A5026355943- GaN-based semiconductor devices and materials
- Semiconductor Quantum Structures and Devices
- Metal and Thin Film Mechanics
- Photonic and Optical Devices
- Semiconductor Lasers and Optical Devices
- Optical Coherence Tomography Applications
- Semiconductor materials and devices
- Nanowire Synthesis and Applications
- Acoustic Wave Resonator Technologies
- Ga2O3 and related materials
- Photonic Crystals and Applications
- ZnO doping and properties
- Inorganic Chemistry and Materials
- Optical Coatings and Gratings
- Quantum Information and Cryptography
- Machine Learning in Materials Science
- Advanced Fiber Laser Technologies
- nanoparticles nucleation surface interactions
- Photocathodes and Microchannel Plates
- Advancements in Semiconductor Devices and Circuit Design
- Inorganic Fluorides and Related Compounds
- Quantum and electron transport phenomena
- Advanced Fluorescence Microscopy Techniques
- Metamaterials and Metasurfaces Applications
- Photoacoustic and Ultrasonic Imaging
IMEC
2021-2025
University College Cork
2016-2022
Munster Technological University
2020-2022
KU Leuven
2021
Tyndall Centre
2020
Academy of Scientific and Innovative Research
2014
Central Electronics Engineering Research Institute
2012-2014
Council of Scientific and Industrial Research
2012-2013
Abstract Silicon photonics is a rapidly developing technology that promises to revolutionize the way we communicate, compute, and sense world [1,2,3,4,5,6]. However, lack of highly scalable, native CMOS-integrated light sources one main factors hampering its widespread adoption. Despite significant progress in hybrid heterogeneous integration III-V on silicon [7,8,9,10,11,12], monolithic by direct epitaxial growth materials remains pinnacle realizing cost-effective on-chip sources. Here,...
Abstract We present here a combined experimental and theoretical analysis of the radiative recombination lifetime in ‐plane (11 0) InGaN/GaN quantum dots. The structures have been grown by modified droplet epitaxy time‐resolved photoluminescence measurements performed to gain insight into lifetimes these structures. This is complemented multi‐band calculations. To account for excitonic effects, theory coupled with self‐consistent Hartree Special attention paid impact dot size on results. Our...
Carrier localization effects in III-N heterostructures are often studied the frame of modified continuum-based models utilizing a single-band effective mass approximation. However, there exists no comparison between results continuum model and atomistic calculations on same underlying disordered energy landscape. We present theoretical framework that establishes connection tight-binding theory electronic structure models, here approximation, provide such for (In,Ga)N quantum wells. In our...
In this work, we present a theoretical analysis of the built-in potential, excitonic and biexcitonic properties non-polar InGaN/GaN quantum dots by means self-consistent Hartree calculations using theory. Special attention is paid to impact dot size shape anisotropies on results. Our reveal that even though exhibit strongly reduced fields when compared c-plane dots, are significantly affected these residual fields. Furthermore, changes in field geometrical features modified, result an...
Abstract We report on a combined theoretical and experimental study of the impact alloy fluctuations Coulomb effects electronic optical properties $$c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>c</mml:mi></mml:math> -plane GaN/AlGaN multi-quantum well systems. The presence carrier localization in this system was demonstrated by observations, such as “S-shape” temperature dependence photoluminescence (PL) peak energy, non-exponential PL decay curves that varied across...
Nonclassical light emission, such as entangled and single-photon has attracted significant interest because of its importance in future quantum technology applications. In this work, we study the potential wurtzite (In,Ga)N/GaN dots for novel nonclassical namely, twin-photon emission. Our calculations, based on a fully atomistic many-body framework, reveal that combination carrier localization due to random alloy fluctuations dot, spin–orbit coupling effects, underlying crystal structure,...
We report the successful realisation of intrinsic optical polarisation control by growth, in solid-state quantum dots thermoelectrically cooled temperature regime (≥200 K), using a non-polar InGaN system. With statistically significant experimental data from cryogenic to high temperatures, we show that average degree such system remains constant at around 0.90, below 100 K, and decreases very slowly higher temperatures until reaching 0.77 200 with an unchanged axis determined material...
Abstract We report the direct generation of linearly polarized single photons with a deterministic polarization axis in self-assembled quantum dots (QDs), achieved by use non-polar InGaN without complex device geometry engineering. Here, we present comprehensive investigation properties these QDs and their origin statistically significant experimental data rigorous k · p modeling. The study 180 individual allows us to compute an average degree 0.90, standard deviation only 0.08. When coupled...
In this paper, we have proposed a “Chess board” like photonic crystal (PhC) structure on top surface of p-GaN/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer in conventional LED, n-GaN vertical LED and an embedded PhC for achieving improved light extraction GaN/InGaN LEDs. The results are compared with that the structures 2-D Results from these simulations show maximum having occurs grating period 0.6 μm grating-depth 0.18 ,...
In this work we present a detailed analysis of the second-order piezoelectric effect in wurtzite III-N heterostructures, such as quantum wells and dots, grown on different substrate orientations. Our is based continuum model using here derived analytic expression for polarization vector field function incline angle $\ensuremath{\theta}$ to $c$ axis. This allows straightforward implementation existing well dot codes. calculations systems reveal that especially semipolar structures with high...
In this paper, we have made a clear differentiation among bandgap, diffraction, interference, and refraction effects in photonic crystal structures (PhCs). For observing effects, PhCs are considered on the top p-GaN surface of light emitting diodes (LEDs), whereas for interference effect, hole type to be embedded within n-GaN layer LED. From analysis, it is observed that at particular lattice periodicity, which bandgap lies wavelength interest shows significant extraction due inhibition...
We investigate the atomic scale structure of m-plane InGaN quantum wells grown on bulk GaN templates and reveal that as indium content increases there is an increased tendency for nonrandom clustering atoms to occur. Based atom probe tomography data used this clustering, we develop a k · p model takes these features into account links observed nanostructure optical properties wells. The calculations show electrons holes tend colocalize at clusters. transition energies between electron hole...
Abstract We analyze the potential of c -plane InGaN/GaN quantum dots for polarization entangled photon emission by means an atomistic many-body framework. Special attention is paid to impact random alloy fluctuations on excitonic fine structure and binding energy. Our calculations show that are ideal candidates high temperature as long underlying C 3 v -symmetry preserved. However, when assuming in dot, our reveal while large energies only slightly affected, symmetry basically lost due...
GaN/InGaN based violet light emitting diodes (LEDs), at 430 nm, have been grown on conventional single side polished (SSP) and patterned sapphire substrates (PSS). Characteristics of the epitaxial wafers subsequently fabricated LEDs analyzed. The photoluminescence (PL) peaks observed 428.1 nm 426.1 for layers SSP PSS respectively. PL intensity is 2.9 times higher in case PSS. electroluminescence (EL) 430.78 430.35 output from LED 2.15 than that a forward current 100 mA.
The down conversion of blue to white light with yttrium aluminum garnet (YAG) phosphor is analyzed theoretically for GaN/InGaN emitting diodes. A cerium-doped YAG particle size ∼10 μm having peak emission wavelength 560 nm considered in this study. Effects concentration, thickness the medium, excitation spectrum, and driving current are studied terms luminous efficacy quality emission. It has been observed that above parameters have a significant effect on chromaticity coordinates....
In this work, we present a detailed analysis of the second-order piezoelectric effect in c-plane InxGa1−xN/GaN quantum dots and its consequences for electronic optical properties these systems. Special attention is paid to impact increasing content x on results. We find that general leads an increase electrostatic built-in field. Furthermore, our results show ≥30%, field has significant emission wavelength radiative lifetimes. For instance, at 40% In, lifetime more than doubled when taking...
In this work, we study the impact of second-order piezoelectricity on total built-in field, electronic and optical properties InGaN/GaN quantum dots grown along different crystallographic directions. The calculations are carried out in frame a symmetry-adapted k · p model. Special attention is paid to Coulomb effects (excitonic effects) results. Overall our reveal that for c-plane system with 20% In, piezoelectric secondary importance electron hole wave function overlap. For semi- non-polar...
Silicon photonics is a rapidly developing technology that promises to revolutionize the way we communicate, compute, and sense world. However, lack of highly scalable, native CMOS-integrated light sources one main factors hampering its widespread adoption. Despite significant progress in hybrid heterogeneous integration III-V on silicon, monolithic by direct epitaxial growth materials remains pinnacle realizing cost-effective on-chip sources. Here, report first electrically driven GaAs-based...
Abstract We report on a comprehensive temperature dependent dark current study of high-quality InGaAs/GaAs multi quantum well waveguide photodetectors monolithically integrated silicon. They are through metalorganic vapor-phase selective-area epitaxial growth in 300 mm CMOS pilot line. Defects resulting from the metamorphic III-V devices Si make these susceptible to different leakage mechanisms at higher operating temperatures. For high-temperature operation complex photonics-electronics...
The use of Optical Coherence Tomography in the field clinical diagnosis is significant. There are different types swept source lasers available on market today, however, their design and associated complex fabrication process increase cost. In work presented here, an economical six-section slotted tunable laser operating near 850 nm has been designed fabricated using a UV optical lithography process. monolithically integrable without need for any regrowth step. Initial characterization...
In this paper, we use Finite-Difference Time-Domain(FDTD) method to study light extraction enhancement in GaN-based LEDs. We have proposed a novel Chess-board like photonic crystal structure on top surface of p-GaN/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer conventional LED and n-GaN vertical LED. The results are compared with the structures 2-D (PhC) Results from these simulations show that maximum for occurs grating...
In this work we outline our multiscale approach for modeling electronic, optical and transport properties of III-N-based heterostructures light emitting diodes (LEDs). We discuss framework connecting atomistic tight-binding theory continuum-based calculations how finite element volume meshes are generated purpose. Utilizing present an initial comparison the electronic structure (In,Ga)N quantum well carried out within a single band effective mass approximation. show that virtual crystal...