A5013867946- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- ZnO doping and properties
- Quantum Dots Synthesis And Properties
- Chalcogenide Semiconductor Thin Films
- Metal and Thin Film Mechanics
- Acoustic Wave Resonator Technologies
- Linguistics and Discourse Analysis
- Historical Linguistics and Language Studies
- Advanced Semiconductor Detectors and Materials
- Copper-based nanomaterials and applications
- Asymmetric Synthesis and Catalysis
- Inorganic and Organometallic Chemistry
- Synthesis and Reactions of Organic Compounds
- American Constitutional Law and Politics
- Semiconductor materials and interfaces
- Synthesis of Organic Compounds
- Photocathodes and Microchannel Plates
- Chemical Synthesis and Analysis
- Semiconductor Lasers and Optical Devices
- Synthesis and Reactivity of Sulfur-Containing Compounds
- Photonic and Optical Devices
- Quantum and electron transport phenomena
University of Strathclyde
2016-2025
Scottish Universities Physics Alliance
1995-2025
Inspira Medical Center Woodbury
2024
DEVCOM Army Research Laboratory
2022-2023
Humboldt-Universität zu Berlin
2022-2023
Rowan University
2023
University of Duisburg-Essen
2023
Advocate Illinois Masonic Medical Center
2023
University of Liverpool
2012-2023
National Institute for Materials Science
2023
We report the first direct observation of phase decomposition in a luminescent alloy and show that this decomposition, allied to quantum confinement enhancements, accounts for surprisingly high efficiency InGaN-based diodes manufactured by Nichia Chemical Industries. Hence nanostructure, rather than composition, is responsible success these devices. A common form nearly pure InN dots, occurs across large range average indium content InGaN leads universal scalability optical spectra.
Solid state UV emitters have many advantages over conventional sources. The (Al,In,Ga)N material system is best suited to produce LEDs and laser diodes from 400 nm down 210 nm—due its large tuneable direct band gap, n- p-doping capability up the largest bandgap AlN a growth fabrication technology compatible with current visible InGaN-based LED production. However AlGaN based UV-emitters still suffer numerous challenges compared their counterparts that become most obvious by consideration of...
We report a comparative study of the emission and absorption spectra range commercial InGaN light-emitting diodes high-quality epilayers. A working definition form edge for alloys is proposed, which allows unique Stokes’ shift. linear dependence shift on peak energy then demonstrated using experimental both diode epilayer samples, supplemented by data from literature. In addition, broadening shown to increase as decreases. These results are discussed in terms localization excitons at highly...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRapid Colorimetric Estimation of PhenolR. W. MartinCite this: Anal. Chem. 1949, 21, 11, 1419–1420Publication Date (Print):November 14, 1949Publication History Published online1 May 2002Published inissue 14 November 1949https://doi.org/10.1021/ac60035a038RIGHTS & PERMISSIONSArticle Views740Altmetric-Citations101LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum full text article downloads since 2008 (both PDF and HTML) across all...
A novel BODIPY-containing organic small molecule is synthesized and employed as a down-converting layer on commercial blue light-emitting diode (LED). The resulting hybrid device demonstrates white-light emission under low-current operation, with color coordinates of (0.34, 0.31) an efficacy 13.6 lm/W; four times greater than the parent LED.
The search for efficient but inexpensive photovoltaics over the past decade has been disrupted by advent of lead-halide perovskite solar cells. Despite impressive rises in performance, toxicity and stability concerns these materials have prompted a broad, interdisciplinary community across world to lead-free stable alternatives. A set such that recently gained attention are semiconductors CuI–AgI–BiI 3 phase space their derivatives. These include ternary silver bismuth iodide compounds (Ag...
A systematic investigation of the optical properties β‐, α‐, and κ‐phase gallium oxide (Ga 2 O 3 ) polymorphs is conducted by UV–vis spectrophotometry through Swanepoel method temperature‐dependent photoluminescence. Using same approach apparatus allows similarities differences between these three phases to be directly established. Differences are observed, including refractive indices 1.89 (β), 2.00 (α), 1.85 (κ) bandgaps 4.99 eV 5.32 4.87 (κ). In luminescence studies, four emission peaks...
Micro-light emitting diode (LED) arrays with diameters of 4 to 20 μm have been fabricated and were found be much more efficient light emitters compared their broad-area counterparts, up five times enhancement in optical power densities. The possible mechanisms responsible for the improvement performance investigated. Strain relaxation microstructures as measured by Raman spectroscopy was not observed, arguing against theories an increase internal quantum efficiency due a reduction...
Monte Carlo simulations of anomalous ion channeling in near-lattice-matched $\mathrm{AlInN}/\mathrm{GaN}$ bilayers allow an accurate determination the strain state AlInN by Rutherford backscattering or channeling. Although these estimates agree well with x-ray diffraction (XRD) results, XRD composition are shown to have limited accuracy, due a possible deviation from Vegard's law, which we quantify for this alloy. As InN fraction increases 13% 19%, films changes tensile compressive lattice...
We identify a dominant light-emitting center in ion-implanted $\text{GaN}:{\text{Eu}}^{3+}$ for which the lattice damage has been completely healed, according to x-ray diffraction and Rutherford backscattering spectrometry measurements, by high-temperature, high-pressure annealing. This is likely be isolated substitutional ${\text{Eu}}_{\text{Ga}}$ defect. It lacks ``subgap'' excitation band therefore no state GaN gap, shows threefold splitting of its ${^{7}\text{F}}_{2}$ level, with two...
Cu2ZnSnSe4 thin films, fabricated on bare or molybdenum coated glass substrates by magnetron sputtering and selenisation, were studied a range of techniques. Photoluminescence spectra reveal an excitonic peak two phonon replicas donor-acceptor pair (DAP) recombination. Its acceptor donor ionisation energies are 27 7 meV, respectively. This demonstrates that high-quality films can be fabricated. An experimental value for the longitudinal optical energy 28 meV was estimated. The band gap 1.01...
We give an overview of the use cathodoluminescence (CL) in scanning electron microscopy (SEM) for nano-scale characterization semiconducting materials and devices. discuss technical aspects measurement, such as factors limiting spatial resolution design considerations efficient collection optics. The advantages more recent developments technique are outlined, including hyperspectral imaging mode combination CL other SEM-based measurements. illustrate these points with examples from our own...
We investigate the effects of V-pits on optical properties a state-of-the-art, highly efficient, blue InGaN/GaN multi-quantum-well (MQW) light-emitting diode (LED) with high internal quantum efficiency (IQE) >80%. The LED is structurally enhanced by incorporating pre-MQW InGaN strain-relief layer low InN content and patterned sapphire substrate. For comparison, conventional (unenhanced) MQW (with an IQE 46%) grown under similar conditions was subjected to same measurements. Scanning...
Abstract A metal-organic hybrid perovskite (CH 3 NH PbI ) with three-dimensional framework of metal-halide octahedra has been reported as a low-cost, solution-processable absorber for thin-film solar cell power-conversion efficiency over 20%. Low-dimensional layered perovskites metal halide slabs separated by the insulating organic layers are to show higher stability, but efficiencies cells limited confinement excitons. In order explore and transport excitons in zero-dimensional...
A new method for the stabilization and manipulation of unstable states a pattern forming system is presented. The technique applied to an optical where homogeneous solutions, rolls, squares, hexagons, honeycombs are all stabilized tracked. control consists small spatial modulation input pump field, which derived from Fourier transform output electric field. Once achieved, vanishes. can be used as numerical tool systems determine existence stability solutions.
Light-emitting diodes (LEDs) based on an interconnected array of GaN/InGaN micro-ring elements have been demonstrated. The devices electrical characteristics similar to those conventional broad-area devices. However, due the large surface areas provided by sidewalls, extraction efficiency is greatly enhanced. Intense light emission at periphery micro-rings observed upon excitation electron beam, suggesting scattering photons which are extracted through sidewalls. provide a doubling in total...
We present Raman-scattering measurements on InxGa1−xN over the entire composition range of alloy. The frequencies A1(LO) and E2 modes are reported show a good agreement with one-mode behavior dispersion predicted by modified random-element isodisplacement model. mode displays high intensity relative to due resonant enhancement. For above band-gap excitation, peak frequency shifts as function excitation energy selective regions different In contents, strong multiphonon scattering up 3LO is...
The intensity of Eu-related luminescence from ion-implanted GaN with a 10nm thick AlN cap, both grown epitaxially by metal organic chemical vapor deposition (MOCVD) is increased markedly high-temperature annealing at 1300°C. Photoluminescence (PL) and PL excitation (PLE) studies reveal variety Eu centers different mechanisms. High-resolution spectra low temperature clearly show that emission lines ascribed to D05-F27 (∼622nm), D05-F37 (∼664nm), D05-F17 (∼602nm) transitions each consist...
InGaN/GaN multiple quantum wells (MQWs) have been studied by using cathodoluminescence hyperspectral imaging with high spatial resolution. Variations in peak emission energies and intensities across trenchlike features V-pits on the surface of MQWs are investigated. The MQW from region inside is redshifted approximately 45 meV more intense than surrounding planar regions sample, whereas blueshifted about 20 relatively weaker. By employing this technique to nanostructures it possible...
Abstract Hyperspectral cathodoluminescence imaging provides spectrally and spatially resolved information on luminescent materials within a single dataset. Pushing the technique toward its ultimate nanoscale spatial limit, while at same time dispersing collected light before detection, increases challenge of generating low-noise images. This article describes aspects instrumentation, in particular data treatment methods, which address this problem. The methods are demonstrated by applying...
GaN/AlGaN multiple quantum wells (MQWs) are grown on a 2¯01-oriented β-Ga2O3 substrate. The optical and structural characteristics of the MQW structure compared with those similar sapphire. Scanning transmission electron microscopy atomic force images show that exhibits higher crystalline quality well-defined when to X-ray diffraction rocking curve photoluminescence excitation analyses confirm lower density dislocation defects in sample A detailed analysis time-integrated time-resolved...
A guanidinium incorporated double cation mixed halide perovskite was investigated by including bromide (GABr) in methylammonium lead iodide (MAPI) under various GABr concentrations. The XRD patterns with characteristic (1 1 0), (2 2 0) and (3 peaks showed an initial shift towards lower angles then higher angles, indicating lattice expansion contraction increasing content. Increasing the concentration above 10% resulted reducing visible absorbance of compound along widening bandgap. bandgap...