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- III-V semiconductors (11)
- Quantum dots (7)
- Self assembly (6)
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- Electron gas (3)
- Etching (3)
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- Molecular beam epitaxy (3)
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- II-V semiconductors (2)
- Photoluminescence (2)
- Promoter activity (2)
- Solar cells (2)
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- Aerodynamics (1)
- Anisotropy (1)
- Atmosphere-land interaction (1)
- Atomic force microscopy (1)
- Automatic weather stations (1)
- B. subtilis (1)
- Biological noise (1)
- Carrier mobility (1)
- Central carbon metabolism (1)
Articles 1 - 30 of 30
Full-Text Articles in Physics
Tensile Gaas(111) Quantum Dashes With Tunable Luminescence Below The Bulk Bandgap, Paul J. Simmonds
Tensile Gaas(111) Quantum Dashes With Tunable Luminescence Below The Bulk Bandgap, Paul J. Simmonds
Paul J. Simmonds
Strain-based band engineering in quantum dots and dashes has been predominantly limited to compressively strained systems. However, tensile strain strongly reduces the bandgaps of nanostructures, enabling nanostructures to emit light at lower energies than they could under compressive strain. We demonstrate the self-assembled growth of dislocation-free GaAs quantum dashes on an InP(111)B substrate, using a 3.8% tensile lattice-mismatch. Due to the high tensile strain, the GaAs quantum dashes luminesce at 110–240 meV below the bandgap of bulk GaAs. The emission energy is readily tuned by adjusting the size of the quantum dashes via deposition thickness. Tensile self-assembly creates new opportunities …
New Quantum Dot Nanomaterials To Boost Solar Energy Harvesting, Paul J. Simmonds
New Quantum Dot Nanomaterials To Boost Solar Energy Harvesting, Paul J. Simmonds
Paul J. Simmonds
Sequential photon absorption processes in semiconductor solar cells represent a route to improving their efficiency.
Effects Of Gaas(Sb) Cladding Layers On Inas/Alassb Quantum Dots, Paul J. Simmonds
Effects Of Gaas(Sb) Cladding Layers On Inas/Alassb Quantum Dots, Paul J. Simmonds
Paul J. Simmonds
The structural and optical properties of InAs self-assembled quantum dots buried in AlAs0.56Sb0.44 barriers can be controlled using GaAs1−xSbx cladding layers. These cladding layers allow us to manage the amount of Sb immediately underneath and above the InAs quantum dots. The optimal cladding scheme has a GaAs layer beneath the InAs, and a GaAs0.95Sb0.05 layer above. This scheme results in improved dot morphology and significantly increased photoluminescence (PL) intensity. Both power-dependent and time-resolved photoluminescence confirm that the quantum dots have type-II band alignment. Enhanced carrier lifetimes in this quantum dot system …
Tensile-Strained Growth On Low-Index Gaas, Paul J. Simmonds, Minjoo Larry Lee
Tensile-Strained Growth On Low-Index Gaas, Paul J. Simmonds, Minjoo Larry Lee
Paul J. Simmonds
We present a comparative study of the growth of tensile-strained GaP on the four low-index surfaces of GaAs: (001), (110), (111)A, and (111)B. For each surface orientation we outline the growth conditions required for smooth GaAshomoepitaxy. We are able to predict the resulting surface morphology when GaP is deposited onto these four GaAssurfaces by considering the influence of surface orientation on tensile strain relief. GaP deposited on GaAs(001) forms extremely smooth, planar layers. In contrast, the elastic relief of tensile strain on both GaAs(110) and GaAs(111)A leads to the three-dimensional self-assembly of GaP into dislocation-free nanostructures. Similarities between tensile and …
Structural And Optical Properties Of Inas/Alassb Quantum Dots With Gaas(Sb) Cladding Layers, Paul J. Simmonds, Ramesh Babu Laghumavarapu, Meng Sun, Andrew Lin, Charles J. Reyner, Baolai Liang, Diana L. Huffaker
Structural And Optical Properties Of Inas/Alassb Quantum Dots With Gaas(Sb) Cladding Layers, Paul J. Simmonds, Ramesh Babu Laghumavarapu, Meng Sun, Andrew Lin, Charles J. Reyner, Baolai Liang, Diana L. Huffaker
Paul J. Simmonds
We investigate the effect of GaAs1−xSbxcladding layer composition on the growth and properties of InAsself-assembledquantum dots surrounded by AlAs0.56Sb0.44 barriers. Lowering Sb-content in the GaAs1−xSbx improves the morphology of the InAs quantum dots and reduces cladding layer alloy fluctuations. The result is a dramatic increase in photoluminescence intensity from the InAs quantum dots, with a peak at 0.87 eV. The emission energy exhibits a cube root dependence on excitation power, consistent with the type-II band alignment of the quantum dots. The characteristics of this quantum dot system show promise for …
Reconciling Molecular Regulatory Mechanisms With Noise Patterns Of Bacterial Metabolic Promoters In Induced And Repressed States, Matthew L. Ferguson, Dominique Le Coq, Matthieu Jules, Stéphane Aymerich, Ovidiu Radulescu, Nathalie Declerck, Catherine A. Royer
Reconciling Molecular Regulatory Mechanisms With Noise Patterns Of Bacterial Metabolic Promoters In Induced And Repressed States, Matthew L. Ferguson, Dominique Le Coq, Matthieu Jules, Stéphane Aymerich, Ovidiu Radulescu, Nathalie Declerck, Catherine A. Royer
Matthew L. Ferguson
Assessing gene expression noise in order to obtain mechanistic insights requires accurate quantification of gene expression on many individual cells over a large dynamic range. We used a unique method based on 2-photon fluorescence fluctuation microscopy to measure directly, at the single cell level and with single-molecule sensitivity, the absolute concentration of fluorescent proteins produced from the two Bacillus subtilis promoters that control the switch between glycolysis and gluconeogenesis. We quantified cell-to-cell variations in GFP concentrations in reporter strains grown on glucose or malate, including very weakly transcribed genes under strong catabolite repression. Results revealed strong transcriptional bursting, particularly for …
Absolute Quantification Of Gene Expression In Individual Bacterial Cells Using Two-Photon Fluctuation Microscopy, Matthew L. Ferguson, Dominique Le Coq, Matthieu Jules, Stéphane Aymerich, Nathalie Declerck, Catherine A. Royer
Absolute Quantification Of Gene Expression In Individual Bacterial Cells Using Two-Photon Fluctuation Microscopy, Matthew L. Ferguson, Dominique Le Coq, Matthieu Jules, Stéphane Aymerich, Nathalie Declerck, Catherine A. Royer
Matthew L. Ferguson
Quantification of promoter activity or protein expression in gene regulatory networks is generally achieved via measurement of fluorescent protein (FP) intensity, which is related to the true FP concentration by an unknown scaling factor, thereby limiting analysis and interpretation. Here, using approaches originally developed for eukaryotic cells, we show that two-photon (2p) fluorescence fluctuation microscopy, specifically scanning number and brightness (sN&B) analysis, can be applied to determine the absolute concentrations of diffusing FPs in live bacterial cells. First, we demonstrate the validity of the approach, despite the small size of the bacteria, using the central pixels and spatial averaging. We …
Meteorological Conditions At Racetrack Playa, Death Valley National Park: Implications For Rock Production And Transport, Ralph D. Lorenz, Brian K. Jackson, Jason W. Barnes, Joseph N. Spitale, Jani Radebaugh, Kevin H. Baines
Meteorological Conditions At Racetrack Playa, Death Valley National Park: Implications For Rock Production And Transport, Ralph D. Lorenz, Brian K. Jackson, Jason W. Barnes, Joseph N. Spitale, Jani Radebaugh, Kevin H. Baines
Brian Jackson
Three decades of weather records at meteorological stations near Death Valley National Park are analyzed in an attempt to gauge the frequency of conditions that might form and erase the famous trails of wind-blown rocks in the mud of Racetrack Playa. Trail formation requires the playa to be wet, followed by strong winds and/or freezing conditions. Weather records are compared with a limited set of meteorological data that were acquired in situ at the playa over three winters and that indicate freezing on 50, 29, and 15 nights during the winters of 2007/08–09/10, respectively, as well as with the hydrological …
Self-Assembly On (111)-Oriented Iii-V Surfaces, Paul J. Simmonds, Minjoo Larry Lee
Self-Assembly On (111)-Oriented Iii-V Surfaces, Paul J. Simmonds, Minjoo Larry Lee
Paul J. Simmonds
We demonstrate the self-assembly of tensile strained GaP into three-dimensional dots on GaAs(111)A. Size and areal density of the dislocation-free GaPdots are readily tunable with both substrate temperature and deposition thickness. GaP dot growth obeys island scaling theory, allowing us to predict dot size distributions a priori.
Molecular Beam Epitaxy Approach To The Graphitization Of Gaas(100) Surfaces, Paul J. Simmonds, John Simon, Jerry M. Woodall, Minjoo Larry Lee
Molecular Beam Epitaxy Approach To The Graphitization Of Gaas(100) Surfaces, Paul J. Simmonds, John Simon, Jerry M. Woodall, Minjoo Larry Lee
Paul J. Simmonds
The authors present a method for obtaining graphitized carbon on GaAs(100) surfaces. Carbon-doped GaAs is grown by molecular beam epitaxy before controlled thermal etching within the growth chamber. An AlAs layer beneath the carbon-doped GaAs acts as a thermal etch stop. As the GaAs is etched away, the carbondopant atoms remain on the surface due to their low vapor pressure. The total number of carbon atoms available is precisely controllable by the doping density and thickness of the carbon-doped GaAs layer. Characteristic phonon modes in Raman spectra from the thermally etchedsurfaces show that the residual surfacecarbon atoms form sp2 …
Molecular Beam Epitaxy Of Metamorphic InYGa1−YP Solar Cells On Mixed Anion GaasXP1−X/Gaas Graded Buffers, Stephanie Tomasulo, John Simon, Paul J. Simmonds, Jonathan Biagiotti, Minjoo L. Lee
Molecular Beam Epitaxy Of Metamorphic InYGa1−YP Solar Cells On Mixed Anion GaasXP1−X/Gaas Graded Buffers, Stephanie Tomasulo, John Simon, Paul J. Simmonds, Jonathan Biagiotti, Minjoo L. Lee
Paul J. Simmonds
The authors have grown metamorphic InyGa1−yP on optimized GaAsxP1−x/GaAs graded buffers via solid source molecular beam epitaxy(MBE) for multijunction solar cell applications. In this work, the authors show that a previously developed kinetic growth model can be used to predict the composition of mixed anion GaAsxP1−x alloys on GaAs as a function of substrate temperature and group-V flux. The advantages of using a high growth temperature of 700 °C are then described, including the minimized dependence of composition on small temperature variations, a linear dependence of film composition on …
Graphitized Carbon On Gaas(100) Substrates, J. Simon, P. J. Simmonds, J. M. Woodall, M. L. Lee
Graphitized Carbon On Gaas(100) Substrates, J. Simon, P. J. Simmonds, J. M. Woodall, M. L. Lee
Paul J. Simmonds
We report on the formation of graphitized carbon on GaAs(100) surfaces by molecular beam epitaxy. We grew highly carbon-doped GaAs on AlAs, which was then thermally etched in situ leaving behind carbon atoms on the surface. After thermal etching, Raman spectra revealed characteristic phonon modes for sp2-bonded carbon, consistent with the formation of graphitic crystallites. We estimate that the graphitic crystallites are 1.5–3 nm in size and demonstrate that crystallite domain size can be increased through the use of higher etch temperatures.
Metamorphic Gaasp Buffers For Growth Of Wide-Bandgap Ingap Solar Cells, J. Simon, S. Tomasulo, P. J. Simmonds, M. Romero, M. L. Lee
Metamorphic Gaasp Buffers For Growth Of Wide-Bandgap Ingap Solar Cells, J. Simon, S. Tomasulo, P. J. Simmonds, M. Romero, M. L. Lee
Paul J. Simmonds
GaAsxP1−x graded buffers were grown via solid source molecular beam epitaxy(MBE) to enable the fabrication of wide-bandgap InyGa1−yP solar cells. Tensile-strained GaAsxP1−x buffers grown on GaAs using unoptimized conditions exhibited asymmetric strain relaxation along with formation of faceted trenches, 100–300 nm deep, running parallel to the [011] direction. We engineered a 6 μm thick grading structure to minimize the faceted trench density and achieve symmetric strain relaxation while maintaining a threading dislocation density of ≤106 cm−2. In comparison, compressively-strained graded GaAsxP1−x buffers on …
Ice Rafts Not Sails: Floating The Rocks At Racetrack Playa, Ralph D. Lorenz, Brian K. Jackson, Jason W. Barnes, Joe Spitale, John M. Keller
Ice Rafts Not Sails: Floating The Rocks At Racetrack Playa, Ralph D. Lorenz, Brian K. Jackson, Jason W. Barnes, Joe Spitale, John M. Keller
Brian Jackson
We suggest that the existence of many of the rock-carved trails at Racetrack Playa in Death Valley National Park is predominantly due to the effect of arbitrarily weak winds on rocks that are floated off the soft bed by small rafts of ice, as also occurs in arctic tidal beaches to form boulder barricades. These ice cakes need not have a particularly large surface area if the ice is adequately thick—the ice cakes allow the rocks to move by buoyantly reducing the reaction and friction forces at the bed, not by increasing the wind drag. The parameter space of ice …
Self-Assembled In0.5Ga0.5As Quantum Dots On Gap, Yuncheng Song, Paul J. Simmonds, Minjoo Larry Lee
Self-Assembled In0.5Ga0.5As Quantum Dots On Gap, Yuncheng Song, Paul J. Simmonds, Minjoo Larry Lee
Paul J. Simmonds
We demonstrate the growth and luminescence of coherently strained In0.5Ga0.5As self-assembled quantum dots on GaP. Cross-sectional and planar-view transmission electron microscopy confirmed the dislocation-free nature of the In0.5Ga0.5As quantum dots and GaP cap layers. Intense photoluminescence from the quantum dots was measured at 80 K and was visible to the unaided eye in ambient lighting. The photoluminescence results show that emission energy can be controlled by varying the In0.5Ga0.5As deposition thickness. In combination with recent advances in the growth of GaP on Si, the In0.5Ga0.5 …
Tensile Strained Island Growth At Step-Edges On Gaas(110), Paul J. Simmonds, M. L. Lee
Tensile Strained Island Growth At Step-Edges On Gaas(110), Paul J. Simmonds, M. L. Lee
Paul J. Simmonds
We report the growth of tensile strained GaP islands on a GaAs(110) surface. Three-dimensional island formation proceeds via a step-edge nucleation process. To explain the dislocation-free nature of these islands, we consider the kinetics of strain relief within the context of a model for dislocation glide as a function of surface orientation and sign of strain.
Physical Basis Of The Inducer-Dependent Cooperativity Of The Central Glycolytic Genes Repressor/Dna Complex, Denis Chaix, Matthew L. Ferguson, Cedric Atmanene, Alain Van Dorsselaer, Sarah Sanglier-Cianférani, Catherine A. Royer, Nathalie Declerck
Physical Basis Of The Inducer-Dependent Cooperativity Of The Central Glycolytic Genes Repressor/Dna Complex, Denis Chaix, Matthew L. Ferguson, Cedric Atmanene, Alain Van Dorsselaer, Sarah Sanglier-Cianférani, Catherine A. Royer, Nathalie Declerck
Matthew L. Ferguson
The Central glycolytic genes Repressor (CggR) from Bacillus subtilis belongs to the SorC family of transcription factors that control major carbohydrate metabolic pathways. Recent studies have shown that CggR binds as a tetramer to its tandem operator DNA sequences and that the inducer metabolite, fructose 1,6-bisphosphate (FBP), reduces the binding cooperativity of the CggR/DNA complex. Here, we have determined the effect of FBP on the size, shape and stoichiometry of CggR complexes with full-length and half-site operator sequence by small-angle X-ray scattering, size-exclusion chromatography, fluorescence cross-correlation spectroscopy and noncovalent mass spectrometry (MS). Our results show that CggR forms a compact …
Tensile Strained Iii-V Self-Assembled Nanostructures On A (110) Surface, Minjoo L. Lee, Paul J. Simmonds
Tensile Strained Iii-V Self-Assembled Nanostructures On A (110) Surface, Minjoo L. Lee, Paul J. Simmonds
Paul J. Simmonds
The vast majority of research on epitaxial quantum dots use compressive strain as the driving force for self-assembly on the (001) surface, with InAs/GaAs(001) and Ge/Si(001) being the best-known examples. In this talk, I will discuss our work on determining the feasibility of growing coherent, tensile-strained III-V nanostructures on a (110) surface. GaP on GaAs(110) was chosen as an initial test system. It is hoped that our efforts on self-assembled, tensile-strained dots on a (110) surface will lead the way to new devices exploiting the fundamental differences between the (110) and (001) surfaces. Furthermore it is anticipated that this work …
Growth Of Metamorphic Ingap For Wide-Bandgap Photovoltaic Junction By Mbe, John Simon, Stephanie Tomasulo, Paul J. Simmonds, Manuel J. Romero, Minjoo Larry Lee
Growth Of Metamorphic Ingap For Wide-Bandgap Photovoltaic Junction By Mbe, John Simon, Stephanie Tomasulo, Paul J. Simmonds, Manuel J. Romero, Minjoo Larry Lee
Paul J. Simmonds
Metamorphic triple-junction solar cells can currently attain efficiencies as high as 41.1%. Using additional junctions could lead to efficiencies above 50%, but require the development of a wide bandgap (2.0-2.2eV) material to act as the top layer. In this work we demonstrate wide bandgap InyGa1-yP grown on GaAsxP1-x via solid source molecular beam epitaxy. Unoptimized tensile GaAsxP1-x buffers grown on GaAs exhibit asymmetric strain relaxation, along with formation of faceted trenches 100-300 nm deep in the [01-1] direction. Smaller grading step size and higher substrate temperatures minimizes the facet trench …
A Comparison Of New Methods For Generating Energy-Minimizing Configurations Of Patchy Particles, Eric Jankowski, Sharon C. Glotzer
A Comparison Of New Methods For Generating Energy-Minimizing Configurations Of Patchy Particles, Eric Jankowski, Sharon C. Glotzer
Eric Jankowski
Increasingly complex particles are pushing the limits of traditional simulation techniques used to study self-assembly. In this work, we test the use of a learning-augmented Monte Carlo method for predicting low energy configurations of patchy particles shaped like “Tetris®” pieces. We extend this method to compare it against Monte Carlo simulations with cluster moves and introduce a new algorithm—bottom-up building block assembly—for quickly generating ordered configurations of particles with a hierarchy of interaction energies.
Molecular Beam Epitaxy Of High Mobility In0.75Ga0.25As For Electron Spin Transport Applications, Paul J. Simmonds, S. N. Holmes, H. E. Beere, I. Farrer, F. Sfigakis, D. A. Ritchie, M. Pepper
Molecular Beam Epitaxy Of High Mobility In0.75Ga0.25As For Electron Spin Transport Applications, Paul J. Simmonds, S. N. Holmes, H. E. Beere, I. Farrer, F. Sfigakis, D. A. Ritchie, M. Pepper
Paul J. Simmonds
The authors describe the molecular beam epitaxy of relaxed, nominally undoped In0.75Ga0.25As–In0.75Al0.25As quantum well structures grown on InP substrates. The maximum two-dimensional electron density is 2 × 1011cm−2, with a peak mobility of 2.2 × 105cm2 V−1s−1 at 1.5K. In high magnetic field, the electron g-factor was shown to have a magnitude of 9.1 ± 0.1 at Landau-level filling factor of 4. The Rashba coefficient, determined from the analysis of the magnetoresistance at high Landau-level filling factor (>12), …
Clathrin Triskelia Show Evidence Of Molecular Flexibility, Matthew L. Ferguson, Kondury Prasad, Hacene Boukari, Dan L. Sackett, Susan Krueger, Eileen M. Lafer, Ralph Nossal
Clathrin Triskelia Show Evidence Of Molecular Flexibility, Matthew L. Ferguson, Kondury Prasad, Hacene Boukari, Dan L. Sackett, Susan Krueger, Eileen M. Lafer, Ralph Nossal
Matthew L. Ferguson
The clathrin triskelion, which is a three-legged pinwheel-shaped heteropolymer, is a major component in the protein coats of certain post-Golgi and endocytic vesicles. At low pH, or at physiological pH in the presence of assembly proteins, triskelia will self-assemble to form a closed clathrin cage, or “basket”. Recent static light scattering and dynamic light scattering studies of triskelia in solution showed that an individual triskelion has an intrinsic pucker similar to, but differing from, that inferred from a high resolution cryoEM structure of a triskelion in a clathrin basket. We extend the earlier solution studies by performing small-angle neutron scattering …
Spin-Orbit Coupling In An In0.52Ga0.48As Quantum Well With Two Populated Subbands, P. J. Simmonds, S. N. Holmes, H. E. Beere, D. A. Ritchie
Spin-Orbit Coupling In An In0.52Ga0.48As Quantum Well With Two Populated Subbands, P. J. Simmonds, S. N. Holmes, H. E. Beere, D. A. Ritchie
Paul J. Simmonds
Structural inversion asymmetry controls the magnitude of Rashba spin-orbit coupling in the electron energy spectrum of a narrow band gap semiconductor. We investigate this effect for a series of two-dimensional electron gases in In0.52Ga0.48As quantum wells, surrounded by In0.52Al0.48As barriers, where either one or two electric subbands are populated. Structural inversion asymmetry does not exist at low carrier density while at higher carrier densities (above (4–5) × 1011 cm−2), a finite spin splitting is observed. The spin orbit coupling coefficients (α) are determined from the power spectrum …
Technology Development & Design For 22 Nm Ingaas/Inp-Channel Mosfets, Paul J. Simmonds
Technology Development & Design For 22 Nm Ingaas/Inp-Channel Mosfets, Paul J. Simmonds
Paul J. Simmonds
Because of the low electron effective mass and the high resulting carrier velocities, we are developing InGaAs/InP MOSFETs for potential application in VLSI circuits at scaling generations beyond 22 nm. We will report device design, review gate dielectric growth processes, and describe in detail the development of process modules for fabrication of fully self-aligned enhancement-mode devices. Key design challenges include the effect of the low density of states upon drive current and the effect of the low carrier mass on vertical confinement. Target electrical parameters include ~5 mA/μm drive current and ~7 mS/μm2 transconductance. Key fabrication challenges include formation …
Quantum Transport In In0.75Ga0.25As Quantum Wires, P. J. Simmonds, F. Sfigakis, H. E. Beere, D. A. Ritchie, M. Pepper, D. Anderson, G. A.C. Jones
Quantum Transport In In0.75Ga0.25As Quantum Wires, P. J. Simmonds, F. Sfigakis, H. E. Beere, D. A. Ritchie, M. Pepper, D. Anderson, G. A.C. Jones
Paul J. Simmonds
In addition to quantized conductance plateaus at integer multiples of 2e2/h, the differential conductance G=dI/dV shows plateaus at 0.25(2e2/h) and 0.75(2e2/h) under applied source-drain bias in In0.75Ga0.25As quantum wires defined by insulated split gates. This observation is consistent with a spin-gap model for the 0.7 structure. Using a tilted magnetic field to induce Landau level crossings, the g factor was measured to be ~9 by the coincidence method. This material, with a mobility of 1.8×105 cm …
Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes
Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes
Paul J. Simmonds
Two-dimensional electron gases (2DEGs) were formed in undoped In0.75Al0.25As / In0.75Ga0.25As / In0.75Al0.25As quantum wells. The optimal growth temperature for this structure is 410°C, with peak 2DEG electron mobility and density values of μ = 221000 cm2/V s and n = 1.36 × 1011 cm−2 at 1.5 K. This electron mobility is equal to the highest previously published for these undoped structures but with a factor of 2 reduction in n. This has been achieved through the use of a significantly thinner InAlAs …
Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields
Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields
Paul J. Simmonds
Single photon detection was realized at a telecom wavelength with quantum dot resonant tunneling diodes grown on an InP substrate. The structure contains a AlAs/In0.53Ga0.47As/AlAs quantum well with InAs quantum dots grown on the top AlAs barrier. The single photon detection efficiency of the device under 1310 nm illumination was measured to be about 0.35% ± 0.07% with a dark count rate of 1.58×10-6 ns-1. This corresponds to an internal efficiency of 6.3%.
Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie
Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie
Paul J. Simmonds
The authors present a quantum dot (QD) based single photon detector operating at a fiber optic telecommunication wavelength. The detector is based on an AlAs/In0.53Ga0.47As/AlAs double-barrier resonant tunneling diode containing a layer of self-assembled InAs QDs grown on an InP substrate. The device shows an internal efficiency of about 6.3% with a dark count rate of 1.58 × 10−6 ns−1 for 1310 nm photons.
Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie
Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie
Paul J. Simmonds
The authors report the results of a detailed study of the effect of growth conditions, for molecular beam epitaxy, on the structural and optical properties of self-assembled InAs quantum dots (QDs) on In0.524Al0.476As. InAs QDs both buried in, and on top of, In0.524Al0.476As were analyzed using photoluminescence (PL) and atomic force microscopy. InAs QD morphology and peak PL emission wavelength both scale linearly with deposition thickness in monolayers (MLs). InAs deposition thickness can be used to tune QD PL wavelength by 170 nm/ML, over a range of almost 700 nm. Increasing growth …
Dynamics Of A Gravitational Billiard With A Hyperbolic Lower Boundary, Matthew L. Ferguson, B. N. Miller, M. A. Thompson
Dynamics Of A Gravitational Billiard With A Hyperbolic Lower Boundary, Matthew L. Ferguson, B. N. Miller, M. A. Thompson
Matthew L. Ferguson
Gravitational billiards provide a simple method for the illustration of the dynamics of Hamiltonian systems. Here we examine a new billiard system with two parameters, which exhibits, in two limiting cases, the behaviors of two previously studied one-parameter systems, namely the wedge and parabolic billiard. The billiard consists of a point mass moving in two dimensions under the influence of a constant gravitational field with a hyperbolic lower boundary. An iterative mapping between successive collisions with the lower boundary is derived analytically. The behavior of the system during transformation from the wedge to the parabola is investigated for a few …