179 results on '"Judy M Rorison"'
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2. Giant Bowing of the Bandgap and Spin-Orbit Splitting in GaP1-xBix Dilute Bismide Alloys.
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Zoe L. Bushell, Christopher A. Broderick, Lukas Nattermann, Rita Joseph, Joseph L. Keddie, Judy M. Rorison, Kerstin Volz, and Stephen J. Sweeney
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- 2020
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3. Dilute bismide / dilute nitride type ii quantum wells: Novel strain-balanced heterostructures for GaAs-based near- and mid-infrared photonics.
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Christopher A. Broderick, Shirong Jin Jin, Igor P. Marko, Konstanze Hind, Peter Ludewig, Zoe L. Bushell, Wolfgang Stolz, Eoin P. O'Reilly, Kerstin Volz, Stephen J. Sweeney, and Judy M. Rorison
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- 2017
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4. Investigation of novel materials for future communication needs: Quantum dots and highly-mismatched alloys.
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Judy M. Rorison, Christopher A. Broderick, W. Xiong, and Q. Wang
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- 2016
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5. Type-II GaAs1-xBix/GaNyAs1-y 'W' quantum wells for strain-compensated GaAs-based telecom lasers
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Stephen J. Sweeney, Zoe C. M. Davidson, Judy M Rorison, Kerstin Volz, Christopher A. Broderick, and Thilo Hepp
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Materials science ,Strain (chemistry) ,law ,business.industry ,Optoelectronics ,Laser ,business ,Quantum well ,law.invention - Published
- 2021
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6. Strain-balanced GaAs1−xBix/GaNyAs1−y W-type quantum wells for GaAs-based 1.3–1.6 µm lasers
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Stephen J. Sweeney, Judy M Rorison, Christopher A. Broderick, and Zoe C. M. Davidson
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Materials science ,Differential gain ,Auger effect ,business.industry ,Laser ,Epitaxy ,Schrödinger equation ,law.invention ,symbols.namesake ,law ,symbols ,Optoelectronics ,Spontaneous emission ,Electronic band structure ,business ,Quantum well - Abstract
Highly-mismatched alloys constitute a promising approach to extend the operational range of GaAs-based quantum well (QW) lasers to telecom wavelengths. This is challenging using type-I QWs due to the difficulty to incorporate sufficient N or Bi via epitaxial growth. To overcome this, we investigate a novel class of strain-compensated type-II QWs combining electron-confining, tensile strained GaN y As 1−y and hole-confining, compressively strained GaAs 1−x Bi x layers. We systematically analyse the optoelectronic properties of W-type GaAs 1−x Bi x /GaN y As 1−y QWs, and identify paths to optimise their threshold characteristics. Solving the multi-band k•p Schrodinger equation self-consistently with Poisson’s equation highlights the importance of electrostatic confinement in determining the optical and differential gain of these QWs. Our calculations demonstrate that GaAs 1−x Bi x /GaN y As 1−y QWs offer broad scope for band structure engineering, with W-type structures presenting the possibility to combine high long-wavelength gain with the intrinsically low non-radiative Auger recombination rates of type-II QWs.
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- 2021
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7. Impact of realistic energy levels on the efficiency of intermediate Band Solar Cells: Impact of carrier loss.
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Qiao-Yi Wang and Judy M. Rorison
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- 2015
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8. Giant Bowing of the Bandgap and Spin-Orbit Splitting in GaP1-xBix Dilute Bismide Alloys
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Christopher A. Broderick, Joseph L. Keddie, Kerstin Volz, Rita Joseph, Stephen J. Sweeney, Judy M Rorison, L. Nattermann, and Zoe L. Bushell
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Electronegativity ,Materials science ,Condensed matter physics ,Spintronics ,chemistry ,Band gap ,Covalent radius ,Energy level splitting ,chemistry.chemical_element ,Coupling (probability) ,Semiconductor laser theory ,Bismuth - Abstract
Highly-mismatched III-V semiconductor alloys containing dilute concentrations of bismuth (Bi) have attracted significant attention in recent years since their unique electronic properties open up a range of possibilities for practical applications in semiconductor lasers, photovoltaics, spintronics, photodiodes, and thermoelectrics. Research on dilute bismide alloys has primarily focused to date on $\text{GaAs}_{1-x}\text{Bi}_{x}$ , where incorporation of Bi brings about a strong reduction of the direct $\Gamma$ -point band gap ( $E_{g}{}^{\Gamma}$ ) –by up to 90 meV per % Bi at low Bi compositions $x$ –characterised by strong, composition-dependent bowing. This unusual behaviour derives from the large differences in size (covalent radius) and chemical properties (electronegativity) between As and Bi.Bi, being significantly larger and more electropositive than As, acts as an isovalent impurity which primarily impacts and strongly perturbs the valence band (VB) structure. This is in contrast to dilute nitride alloys, in which small electronegative nitrogen (N) atoms strongly perturb the conduction band (CB) structure in $\text{GaN}_{x}\text{As}_{1-x}$ and related alloys. Additionally, Bi, being the largest stable group-V element, has strong relativistic (spin-orbit coupling) effects. As such, the reduction of $E_{g}{}^{\Gamma}$ in $(\text{In})\text{GaAs}_{1-x}\text{Bi}_{x}$ is accompanied by a strong increase in the VB spin-orbit splitting energy ( $\Delta_{\text{SO}}$ ).
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- 2020
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9. Highly mismatched III–V semiconductor alloys applied in multiple quantum well photovoltaics
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Judy M Rorison, Christopher A. Broderick, and Wanshu Xiong
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Materials science ,Band gap ,business.industry ,chemistry.chemical_element ,Heterojunction ,02 engineering and technology ,Nitride ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Bismuth ,Gallium arsenide ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Photovoltaics ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,010306 general physics ,0210 nano-technology ,business ,Electronic band structure - Abstract
Adding dilute concentrations of nitrogen (N) or bismuth (Bi) into conventional III-V semiconductor alloys causes a large bowing of the bandgap energy due to the modification of the electronic band structure. This behaviour has attracted significant interest due to the resulting optical and electronic properties. Firstly, the authors present theoretical band structure models for GaAs-based dilute nitride, dilute bismide and dilute bismide-nitride alloys and then use them within current continuity equations to show the photovoltaic behaviour. To describe the band structures of these highly mismatched III-V semiconductor alloys, the authors introduce a 10-, 12- and 14-band k · p Hamiltonian for dilute nitride, dilute bismide and dilute bismide-nitride semiconductors, respectively. The authors then use this approach to analyse GaBiAs multi-quantum well p-i-n structures for photovoltaic performance. Through theoretical analysis the authors can: (i) elucidate important trends in the properties and photovoltaic performance of GaBiAs QW structures and (ii) comment generally on the suitability of GaBiAs alloys and heterostructures for applications in multi-junction solar cells. In particular, the authors identify and quantify the limitations associated with current GaBiAs solar cells, and describe the improvements in performance that can be expected pending further development of this emerging class of devices.
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- 2018
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10. Giant bowing of the band gap and spin-orbit splitting energy in GaP1−xBix dilute bismide alloys
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Christopher A. Broderick, Zoe L. Bushell, Joseph L. Keddie, Judy M Rorison, Stephen J. Sweeney, L. Nattermann, Kerstin Volz, and Rita Joseph
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0301 basic medicine ,Electronic properties and materials ,Giant bowing ,GaP1−xBix ,Band gap ,lcsh:Medicine ,Epitaxy ,Article ,03 medical and health sciences ,0302 clinical medicine ,Spectroscopic ellipsometry measurements ,Impurity ,lcsh:Science ,Electronic band structure ,Physics ,Multidisciplinary ,Valence (chemistry) ,Condensed matter physics ,Bowing ,lcsh:R ,Energy level splitting ,030104 developmental biology ,Semiconductors ,lcsh:Q ,Direct and indirect band gaps ,030217 neurology & neurosurgery - Abstract
Using spectroscopic ellipsometry measurements on GaP1−xBix/GaP epitaxial layers up to x = 3.7% we observe a giant bowing of the direct band gap ($${E}_{g}^{{\rm{\Gamma }}}$$ E g Γ ) and valence band spin-orbit splitting energy (ΔSO). $${E}_{g}^{{\rm{\Gamma }}}$$ E g Γ (ΔSO) is measured to decrease (increase) by approximately 200 meV (240 meV) with the incorporation of 1% Bi, corresponding to a greater than fourfold increase in ΔSO in going from GaP to GaP0.99Bi0.01. The evolution of $${E}_{g}^{{\rm{\Gamma }}}$$ E g Γ and ΔSO with x is characterised by strong, composition-dependent bowing. We demonstrate that a simple valence band-anticrossing model, parametrised directly from atomistic supercell calculations, quantitatively describes the measured evolution of $${E}_{g}^{{\rm{\Gamma }}}$$ E g Γ and ΔSO with x. In contrast to the well-studied GaAs1−xBix alloy, in GaP1−xBix substitutional Bi creates localised impurity states lying energetically within the GaP host matrix band gap. This leads to the emergence of an optically active band of Bi-hybridised states, accounting for the overall large bowing of $${E}_{g}^{{\rm{\Gamma }}}$$ E g Γ and ΔSO and in particular for the giant bowing observed for x ≲ 1%. Our analysis provides insight into the action of Bi as an isovalent impurity, and constitutes the first detailed experimental and theoretical analysis of the GaP1−xBix alloy band structure.
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- 2019
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11. Theory and design of In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ mid-infrared semiconductor lasers: type-I quantum wells for emission beyond 3 $\mu$m on InP substrates
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Stephen J. Sweeney, Eoin Patrick O'reilly, Judy M Rorison, Wanshu Xiong, and Christopher A. Broderick
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010302 applied physics ,Condensed Matter - Materials Science ,Materials science ,theoretical modelling ,business.industry ,Mid infrared ,mid-infrared ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,3. Good health ,Electronic, Optical and Magnetic Materials ,Semiconductor laser theory ,dilute bismide alloy ,0103 physical sciences ,Materials Chemistry ,Optoelectronics ,Electrical and Electronic Engineering ,semiconductor laser ,0210 nano-technology ,business ,Quantum well - Abstract
We present a theoretical analysis and optimisation of the properties and performance of mid-infrared semiconductor lasers based on the dilute bismide alloy In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$, grown on conventional (001) InP substrates. The ability to independently vary the epitaxial strain and emission wavelength in this quaternary alloy provides significant scope for band structure engineering. Our calculations demonstrate that structures based on compressively strained In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ quantum wells (QWs) can readily achieve emission wavelengths in the 3 -- 5 $\mu$m range, and that these QWs have large type-I band offsets. As such, these structures have the potential to overcome a number of limitations commonly associated with this application-rich but technologically challenging wavelength range. By considering structures having (i) fixed QW thickness and variable strain, and (ii) fixed strain and variable QW thickness, we quantify key trends in the properties and performance as functions of the alloy composition, structural properties, and emission wavelength, and on this basis identify routes towards the realisation of optimised devices for practical applications. Our analysis suggests that simple laser structures -- incorporating In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ QWs and unstrained ternary In$_{0.53}$Ga$_{0.47}$As barriers -- which are compatible with established epitaxial growth, provide a route to realising InP-based mid-infrared diode lasers., Comment: Submitted version
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- 2018
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12. Model expressions for the spin-orbit interaction and phonon-mediated spin dynamics in quantum dots
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Judy M Rorison and Martin P Vaughan
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Spin dynamics ,Phonon ,Quantum dynamics ,media_common.quotation_subject ,quantum dots ,02 engineering and technology ,01 natural sciences ,Asymmetry ,Quantum mechanics ,0103 physical sciences ,Materials Chemistry ,Electrical and Electronic Engineering ,010306 general physics ,Spin relaxation ,media_common ,spin orbit interaction ,Physics ,Spin–orbit interaction ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,spin relaxation ,Electronic, Optical and Magnetic Materials ,Quantum dot ,0210 nano-technology ,Ground state - Abstract
Model expressions for the spin-orbit interaction (SOI) in a quantum dot are obtained. The resulting form does not neglect cubic terms and allows for a generalized structural inversion asymmetry. We also obtain analytical expressions for the coupling between states for the electron-phonon interaction and use these to derive spin-relaxation rates, which are found to be qualitatively similar to those derived elsewhere in the literature. We find that, due to the inclusion of cubic terms, the Dresselhaus contribution to the ground state spin relaxation disappears for spherical dots. A comparison with previous theory and existing experimental results shows good agreement thereby presenting a clear analytical formalism for future developments. Comparative calculations for potential materials are presented.
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- 2018
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13. Dilute Nitride Alloys
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Christopher A. Broderick, Eoin P. O'Reilly, Masoud Seifikar, and Judy M Rorison
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Materials science ,Metallurgy ,Nitride - Published
- 2017
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14. Dilute bismide / dilute nitride type ii quantum wells: Novel strain-balanced heterostructures for GaAs-based near- and mid-infrared photonics
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K. Hind, Kerstin Volz, Zoe L. Bushell, Wolfgang Stolz, P. Ludewig, Eoin P. O'Reilly, S. R. Jin, S. J. Sweeney, Christopher A. Broderick, Judy M Rorison, and Igor P. Marko
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Diffraction ,Materials science ,Photoluminescence ,business.industry ,Optoelectronics ,Heterojunction ,Nitride ,Photonics ,business ,Epitaxy ,Absorption (electromagnetic radiation) ,Quantum well - Abstract
We demonstrate a new class of GaAs-based type II quantum wells based on the highly mis-matched III–V semiconductor alloys GaAs 1-x Bi x and GaNyAs 1-y . We theoretically quantify and analyse the available design space for the growth of GaAs 1-x Bi x /GaN y As 1-y type II structures on GaAs. Our calculations indicate that, for alloy compositions and layer thicknesses comparable with epitaxial growth, these heterostructures offer optical emission and absorption at wavelengths up to 3 µm as well as the ability to grow strain-balanced structures. We present the results of experimental measurements on a GaAs 1-x Bi x /GaNyAs 1-y (x = 3.3%, y = 6.25%) structure, grown via metal-organic vapor phase epitaxy. X-ray diffraction measurements indicate good structural quality, which is confirmed by the observation of photoluminescence and optical absorption at room temperature. The measured photoluminescence peak wavelength of 1.72 µm, which is in good agreement with theoretical calculations is, to our knowledge, the longest emission wavelength that has been observed to date using a pseudomorphically grown GaAs-based quantum confined heterostructure.
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- 2017
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15. Optical gain in GaAsBi-based quantum-well diode lasers (Conference Presentation)
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Wolfgang Stolz, Stephen J. Sweeney, Christopher A. Broderick, Igor P. Marko, Shirong Jin, Judy M Rorison, P. Ludewig, Kerstin Volz, and Eoin P. O'Reilly
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010302 applied physics ,Materials science ,Band gap ,business.industry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,law.invention ,Semiconductor laser theory ,Optics ,law ,0103 physical sciences ,Optoelectronics ,Semiconductor optical gain ,Spontaneous emission ,0210 nano-technology ,business ,Absorption (electromagnetic radiation) ,Lasing threshold ,Quantum well - Abstract
GaAsBi offers the possibility to develop near-IR semiconductor lasers such that the spin-orbit-split-off energy (ΔSO) is greater than the bandgap (Eg) in the active region with lasing wavelengths in the datacom/telecom range of 1.3-1.6 μm. This promises to suppress the dominant efficiency-limiting loss processes as Auger recombination, involving the generation of “hot” holes in the spin-orbit split-off band (the so-called “CHSH” process), and inter-valence band absorption (IVBA), where emitted photons are re-absorbed in the active region, thereby increasing the internal optical losses and negatively impacting upon the laser characteristics being responsible for the main energy consumption. In addition to growth and fabrication processes refinement, a key aspect of efforts to continue the advancement of the GaAsBi material system for laser applications is to develop a quantitative understanding of the impact of Bi on key device parameters. In this work, we present the first experimental measurements of the absorption, spontaneous emission, and optical gain spectra of GaAsBi/AlGaAs QW lasers using a segmented contact method and a theoretical analysis of these devices, which shows good quantitative agreement with the experiment. Internal optical losses of 10-15 cm-1 and peak modal gain of 24 cm-1 are measured at threshold and a peak material gain is estimated to be 1500 cm-1 at current density of 2 kA/cm-2, which agrees well with the calculated value of 1560 cm-1. The theoretical calculations also enabled us to identify and quantify Bi composition variations across the wafer and Bi-induced inhomogeneous broadening of the optical spectra.
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- 2017
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16. GaAs1−xBix/GaNyAs1−y type-II quantum wells: novel strain-balanced heterostructures for GaAs-based near- and mid-infrared photonics
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Christopher A. Broderick, Shirong Jin, Igor P. Marko, Konstanze Hild, Peter Ludewig, Zoe L. Bushell, Wolfgang Stolz, Judy M. Rorison, Eoin P. O’Reilly, Kerstin Volz, and Stephen J. Sweeney
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Semiconductor lasers ,Electronic structure ,Condensed Matter::Materials Science ,Electronic properties and materials ,Condensed Matter::Other ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Article - Abstract
The potential to extend the emission wavelength of photonic devices further into the near- and mid-infrared via pseudomorphic growth on conventional GaAs substrates is appealing for a number of communications and sensing apThe potential to extend the emission wavelength of photonic devices further into the near- and mid-infrared via pseudomorphic growth on conventional GaAs substrates is appealing for a number of communications and sensing applications. We present a new class of GaAs-based quantum well (QW) heterostructure that exploits the unusual impact of Bi and N on the GaAs band structure to produce type-II QWs having long emission wavelengths with little or no net strain relative to GaAs, while also providing control over important laser loss processes. We theoretically and experimentally demonstrate the potential of GaAs1−xBix/GaNyAs1−y type-II QWs on GaAs and show that this approach offers optical emission and absorption at wavelengths up to ~3 µm utilising strain-balanced structures, a first for GaAs-based QWs. Experimental measurements on a prototype GaAs0.967Bi0.033/GaN0.062As0.938 structure, grown via metal-organic vapour phase epitaxy, indicate good structural quality and exhibit both photoluminescence and absorption at room temperature. The measured photoluminescence peak wavelength of 1.72 μm is in good agreement with theoretical calculations and is one of the longest emission wavelengths achieved on GaAs to date using a pseudomorphically grown heterostructure. These results demonstrate the significant potential of this new class of III-V heterostructure for long-wavelength applications.
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- 2017
17. Enhancing the efficiency of the intermediate band solar cells by introducing:carrier losses, alloying and strain
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Wanshu Xiong, Judy M Rorison, and Qiao-Yi Wang
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Materials science ,business.industry ,Band gap ,Wide-bandgap semiconductor ,02 engineering and technology ,Atomic and Molecular Physics, and Optics ,Semimetal ,Multiple exciton generation ,Condensed Matter::Materials Science ,020210 optoelectronics & photonics ,Band bending ,Semiconductor ,0202 electrical engineering, electronic engineering, information engineering ,Optoelectronics ,Direct and indirect band gaps ,Electrical and Electronic Engineering ,business ,Quasi Fermi level - Abstract
A detailed balance model is used with a blackbody radiation function todetermine the efficiency of an intermediate band solar cell including carrier losses from the intermediate band. The effect of the energy gap of the host semiconductor is examined as a function of the intermediate band position in the energy gap and the host semiconductor energy gap. Generally the optimum intermediate band level is found to decrease within the energy gap to mitigate the carrier losses and it is found that carrier losses are less detrimental to small energy gap materials. We therefore focus the study on the role of carrier losses in wide bandgap semiconductor intermediate band solar cell systems such as the GaN semiconductor with an Mn impurity band. Experimentally the Mn acceptor level in the GaN energy gap is found to be 1.8 eV above the valence band which is 199 meV off the ideal IB neglecting losses which reduces the efficiency to 21.36%. We demonstrate how carrier losses can be introduced into the system to shift the optimum IB position. Introducing carrier losses of 70% from the intermediate band, shifts the optimum intermediate band position to 1.8 eV above the valence band and increases the efficiency to 23.41%. We compare this to the effect of alloying the GaN and introducing biaxial strain to shift the effective position of the Mn impurity band within the bandgap to increase theefficiency.
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- 2017
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18. Modelling of quantum dot intermediate band solar cells: effect of intermediate band linewidth broadening
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Qiao-Yi Wang and Judy M Rorison
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Materials science ,Photon ,Quantum dot ,Band gap ,Excited state ,Electrical and Electronic Engineering ,Photon energy ,Atomic physics ,Ground state ,Homogeneous broadening ,Atomic and Molecular Physics, and Optics ,Doppler broadening - Abstract
A detailed balanced approach is used to model a quantum-dot intermediate band solar cell (QD-IBSC). A model assuming identical QDs with no carrier losses has peak efficiency of 63.24% for a bandgap of 1.95 eV with the intermediate band (IB) positioned either 1.24 eV above the valence band or below the conduction band. The effect of inhomogeneities in the QDs is introduced by incorporating an inhomogeneous broadening of the IB, and the homogeneous broadening describing life-time broadening effects is also introduced. A Gaussian inhomogeneous broadening of the ground state is considered initially and then other inhomogeneous broadenings are considered, including a ground plus excited state distribution. The inhomogeneous broadening removes state density from the ideal IB energy position and thereby reduces efficiency. However, the homogeneous broadening of the QD-IB levels allows more off-resonance QD states to be able to contribute to absorption of the optimum IB photon. This broadening also allows photons near the optimum IB photon energy to be absorbed as well. Both these effects lead to an increase in efficiency. The inter-play between these inhomogeneous and homogeneous broadening allows the efficiency in realistic inhomogeneous arrays of QDs to remain close to the ideal values.
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- 2014
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19. Theoretical Study on Dilute Nitride 1.3 $\mu{\rm m}$ Quantum Well Semiconductor Optical Amplifiers: Incorporation of N Compositional Fluctuations
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Xiao Sun, Nikolaos Vogiatzis, and Judy M Rorison
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Optical amplifier ,Materials science ,business.industry ,Amplifier ,Optical communication ,Physics::Optics ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Gallium arsenide ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Quantum dot ,Wavelength-division multiplexing ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Quantum well - Abstract
Analysis of the broadband gain of a GaInNAs single quantum well (QW) semiconductor optical amplifier (SOA) is developed considering the tuneability of the gain in detail. The SOA is analyzed as a single device multiwavelength channel amplifier in a wavelength-division-multiplexing (WDM) network. The gain model includes the QW material gain derived using a band anti-crossing model and includes quantum dot (QD) fluctuations in the conduction band arising from compositional fluctuations of N within the QW. The material gain is broadened by adding the gain of the QD-like fluctuations and the QW confined level. Simultaneous amplification of two optical signals is analyzed, one at the peak of the QW gain and one at the peak of the QD distribution gain, and the linear and nonlinear regions are established. In addition, multi-channel signal amplification, appropriate for WDM applications, has been modeled across the frequency range of the QW and the QD-like fluctuations and no wavelength degradation between the channels was observed demonstrating the potential of dilute nitride QW as multiwavelength SOAs at optical communications wavelengths.
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- 2013
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20. Modeling Dilute Nitride 1.3 μm Quantum Well Lasers: Incorporation of N Compositional Fluctuations
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Judy M Rorison, Xiao Sun, and Nikolaos Vogiatzis
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Physics ,Electron density ,Photon ,Condensed matter physics ,Band gap ,Physics::Optics ,Rate equation ,Molecular physics ,Atomic and Molecular Physics, and Optics ,Quantum dot ,Quantum dot laser ,Electrical and Electronic Engineering ,Lasing threshold ,Quantum well - Abstract
Compositional fluctuations of N in Ga0.68In0.32NxAs1-x result in quantum dot (QD)-like fluctuations in the conduction band edge (CBE). The influence of these compositional fluctuations on the performance of Ga 0.68In0.32 NxAs1-x /GaAs quantum well (QW) lasers has been studied using a rate equation approach. Adding N into InGaAs has been observed to reduce the photon luminescence (PL) intensity, broaden the line width, and increase the laser threshold. For low N composition (N ≈ 1%), due to the small density of QD-like fluctuations, the electron density within the fluctuations is below the lasing threshold and they act as defect-related nonradiative centers. However, as N increases (N ≥ 2%), the density of the QD-like fluctuations increases allowing lasing to occur from the QD-like fluctuations. The dynamics of the electrons and photons in both the 2-D QW and the QD-like fluctuations are evaluated. In addition, by adding the gain of the QD-like fluctuations and the QW confined level gain, a broad-band material gain results can be exploited in tuneable lasers.
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- 2013
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21. Modelling escape and capture processes in GaInNAs quantum well solar cells
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Q. Wang, Nikolaos Vogiatzis, O. Kengradomying, Judy M Rorison, and S. Jiang
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Physics ,Effective mass (solid-state physics) ,Condensed matter physics ,Alloy ,engineering ,Electron ,Rate equation ,engineering.material ,Condensed Matter Physics ,Conduction band ,Quantum well - Abstract
Carrier escape and capture processes in a GaInA/GaAs quantum well (QW) and a GaInNAs/GaAs QW are compared through modelling using a rate equation approach. QW compositions corresponding to bandgaps of 0.983 eV, 1.000 eV and 1.100 eV are considered for applications in solar cells. For GaInAs a standard alloy model is used, including strain effects, while for GaInNAs the Band Anticrossing (BAC) model is used. The roles of 1. the conduction band QW barrier height and 2. the corresponding effective mass in affecting the electron escape and capture in the QW are considered in detail. The contribution of photogenerated currents from the barrier and QW are considered. The effect of QW depth is found to be larger than changes in the electron effective mass. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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- 2013
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22. Tailoring broadband gain incorporating quantum dot fluctuations for a GaInNAs semiconductor optical amplifier
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Judy M Rorison, Xiao Sun, and Nikolaos Vogiatzis
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Optical amplifier ,education.field_of_study ,Photoluminescence ,Materials science ,business.industry ,Population ,Electron dynamics ,Electron ,Condensed Matter Physics ,Quantum dot ,Broadband ,Optoelectronics ,business ,education ,Quantum - Abstract
It has been observed experimentally that the band edge photoluminescence (PL) of GaxIn1-xNyAs1-yquantum well (QW) materials is broadened due to compositional fluctuations with N distribution. These fluctuations can be modelled as quantum dot-like region at the conduction band minimum in as-grown GaInNAs/GaAs QWs. We have developed a rate-equation approach to describe the distribution of electrons in the QW and QD-like fluctuations which include the carrier recombination from both the conventional 2D QW layer and the inhomogeneous dot-like fluctuations. The electron dynamics in the QW and QDs states are examined and the resulting carrier population and broadband gain is derived for a single QW. This is then applied to the design of a broadband gain multi-QW semiconductor optical amplifier (SOA). (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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- 2013
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23. Dilute bismide alloys grown on GaAs and InP substrates for improved near- and mid-infrared semiconductor lasers
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Stephen J. Sweeney, Wanshu Xiong, Christopher A. Broderick, Judy M Rorison, and Eoin P. O'Reilly
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010302 applied physics ,Materials science ,business.industry ,long-wavelength semiconductor lasers ,02 engineering and technology ,dilute bismide alloys ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Semiconductor laser theory ,law.invention ,Highly-mismatched semiconductors ,law ,0103 physical sciences ,Optoelectronics ,Semiconductor optical gain ,Spontaneous emission ,0210 nano-technology ,Electronic band structure ,business ,Tunable laser ,Quantum well ,Diode - Abstract
We present an analysis of dilute bismide quantum well (QW) lasers grown on GaAs and InP substrates. Our theoretical analysis is based upon a 12-band k·p Hamiltonian which directly incorporates the strong impact of Bi incorporation on the band structure using a band-anticrossing approach. For GaBiAs QWs grown on GaAs we analyse the device performance as a function of Bi composition, and quantify the potential to use GaBiAs alloys to realise highly efficient, temperature stable 1.55 µm lasers. We compare our calculations to measured spontaneous emission (SE) and gain spectra for first-generation GaBiAs lasers and demonstrate quantitative agreement between theory and experiment. We also present a theoretical analysis of InGaBiAs alloys grown on InP substrates. We show that this material system is well suited to the development of mid-infrared lasers, and offers the potential to realise highly efficient InP-based diode lasers incorporating type-I QWs and emitting at > 3 µm. We quantify the theoretical performance of this new class of mid-infrared lasers, and identify optimised structures for emission across the application-rich 3 – 5 µm wavelength range. Our results highlight and quantify the potential of dilute bismide alloys to overcome several limitations associated with existing GaAs- and InP-based near- and mid-infrared laser technologies.
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- 2016
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24. GaAs-based dilute bismide semiconductor lasers: Theory vs. experiment
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Judy M Rorison, Christopher A. Broderick, Eoin P. O'Reilly, Igor P. Marko, and Stephen J. Sweeney
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010302 applied physics ,Materials science ,Condensed matter physics ,business.industry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Semiconductor laser theory ,law.invention ,Condensed Matter::Materials Science ,symbols.namesake ,law ,0103 physical sciences ,symbols ,Optoelectronics ,Semiconductor alloys ,Semiconductor optical gain ,Spontaneous emission ,0210 nano-technology ,business ,Electronic band structure ,Hamiltonian (quantum mechanics) ,Quantum well - Abstract
We present a theoretical analysis of the electronic and optical properties of near-infrared dilute bismide quantum well (QW) lasers grown on GaAs substrates. Our theoretical model is based upon a 12-band kp Hamiltonian which explicitly incorporates the strong Bi-induced modifications of the band structure in pseudomorphically strained GaBixAs1x alloys. We outline the impact of Bi on the gain characteristics of ideal GaBixAs1x/(Al)GaAs devices, compare the results of our theoretical calculations to experimental measurements of the spontaneous emission (SE) and optical gain – a first for this emerging material system – and demonstrate quantitative agreement between theory and experiment. Through our theoretical analysis we further demonstrate that this novel class of III-V semiconductor alloys has strong potential for the development of highly efficient GaAs-based semiconductor lasers which promise to deliver uncooled operation at 1.55 m.
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- 2016
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25. Optical gain in GaAsBi/GaAs quantum well diode lasers
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Wolfgang Stolz, Kerstin Volz, Shirong Jin, Judy M Rorison, P. Ludewig, Eoin P. O'Reilly, Igor P. Marko, Stephen J. Sweeney, and Christopher A. Broderick
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010302 applied physics ,Semiconductor lasers ,Amplified spontaneous emission ,Multidisciplinary ,Materials science ,Laser diode ,business.industry ,Photonic devices ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,7. Clean energy ,Article ,law.invention ,Semiconductor laser theory ,law ,0103 physical sciences ,Optoelectronics ,Semiconductor optical gain ,Spontaneous emission ,0210 nano-technology ,business ,Quantum well ,Diode - Abstract
Electrically pumped GaAsBi/GaAs quantum well lasers are a promising new class of near-infrared devices where, by use of the unusual band structure properties of GaAsBi alloys, it is possible to suppress the dominant energy-consuming Auger recombination and inter-valence band absorption loss mechanisms, which greatly impact upon the device performance. Suppression of these loss mechanisms promises to lead to highly efficient, uncooled operation of telecommunications lasers, making GaAsBi system a strong candidate for the development of next-generation semiconductor lasers. In this report we present the first experimentally measured optical gain, absorption and spontaneous emission spectra for GaAsBi-based quantum well laser structures. We determine internal optical losses of 10–15 cm−1 and a peak modal gain of 24 cm−1, corresponding to a material gain of approximately 1500 cm−1 at a current density of 2 kA cm−2. To complement the experimental studies, a theoretical analysis of the spontaneous emission and optical gain spectra is presented, using a model based upon a 12-band k.p Hamiltonian for GaAsBi alloys. The results of our theoretical calculations are in excellent quantitative agreement with the experimental data and together provide a powerful predictive capability for use in the design and optimisation of high efficiency lasers in the infrared.
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- 2016
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26. Theory of InGaBiAs dilute bismide alloys for highly efficient InP-based mid-infrared semiconductor lasers
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Wanshu Xiong, Christopher A. Broderick, and Judy M Rorison
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010302 applied physics ,Materials science ,business.industry ,Mid infrared ,Material system ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Epitaxy ,Laser ,01 natural sciences ,Semiconductor laser theory ,law.invention ,law ,0103 physical sciences ,Optoelectronics ,0210 nano-technology ,Electronic band structure ,business ,Quantum well ,Diode - Abstract
We present a theoretical analysis of the properties and performance of mid-infrared dilute bismide quantum well (QW) lasers grown on InP substrates. We analyse the band structure of strained InGaBiAs alloys and quantify their potential for the development of mid-infrared semiconductor lasers. In addition to identifying the permissible growth combinations for this class of laser structures, we perform a comprehensive analysis of the performance of a series of ideal laser structures. We investigate the variation of key material and device parameters on the alloy composition, QW thickness and epitaxial strain, and on this basis identify optimised laser structures for emission across the 3 – 5 m wavelength range. Our theoretical analysis suggests that InP-based dilute bismide alloys are an extremely promising candidate material system for the development of highly efficient and temperature stable laser diodes operating in the mid-infrared, and also that this class of laser structures is highly compatible with existing InP-based device architectures.
- Published
- 2016
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27. Diode pumped 850 nm vertical-cavity surface-emitting laser
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Judy M Rorison and M. Othman
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Materials science ,business.industry ,Doping ,Single-mode optical fiber ,Physics::Optics ,Nitride ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Vertical-cavity surface-emitting laser ,law.invention ,Optical pumping ,Optics ,law ,Optoelectronics ,Continuous wave ,Electrical and Electronic Engineering ,business ,Diode - Abstract
Very little, if any, has been published on optically pumped 850 nm vertical-cavity surface-emitting lasers (VCSELs), particularly for doped structures. This paper investigates GaAs-based VCSELs which have not been optimized for optical pumping work. Characterisation was carried out for both pulsed and continuous wave (CW). Pulsed operation causes a lower rise in temperature, thus postponing the onset of thermal rollover, and allowing the device to be operated at higher powers. A threshold of ∼160 kW/cm 2 , and single mode output with incident power density of up to 225 kW/cm 2 were obtained. From the simulation work done, it has been observed that for optically pumped VCSELs, at higher pump density, there was faster turn on and higher output power, and that dilute nitride active material give better output performance compared to GaAs.
- Published
- 2011
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28. Comparative Study of Mode Control in Vertical-Cavity Surface-Emitting Lasers With Photonic Crystal and Micropillar Etching
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Martin J Cryan, P.S. Ivanov, Judy M Rorison, and Peter J Heard
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Materials science ,Equivalent series resistance ,business.industry ,Slope efficiency ,Condensed Matter Physics ,Laser ,Distributed Bragg reflector ,Atomic and Molecular Physics, and Optics ,law.invention ,Semiconductor laser theory ,Optics ,Distributed Bragg reflector laser ,law ,Etching (microfabrication) ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Photonic crystal - Abstract
The dependence of spectral, power versus current and small-signal modulation characteristics versus the etch depth in two types of surface-etched vertical-cavity surface-emitting lasers (VCSELs) are experimentally and theoretically investigated. One type has a photonic crystal (PC) fabricated in the top distributed Bragg reflector (DBR), whereas the second type has a micropillar (MP) created by removing the DBR surrounding it. The aim of both fabrication designs is to improve the single-mode high-power output. Theoretical and experimental results are found to be in qualitative agreement. It is shown that mode-selective optical losses, introduced by the etched holes of the PC in the DBR, control the optical modes of the PC-VCSEL. Single-fundamental-mode radiation is observed for deeply etched PC- and MP-VCSELs. In contrast, improved modulation characteristics are found for shallowly etched devices. Higher-order single-mode generation with improved modulation characteristics is demonstrated for PC-VCSELs with an etch depth of 1.54 μm. PC-VCSELs demonstrate higher slope efficiency, lower threshold current, and series resistance compared with MP-VCSELs of the same etching depth.
- Published
- 2011
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29. Electron transport in bulk GaAsN
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Judy M Rorison and Nikolaos Vogiatzis
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chemistry.chemical_compound ,Electron mobility ,Steady state ,chemistry ,Field (physics) ,Scattering ,Phonon ,Resonance ,Polar ,Gallium nitride ,Atomic physics ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials - Abstract
We present theoretical results on the steady state characteristics of bulk GaAs 1―x N x using the single electron Monte-Carlo method (x ≤ 0.4%). Two equivalent models are used. The first includes a GaAs band with a strong localized nitrogen resonance. The second model uses the band anti-crossing model, in which the localized N level interacts with the GaAs band strongly perturbing the conduction band. We obtain two negative differential velocity peaks from the first model which we associate with N scattering and polar optical phonon emission (POPem). From the second model only one peak is obtained associated with POPem. The first model gives very good agreement with experimental low field mobility. We use this model to include additional scattering resonances related with the pair and larger cluster nitrogen states. Further reduction of the mobility and convergence towards the experimental values is observed.
- Published
- 2011
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30. Modeling spin relaxation in semiconductor quantum wells: modifying the Elliot process
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Martin P Vaughan and Judy M Rorison
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0301 basic medicine ,Physics ,Condensed matter physics ,Spin states ,Condensed Matter::Other ,Scattering ,Point reflection ,Spin–orbit interaction ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,spin relaxation ,Electronic, Optical and Magnetic Materials ,03 medical and health sciences ,Superposition principle ,quantum wells ,030104 developmental biology ,Amplitude ,Materials Chemistry ,Condensed Matter::Strongly Correlated Electrons ,Wave vector ,spin-orbit interaction ,Electrical and Electronic Engineering ,Quantum well - Abstract
A model of the Elliot process for spin relaxation is developed that explicitly incorporates the Dresselhaus spin-splitting of the conduction band in semiconductors lacking an inversion symmetry. It is found that this model reduces to existing models in bulk if the scattering matrices are constructed from a superposition of eigenstates. It is shown that the amplitude for intra-sub-band spin relaxation disappears in quantum wells on the basis of existing models. However, an amplitude due to the Dresselhaus spin-splitting remains, becoming increasingly important as the well becomes narrower. It is also shown that this component does not disappear for scattering between spin states at the same wavevector. It is concluded that for quantum wells and lower dimensional semiconductors that this modified model should be used in analysis of the spin dynamics.
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- 2018
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31. Theoretical investigation of static and dynamic characteristics of vertical-cavity surface-emitting lasers with incorporated two-dimensional photonic crystals
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Pavel S. Ivanov and Judy M Rorison
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Materials science ,Multi-mode optical fiber ,business.industry ,Single-mode optical fiber ,Laser ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Vertical-cavity surface-emitting laser ,law.invention ,Semiconductor laser theory ,Optics ,Lattice constant ,Modulation ,law ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Photonic crystal - Abstract
A dynamical model of oxide-confined Vertical-Cavity Surface-Emitting Lasers (VCSELs) with two-dimensional photonic crystals (PCs) incorporated within them so called PC-VCSELs is presented and used to optimise designs for high-power single-mode operation. Three PC-VCSEL designs are considered: (I) with holes in the top DBRs, (II) with PC holes situated between their DBRs and (III) with PC holes etched through the entire VCSEL. A simulated design for a PC-VCSEL of type (I) with holes of d = 2 μm diameter, a = 4 μm lattice constant (d/a = 0.5) and 2.2 μm depth was found to improve the single mode behaviour but not enough to establish single mode behaviour for large apertures. The modulation behaviour was not degraded by the PC. Simulations of type (II) and (III) PC-VCSELs, with the same parameters, have shown multimode operation and degraded modulation properties. Simulations of PC-VCSELs of type (III) with holes of d = 0.2 μm diameter and a = 0.4 μm lattice constant (d/a = 0.5) have shown improved modulation properties and enhanced single mode power for small apertures. In simulation, PC-VCSELs incorporating multiple PC-defects have shown order of magnitude increases in the single mode output power. However, the modulation properties of these VCSELs show degradation due to gain saturation and hopping of the optical modes localized within the PC defects.
- Published
- 2010
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32. Investigations of repetition rate stability of a mode-locked quantum dot semiconductor laser in an auxiliary optical fiber cavity
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Erwin Bente, W. Elsaer, Judy M Rorison, John G. McInerney, Jose Pozo, Kresten Yvind, Stefan Breuer, Asier Villafranca, Nikolaos Vogiatzis, Mirvais Yousefi, TNO Industrie en Techniek, Photonic Integration, and Chemical Engineering and Chemistry
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Pulse repetition frequency ,Optical fiber ,Materials science ,NI - Nano Instrumentation ,Laser stability ,Semiconductor laser theory ,law.invention ,Optics ,Physics & Electronics ,law ,Pulse wave ,Electrical and Electronic Engineering ,Jitter ,Semiconductor lasers ,Laser resonators ,TS - Technical Sciences ,Industrial Innovation ,business.industry ,Condensed Matter Physics ,Laser ,Atomic and Molecular Physics, and Optics ,Quantum dot laser ,Laser absorbers ,Radio frequency ,Electronics ,business - Abstract
We have investigated experimentally the pulse train (mode beating) stability of a monolithic mode-locked multi-section quantum-dot laser with an added passive auxiliary optical fiber cavity. Addition of the weakly coupled (∼ - 24 dB) cavity reduces the current-induced shift dv / dl of the principal peak in the RF spectrum (the effective pulse repetition frequency) by more than an order of magnitude, from -39.5 to - 2.3 kHz/mA. The rms timing jitter of the pulse train is simultaneously reduced from 1.4 to 0.9 ps. © 2009 IEEE.
- Published
- 2010
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33. Single impurity Anderson model and band anti-crossing in the Ga1-xInxNyAs1-ymaterial system
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Judy M Rorison and Nikolaos Vogiatzis
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Condensed matter physics ,Chemistry ,Band gap ,Anderson's rule ,Surfaces and Interfaces ,Condensed Matter Physics ,Semimetal ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Bound state ,Materials Chemistry ,Condensed Matter::Strongly Correlated Electrons ,Direct and indirect band gaps ,Electrical and Electronic Engineering ,Electronic band structure ,Anderson impurity model ,Quasi Fermi level - Abstract
The role of the single-N impurity in the GaInNAs system is evaluated using the single impurity Anderson model. The N impurities can act either as scattering resonances or as bound states depending on their energy position. For the former case, using self-energy calculations and Matsulbara Green's functions we investigate the nature of the mixed single-N state (energy broadening, shift). The effect of this interaction on the perturbed conduction subbands is also examined. The single impurity Anderson model results in a complex band structure. The real part of the band structure can be directly related to the dispersion obtained with the band anti-crossing model and is in very good agreement The imaginary bandstructure contains further information about the mixing of the nitrogen state and the conduction band which is not contained within the band anti-crossing model.
- Published
- 2008
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34. Optical Properties of Barium Strontium Titanate (BST) Ferroelectric Thin Films
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Yiannis Koutsonas, Judy M Rorison, S. Yu, M. Hill, Timothy J. Jackson, Martin J Cryan, A. K. Bain, Michael J. Lancaster, and R. Varrazza
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Diffraction ,Materials science ,business.industry ,Condensed Matter Physics ,Ferroelectricity ,Electronic, Optical and Magnetic Materials ,Pulsed laser deposition ,Wavelength ,Optics ,Dispersion relation ,Optoelectronics ,Thin film ,business ,Refractive index ,Single crystal - Abstract
Barium strontium titanate (Ba0.05Sr0.95TiO3) ferroelectric thin films have been prepared on single crystal [001] MgO substrates using the pulsed laser deposition method. The X-ray diffraction (XRD) analysis show the films were oriented with the [001] direction perpendicular to the plane of the substrate. The refractive index of Ba0.05Sr0.95TiO3 is determined from model fitting with the calculated data of the reflectivity of Ba0.05Sr0.95TiO3 in the wavelength 1450–1580 nm at the room temperature. The dispersion curve decreases gradually with increasing wavelength. The average value of the refractive index is found to be 1.985 in the wavelength 1450–1580 nm which is important for optoelectronic device applications.
- Published
- 2007
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35. N‐N pair effects on GaInNAs semiconductor optical amplifiers
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D Alexandropoulos, Nikolaos Vogiatzis, Yn Qiu, Dimitris Syvridis, Judy M Rorison, and J. Pozo
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Optical amplifier ,Amplified spontaneous emission ,Valence (chemistry) ,Semiconductor ,business.industry ,Chemistry ,Amplifier ,Optoelectronics ,Rate equation ,Condensed Matter Physics ,business ,Conduction band - Abstract
We explore the effects of N-N pairs on the amplifying properties of GaInNAs based Semiconductor Optical Amplifiers. The bandstructure of GaInNAs is calculated with the 3 band anti-crossing model to account for the N-N pairs for the conduction band and k·p theory for the valence bands. For the calculation of the GaInNAs amplifier properties we adopt a multi-sectioning approach to the rate equation that accounts for amplified spontaneous emission. Based on these we discuss the merits of N-N pairs for GaInNAs semiconductor optical amplifiers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
- Published
- 2007
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36. Exponential operator for the Schrödinger equation in stretched coordinates
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GB Ren and Judy M Rorison
- Subjects
Physics ,Truncation error ,Momentum operator ,Mathematical analysis ,Structure (category theory) ,Finite difference method ,General Physics and Astronomy ,Schrödinger equation ,Momentum ,symbols.namesake ,Reciprocal lattice ,Quantum mechanics ,symbols ,Ideal (ring theory) - Abstract
We present a new scheme for solving the time-dependent Schrodinger equation in analytically stretched coordinates. The algorithm is based on splitting the time evolution operator e − i e ( T + V ) and evaluating the momentum operation ( e − i e T ) in a designed reciprocal space. Compared with the conventional finite difference method, the proposed algorithm is stable and the accuracy is greatly improved with a truncation error is proportional to o ( Δ N + 2 ) , where Δ is the grid spacing and N stands for the grid points in each directions. The total computing effort is roughly same with the finite difference scheme. It is ideal to investigate localized states with confining potential. We have derived the explicit expressions of the momentum operator in the second-order and the 4th-order time evolution operator. To test the proposed algorithm, we employ it in the electronic calculation of 3-dimensional GaN/Al0.2Ga0.8N quantum dot structure.
- Published
- 2005
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37. Focused ion beam-based fabrication of nanostructured photonic devices
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L. Tian, D.C. Sanz, Pavel S. Ivanov, M. Hill, Peter J Heard, Judy M Rorison, Martin J Cryan, and Siyuan Yu
- Subjects
Materials science ,business.industry ,photonic crystals (PhCs) ,Physics::Optics ,Grating ,Focused ion beam ,Atomic and Molecular Physics, and Optics ,Computer Science::Other ,Semiconductor laser theory ,gratings ,Optics ,focused ion beam (FIB) ,Etching (microfabrication) ,Electrical and Electronic Engineering ,Reactive-ion etching ,Photonics ,business ,Diffraction grating ,Photonic crystal - Abstract
This paper presents results for focused ion beam (FIB) processing of two photonic devices: 1) a GaN laser with a fourth-order grating for vertical emission, and 2) a two-dimensional (2-D) photonic crystal (PhC) structure. For the GaN laser, both L-I and I-V results are shown before and after etching, and vertical emitted power as a function of the distance along grating is shown. A finite element (FE)-based electromagnetic model is developed to support the measured results and is used to predict the optimum grating depth. For the 2-D photonic crystal, direct FIB etching is used to create a PhC in a standard InP waveguide structure. Measured and modeled transmission results are compared, and there is good agreement for band edge position. A detailed study of hole shape is presented, and this leads to the development of a multistage etching procedure involving both reactive ion etching and inductively coupled plasma etching. This results in a much improved hole shape.
- Published
- 2005
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38. Characterization of the temperature sensitivity of gain and recombination mechanisms in 1.3-/spl mu/m AlGaInAs MQW lasers
- Author
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J.C.L. Yong, J.K. White, T.J. Houle, B. Garrett, A.J. SpringThorpe, Judy M Rorison, C Marinelli, Ian H. White, and Siyuan Yu
- Subjects
Materials science ,Differential gain ,Auger effect ,business.industry ,Gain ,Analytical chemistry ,Carrier lifetime ,Atmospheric temperature range ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Semiconductor laser theory ,symbols.namesake ,symbols ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Current density ,Diode - Abstract
The potential of 1.3-/spl mu/m AlGaInAs multiple quantum-well (MQW) laser diodes for uncooled operation in high-speed optical communication systems is experimentally evaluated by characterizing the temperature dependence of key parameters such as the threshold current, transparency current density, optical gain and carrier lifetime. Detailed measurements performed in the 20/spl deg/C-100/spl deg/C temperature range indicate a localized T/sub 0/ value of 68 K at 98/spl deg/C for a device with a 2.8 /spl mu/m ridge width and 700-/spl mu/m cavity length. The transparency current density is measured for temperatures from 20/spl deg/C to 60/spl deg/C and found to increase at a rate of 7.7 A/spl middot/cm/sup -2//spl middot/ /spl deg/C/sup -1/. Optical gain characterizations show that the peak modal gain at threshold is independent of temperature, whereas the differential gain decreases linearly with temperature at a rate of 3/spl times/10/sup -4/ A/sup -1//spl middot//spl deg/C/sup -1/. The differential carrier lifetime is determined from electrical impedance measurements and found to decrease with temperature. From the measured carrier lifetime we derive the monomolecular ( A), radiative (B), and nonradiative Auger (C) recombination coefficients and determine their temperature dependence in the 20/spl deg/C-80/spl deg/C range. Our study shows that A is temperature independent, B decreases with temperature, and C exhibits a less pronounced increase with temperature. The experimental observations are discussed and compared with theoretical predictions and measurements performed on other material systems.
- Published
- 2005
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39. Deconvolution of optical broadening in semiconductors
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Judy M Rorison, G. B. Ren, and P Blood
- Subjects
Physics ,General Physics and Astronomy ,Spectral line ,Gaussian broadening ,symbols.namesake ,Fourier transform ,Quantum mechanics ,symbols ,Spontaneous emission ,Stimulated emission ,Deconvolution ,Atomic physics ,Homogeneous broadening ,Doppler broadening - Abstract
Gain spectra in semiconductors have often been measured by using Henry's formula in which directly measurable spontaneous emission spectra are transformed to gain spectra, but optical broadening is neglected. We have studied the effect of the optical broadening to the Henry's formula and have derived a more general relation by deconvolution of the optical broadening using Fourier transformation. Lorentz, Gauss and sech-lineshape optical broadening have been examined in detail. Numerical examples for a 50 A GaN/Al 0.2 Ga 0.8 N quantum well have been used to transform the spontaneous emission to the gain spectrum using the general relation for the case of the sech-lineshape broadening. We have also derived a rather simple formula similar to the Henry's formula for the Gaussian broadening mechanism.
- Published
- 2004
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40. Design of multiweight unipolar codes for multimedia optical cdma applications based on pairwise balanced designs
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Ivan B. Djordjevic, Judy M Rorison, and Bane Vasic
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Block code ,Multimedia ,Computer science ,Code division multiple access ,Integer lattice ,Optical communication ,computer.software_genre ,Atomic and Molecular Physics, and Optics ,Bit error rate ,Electronic engineering ,Pairwise comparison ,computer ,Decoding methods ,Coding (social sciences) - Abstract
A novel class of constant-length variable-weight optical orthogonal codes is proposed that can support multimedia services with different data rates and quality-of-service requirements. The construction is based on the pairwise balanced designs, or more specifically, on an incidence structure defined on an integer lattice. Proposed codes are suitable for spectral-amplitude coding, fast-frequency hopping, and time-spreading encoding in multimedia environment. A novel dual-balanced decoder is proposed capable of canceling multiuser interference in multimedia applications for spectral-amplitude-coding schemes employing the unipolar codes having nonfixed in-phase cross correlation.
- Published
- 2003
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41. Eye-opening lattice work
- Author
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A.B. Massara, J.C.L. Yong, Peter J Heard, L.J. Sargent, Mariangela Gioannini, and Judy M Rorison
- Subjects
3D optical data storage ,Work (thermodynamics) ,Eye opening ,Materials science ,business.industry ,Semiconductor materials ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Physics::Optics ,Laser ,Electronic, Optical and Magnetic Materials ,law.invention ,Optics ,law ,Lattice (order) ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Instrumentation ,Refractive index ,Photonic crystal - Abstract
The 2-D lattice laser is a promising low-cost device for high-speed optical data communications applications.
- Published
- 2003
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42. 1.3-μm quantum-well InGaAsP, AlGaInAs, and InGaAsN laser material gain: a theoretical study
- Author
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J.C.L. Yong, Judy M Rorison, and Ian H. White
- Subjects
Materials science ,business.industry ,Material system ,Condensed Matter Physics ,Laser ,Atomic and Molecular Physics, and Optics ,Active layer ,law.invention ,Wavelength ,Optics ,law ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Quantum well - Abstract
Due to the keen interest in improving the high-speed and high-temperature performance of 1.3-/spl mu/m wavelength lasers, we compare, for the first time, the material gain of three different competing active layer materials, namely InGaAsP-InGaAsP, AlGaInAs-AlGaInAs, and InGaAsN-GaAs. We present a theoretical study of the gain of each quantum-well material system and present the factors that influence the material gain performance of each system. We find that AlGaInAs and InGaAsN active layer materials have substantially better material gain performance than the commonly used InGaAsP, both at room temperature and at high temperature.
- Published
- 2002
- Full Text
- View/download PDF
43. Calculation of the temperature dependence of hot electron scattering in heavily p-doped GaAs using a high-temperature approximation to the dielectric function
- Author
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Judy M Rorison, V. Narayan, and J C Inkson
- Subjects
Physics ,Condensed matter physics ,Scattering ,Maxwell–Boltzmann statistics ,Dielectric ,Electron ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Condensed Matter::Superconductivity ,Quasiparticle ,Condensed Matter::Strongly Correlated Electrons ,Landau damping ,Electrical and Electronic Engineering ,Atomic physics ,Random phase approximation ,Plasmon - Abstract
Using a high-temperature approximation to the dielectric function within the random phase approximation, we calculate hot electron scattering rates, as a function of temperature and doping density, in p-doped GaAs. The dielectric function of the holes contains contributions from intraband excitations and interband excitations. The former reduces to an analytic form within the two pole approximation (which used Boltzmann statistics), whereas the latter was calculated numerically. The collective excitation mode of the holes was defined by intraband excitations, since at very small wavevectors, the interband excitations vanish. However, at low temperature the interband excitations were found to be the dominant Landau damping mechanism, which strongly suppressed the plasmon at moderate doping levels. At high temperature the excitations from the heavy to light band were partially suppressed, and the plasmon was not overwhelmingly Landau damped by either interband or intraband excitations. At room temperature, an analytic dielectric function where the interband excitations have been neglected, may be used to accurately calculate hot electron mean free paths. This approximation was found to become more accurate with lower doping levels, but was not appropriate at low temperature.
- Published
- 2002
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44. Investigation of 2-D-lattice distributed reflector lasers
- Author
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Judy M Rorison, J.C.L. Yong, L.J. Sargent, A.B. Massara, Peter J Heard, and Mariangela Gioannini
- Subjects
Materials science ,business.industry ,Optical communication ,Physics::Optics ,Condensed Matter Physics ,Laser ,Distributed Bragg reflector ,Waveguide (optics) ,Atomic and Molecular Physics, and Optics ,Semiconductor laser theory ,law.invention ,Optics ,law ,Optoelectronics ,Hexagonal lattice ,Electrical and Electronic Engineering ,business ,Diffraction grating ,Tunable laser - Abstract
The introduction of a deep-etched hexagonal lattice of round holes around a short section of the ridge waveguide of a Fabry-Perot laser can be used to create single-mode lasers suitable for high-speed data communications. A detailed characterization of the operating characteristics of the two-dimensional-lattice laser is presented. In addition, modeling of gain, reflectivity, and waveguide properties is used to explain experimentally observed results.
- Published
- 2002
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45. Modelling of Intermediate Band Solar Cells: Quantum Dot or Impurity Band — The effect of inhomogeneous broadening
- Author
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Judy M Rorison and Joey Wang
- Subjects
Multiple exciton generation ,Physics ,Intermediate band ,Condensed matter physics ,Impurity ,Band gap ,Quantum dot - Published
- 2014
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46. Theoretical modeling of nonequilibrium optical phonons and electron energy relaxation in GaN
- Author
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Tien-Li Sung, Chin-Yi Tsai, Chin-Yao Tsai, Judy M Rorison, and Chih-Hsiung Chen
- Subjects
Physics ,Electron energy ,Condensed matter physics ,Phonon ,Relaxation (NMR) ,Wide-bandgap semiconductor ,General Physics and Astronomy ,Non-equilibrium thermodynamics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter::Materials Science ,Transverse plane ,Relaxation rate ,Condensed Matter::Superconductivity ,Condensed Matter::Strongly Correlated Electrons ,Longitudinal optical - Abstract
The decay of the zone-center longitudinal optical (LO) phonon in GaN into a transverse optical (TO) phonon and a longitudinal acoustic (LA) phonon is theoretically investigated. Its decay into two LA phonons is forbidden. A theoretical model is presented to study the effect of nonequilibrium LO and TO phonons on the electron energy relaxation rate. The electron energy relaxation time is calculated, and its value is shown to strongly depend on the finite lifetimes of both LO and TO phonons. The individual contributions of A1 mode and E1 mode optical phonons in the overall electron energy relaxation processes are also discussed.
- Published
- 1999
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- View/download PDF
47. Theoretical modeling of the small-signal modulation response of carrier and lattice temperatures with the dynamics of nonequilibrium optical phonons in semiconductor lasers
- Author
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Chin-Yi Tsai, Chin-Yao Tsai, Judy M Rorison, Tien-Li Sung, and Chih-Hsiung Chen
- Subjects
Physics ,Photon ,Condensed matter physics ,Phonon ,Non-equilibrium thermodynamics ,Rate equation ,Electron ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Atomic and Molecular Physics, and Optics ,Semiconductor laser theory ,Condensed Matter::Materials Science ,Lattice (order) ,Electron temperature ,Electrical and Electronic Engineering - Abstract
A theoretical model is presented that is capable of simultaneously simulating the small-signal modulation response of the carrier density, photon density, electron temperature, hole temperature, populations of nonequilibrium longitudinal (LO) and transverse optical (TO) phonons at different wave vectors, and lattice temperature in semiconductor lasers. The phonon dynamics of nonequilibrium LO and TO phonons is calculated from first principles by considering the polar and deformation-potential interactions between carriers and optical phonons. Rate equations of the energy transfer among electrons, holes, photons, optical phonons, and acoustic phonons are given. The small-signal modulation responses of carrier and lattice temperatures are calculated. The different roles of carrier and lattice heating in semiconductor lasers are discussed.
- Published
- 1999
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48. Preface: phys. stat. sol. (c) 5/2
- Author
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Naci Balkan, Mika J. Saarinen, Ceyhun Bulutay, and Judy M Rorison
- Subjects
Physics ,Solid-state physics ,Current (fluid) ,Condensed Matter Physics ,Engineering physics - Published
- 2008
- Full Text
- View/download PDF
49. The Constraints on Quantum-Dot Semiconductor Optical Amplifiers for Multichannel Amplification
- Author
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H.C. Wong, Judy M Rorison, and G.B. Ren
- Subjects
Optical amplifier ,Physics ,Condensed Matter::Other ,business.industry ,Amplifier ,Physics::Optics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Gallium arsenide ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Optics ,Semiconductor ,chemistry ,Quantum dot ,Quantum dot laser ,Wavelength-division multiplexing ,Broadband ,Optoelectronics ,Electrical and Electronic Engineering ,business - Abstract
We report our theoretical studies on the application of InGaAs-GaAs quantum-dot (QD) semiconductor optical amplifier as a single-device multichannel amplifier in the coarse wavelength-division-multiplexing network. Our numerical model exploits the broadened excited states in the QDs to enhance the broadband property of the inhomogeneous QD material
- Published
- 2006
- Full Text
- View/download PDF
50. A detailed theory of excitons in quantum dots
- Author
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Judy M Rorison, M. Boero, G Duggan, and J C Inkson
- Subjects
Physics ,Condensed matter physics ,business.industry ,Exciton ,Quantum-confined Stark effect ,Binding energy ,Surfaces and Interfaces ,Electron ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Semiconductor ,Quantum dot ,Materials Chemistry ,Coulomb ,business ,Quantum - Abstract
Quantum-dot systems are confined semiconductor structures which exhibit a fully discrete spectrum due to the size confinement in all directions. The position of the energy levels inside such structures can be changed by adjusting their geometrical dimensions. Such structures are particularly interesting for optical applications for two reasons: (i) both the electrons and holes are confined in the same small physical region, and therefore the strength of recombination processes is increased, and (ii) by changing the position of the energy levels, one can in principle tune quantum-dot lasers over a wide range of wavelengths. The presence of size confinement gives rise to two competing effects: on one hand it causes an upward shift of the energy levels, and on the other it enhances the Coulomb attraction between electrons and holes. These effects tend to shift the position of the exciton energies in opposite directions, so that a careful modelling of such structures is required in order to understand which is the dominant effect and how the excitons behave as a function of confinement. While there have been several studies on ideal systems, we attempt to model a system more closely aligned to experiment. In this study we investigate: (i) the effect of the shape of the lateral potential of a quantum disk, i.e. parabolic and hard-wall; (ii) the effect of wave-function leakage in the barries; and (iii) the effect of the light-heavy hole mixing on the effective masses.
- Published
- 1997
- Full Text
- View/download PDF
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