. Budz M. Monsur Ali Yishuang Li Ray LaPierre

The present work describes the development of a hybrid GaAs-aptamers biosensor for the label-free detection of adenosine 5′-triphosphate (ATP). The implemented sensing strategy relies on the sensitivity of the GaAs photoluminescence (PL) emission to the local environment at its surface. Specifically, GaAs substrates were chemically modified with thiol-derivatized oligonucleotide aptamers following conventional condensed-phase deposition techniques and exposed to the target ATP molecules. The resulting modification in the PL intensity is attributed to a specific biorecognition interaction between the aptamer receptors and the ATP target and, more importantly, the accompanying ligand-induced structural change in the aptamer conformation. Since the negatively charged aptamer probes are covalently anchored to the substrate surface, the sensing mechanism can be understood in terms of a change in the surface charge distribution and thereby, the width of the nonemissive GaAs surface depletion layer. Biosensors fabricated with aptamer probes of various lengths indicate a strand length-dependent nature of the luminescence response to the biorecognition events, with longer aptamers yielding a greater PL enhancement. Results provided by several control experiments demonstrate the sensitivity, specificity, and selectivity of the proposed biosensor in accurately identifying ATP. Modeling the performance data by means of Poisson–Boltzmann statistics in combination with the GaAs depletion layer model shows a good correlation between the structural conformation of the aptamers and the PL yield of the underlying substrate. Collectively, the results described within indicate the promise of the prospective luminescence-based GaAs-aptamer biosensor for use in real-time sensing assays requiring a straightforward and efficient means of label-free analytical detection.

Aptamer

10.1063/1.3419714

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Citations (24)

(Invited) Novel Luminescent Materials Based on Semiconductor Nanowires

Meeting abstracts/Meeting abstracts (Electrochemical Society. CD-ROM) (2014)

Ray LaPierre Anders Gustafsson P Kuyanov Chris Haapamaki

We report novel luminescent materials based on group III-V compound semiconductor nanowires. Semiconductor nanowires are essentially one-dimensional rods with length of several microns and diameter below 100 nm. Hence, nanowires exhibit interesting quantum confinement and carrier transport properties. Nanowires are grown using metal seed particles by the vapor-liquid-solid (VLS) process in a molecular beam epitaxy or metalorganic chemical vapor deposition system. By varying the material deposition during growth, axial or radial nanowire heterostructures and p-n junctions may be formed for various device applications including light emitting diodes, lasers, and photodetectors. Due to the large surface area to volume ratio of a nanowire, lattice mismatch strain may be accommodated by elastic distortion of the nanowire without detrimental misfit dislocations, which gives a much greater ability to perform bandgap engineering in nanowires as compared to thin films. Hence, unique heterostructures are possible in nanowires that would be impossible in thin films, opening up new device applications and possibilities in condensed matter physics. We will report our recent work on the photoluminescence properties of InAsP/InP nanowires. InP nanowires were grown on <111> Si substrates by the Au-assisted vapor-liquid-solid process in a gas source molecular beam epitaxy system. InAs y P 1-y segments were grown in the middle of the InP nanowires, creating a multiple quantum dot structure or superlattice. The quantum dot dimensions and composition were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (EDX). Photoluminescence (PL) from the quantum dot structure could be tuned by the InAs y P 1-y composition (y), or by the size of the quantum dot via the quantum confinement effect. Cathodoluminescence (CL) measurements confirmed localized emission from the quantum dots. To reduce detrimental surface states, the nanowires were passivated with an AlInP shell, which resulted in strong PL emission. The growth mechanism of the quantum dots were inferred from the InAsP and InP segment lengths as a function of nanowire diameter. Short InAsP segment lengths were found to grow by depletion of In from the Au particle as well as by direct impingement, while longer segments of InAsP and InP grew by diffusive transport of adatoms from the nanowire sidewalls. The present study offers a manner to engineer the lengths of InAsP quantum dots embedded in InP barriers to better control the PL or CL emission. A novel group III and V gas switching sequence is presented to improve compositional control of the QD.

Vapor–liquid–solid method

10.1149/ma2014-01/42/1564

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Reduction of composition modulation of InGaAsP grown by atomic-hydrogen-assisted epitaxy producing improved double-heterostructure laser performance

Semiconductor Science and Technology (1998)

Ray LaPierre Dylan Thompson B. J. Robinson

InGaAsP laser structures with bandgap wavelengths of 1.15, 1.3 and have been grown on (100) InP substrates by gas source molecular beam epitaxy with and without a simultaneous flux of atomic hydrogen. Broad-area lasers have been fabricated and characterized. Higher threshold current densities and lower slope efficiencies are observed for active region compositions that lie deepest within the miscibility gap and which exhibit greater lateral composition modulation (LCM). The use of atomic-hydrogen-assisted epitaxy is shown to result in improved laser performance and this is attributed to a reduction in the LCM due to the surfactant action of atomic hydrogen.

Modulation (music)

10.1088/0268-1242/13/6/017

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Citations (2)