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We report on individual-InAs nanowire optoelectronic devices which, through surface-state engineering, can be tailored to exhibit either negative- or positive-photoconductivity, opening pathways towards engineering semiconductor nanowires for novel optical-memory and photodetector applications.
Nanowires show unique promise for a multitude of optoelectronic devices, ranging from solar cells to terahertz (THz) photonic devices. Here, we discuss how THz spectroscopy is guiding the development of such nanowire-based devices. As an example, we focus on developing nanowire-based THz polarization modulators.
We fabricate AlGaAs nanoantennas on a glass substrate and demonstrate the highest nonlinear conversion efficiency of 10−4 with the capability for shaping the radiation patterns and polarization of the second harmonic emission in both forward and backward directions. We also decode dynamic multipolar contributions to the second harmonic generation within such nanoantennas.
Accurate positioning of semiconductor nanowires with lasing emission at room temperature at targeted locations, onto multiple substrates and forming complex spatial patterns is demonstrated using a novel nanoscale Transfer Printing technique.
The high refractive index of III-V semiconductors results in strong waveguiding of light in nanowires, despite their small cross-section dimensions. We will discuss how these waveguiding properties can be used to design nanowire lasers and solar cells with functionalities not possible in conventional, planar devices.
Electrical contacts between metals and semiconductors are fundamentally important for practical semiconductor devices. This work reports the electrical characterization of nanowire arrays fabricated by a top-down approach, where electron beam lithography (EBL) and a highly anisotropic Cl2/H2/Ar inductively coupled plasma (ICP) reactive ion etching (RIE) is utilised to generate vertical arrays of InP...
By combining Finite-Difference-Time-Domain simulations and the detailed-balance model of solar cell, we study how absorption efficiency determines the short circuit current density, Jsc, of single vertical nanowire (NW) solar cells. We find that due to the very high absorption efficiency, vertical NW delivers Jsc that are one order of magnitude higher than planar solar cells.
InP-InxGa(1-x)As-InP quantum well tube (QWT) structures are grown on InP nanowires that are [100] oriented. The In mole fraction, x is varied between 0 and 1. The QWTs grown on the facets of the [100] nanowires that have {100} and {011} side facets forming an octagonal cross-section, are found to be highly non-uniform. Bright emission is observed at room temperature from these QWTs. Band-gap tunability...
Ths active region position in broad-waveguide lasers can significantly influence the performance of the device due to significant differences in mobility between electrons and holes. An increase in output power by 25% was observed in lasers with the active region positioned close to the p-cladding layer.
ZnTe:O highly mismatched alloys have been produced by isoelectric oxygen implantation into ZnTe and the micro structural and optical properties of ZnTe:O materials have been investigated in detail. The proper dose of oxygen ions led to the formation of intermediate band located at the energy level of ∼0.45eV below the conduction band while high dose of oxygen ions caused an amorphous ZnTe surface...
InP nanowire arrays have been grown and optimized using selective area epitaxy by metalorganic chemical vapour deposition technique. High quality stacking fault free wurtzite nanowires with a wide range of diameters and room temperature minority carrier lifetime as high as ∼ 1.6 ns have been obtained. An axially doped n-i-p structure was further grown and successfully fabricated into solar cell devices...
We report a post-growth approach to increase the radiative recombination efficiency of GaAs nanowires, beyond what has been achieved using surface passivation. This is done by coupling the nanowires to resonant plasmonic nanocavities to reduce the radiative recombination lifetime of minority carriers, thereby increasing the radiative efficiency by an order of magnitude.
We have studied the electronic transport characteristics of nanowire field effect transistors (NWFETs) made from phase-pure wurtzite (WZ) and zinc blende (ZB) InAs nanowires (NWs). The electronic characteristics were obtained at temperatures between 4 and 300 K. The ZB NWFETs exhibited a greater sensitivity to the surrounding atmosphere than WZ NWFETs. The WZ NWFETs had a higher mobility than ZB NWFETs...
III-V semiconductor nanowires are promising for optoelectronic device applications. Applications of GaAs nanowires however have been limited due to low quantum/radiative efficiency. We discuss two approaches to increase the quantum efficiency of (Al) GaAs nanowires.
Semiconductor nanowires grown via the vapour-liquid-solid (VLS) mechanism are promising for miniaturisation of optoelectronic devices. Efficient optoelectronic devices require these nanowires to have high quantum efficiency. While optimizing the growth process to eliminate bulk defects and achieve perfect surface passivation is one approach to increase the quantum efficiency of nanowires1, coupling...
III–V semiconductor nanowires hold outstanding potential as key component for future photonic and electronic devices, among which GaAs/AlGaAs heterostructure nanowires wires show particular promise. However, due to the large surface-to-volume ratio, the carrier lifetime and mobility of GaAs nanowires are extremely sensitive to the surface/interface states. Although nearly intrinsic exciton lifetimes...
We review various III-V compound semiconductor nanowires grown by MOCVD, mainly focusing on their phase control, optical and structural properties and some prototype optoelectronic devices based on these nanowires including solar cells and lasers.
Nanoparticles are rapidly becoming ubiquitous in modern technology and so there is an emerging need to characterise single nanoparticles rapidly and accurately. In the current technological paradigm, non-optical techniques such as electron microscopy (EM) and atomic-force microscopy (AFM) are favored for this role. Nano-characterization using optical microscopy though has several advantages; it can...
The growth of III-V semiconductor core-shell nanowires by Au-catalyzed metal organic chemical vapor deposition is described. The effect of growth conditions on the properties of the nanowires is discussed. Results nanowire solar cells and lasers are also presented.
In this work a transient grating experiment was used to explore the inplane transport properties and two-colour pump-probe and time resolved photolu-minescence experiments were used to explore the population dynamics of excitons in ZnO quantum wells. By implementing stepped barriers in such quantum wells we also show that the overlap of the electron and hole wavefunctions can be controlled.
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