A5002693114- Semiconductor Quantum Structures and Devices
- Quantum and electron transport phenomena
- Spectroscopy and Laser Applications
- Advanced Semiconductor Detectors and Materials
- Semiconductor materials and devices
- Semiconductor Lasers and Optical Devices
- Photonic and Optical Devices
- Terahertz technology and applications
- Silicon Nanostructures and Photoluminescence
- Advancements in Semiconductor Devices and Circuit Design
- X-ray Diffraction in Crystallography
- Chalcogenide Semiconductor Thin Films
- Crystallization and Solubility Studies
- Physics of Superconductivity and Magnetism
- Laser-Matter Interactions and Applications
- Semiconductor materials and interfaces
- Quantum optics and atomic interactions
- Quantum Information and Cryptography
- Mechanical and Optical Resonators
- Quantum Dots Synthesis And Properties
- Spectroscopy and Quantum Chemical Studies
- GaN-based semiconductor devices and materials
- Silicon and Solar Cell Technologies
- Advanced Chemical Physics Studies
- Magnetic properties of thin films
University of Surrey
2015-2024
University of Salford
2019
Hubei University
2019
London Centre for Nanotechnology
2015-2018
University College London
2015-2018
Radboud University Nijmegen
2017
FELIX Laboratory
2017
South East Physics Network
2011
Institute for Atomic and Molecular Physics
1994-2008
Heriot-Watt University
1992-1997
Spin states in semiconductors provide exceptionally stable and noise-resistant environments for qubits, positioning them as optimal candidates reliable quantum computing technologies. The proposal to use nuclear electronic spins of donor atoms silicon, introduced by Kane 1998, sparked a new research field focused on the precise individual impurity devices, utilising scanning tunnelling microscopy ion implantation. This roadmap article reviews advancements 25 years since Kane's proposal,...
Pump-probe transmission experiments have been performed on PbSe above the fundamental absorption edge near 4 \ensuremath{\mu}m in temperature range 30 to 300 K, using Dutch ps free-electron laser. For temperatures below 200 K and carrier densities threshold for stimulated emission, recombination represents most efficient mechanism with relatively fast kinetics 50--100-ps regime, good agreement earlier reports of photoluminescent emission. Above this Auger dominates, coefficient C is...
We report the direct observation of a bottleneck in electron cooling wide GaAs quantum wells. Intersubband lifetimes \ensuremath{\tau} and their dependence on intensity, lattice temperature ${\mathrm{T}}_{\mathrm{L}}$ , well width have been measured using ps excite-probe technique wells with subband separation less than longitudinal optical (LO) phonon energy. Above an about ${\mathrm{T}}_{\mathrm{e}}$ =35 K lifetime depends is determined by LO-phonon emission. Below this acoustic phonons...
One of the great successes quantum physics is description long-lived Rydberg states atoms and ions. The Bohr model equally applicable to donor impurity in semiconductor physics, where conduction band corresponds vacuum, loosely bound electron orbiting a singly charged core has hydrogen-like spectrum according usual Bohr–Sommerfeld formula, shifted far-infrared because small effective mass high dielectric constant. Manipulation free ions by single multiphoton processes been tremendously...
Laboratory spectroscopy of atomic hydrogen in a magnetic flux density 105 T (1 gigagauss), the maximum observed on high-field white dwarfs, is impossible because practically available fields are about thousand times less. In this regime, cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities silicon up to equivalent field, which scaled 32.8 by effective mass dielectric constant. The reproduce theory free hydrogen, with quadratic Zeeman...
Photogalvanic effects are observed and investigated in wurtzite (0001)-oriented GaN/AlGaN low-dimensional structures excited by terahertz radiation. The shown to represent linear quantum ratchets. Experimental theoretical analysis exhibits that the photocurrents related lack of an inversion center GaN-based heterojunctions.
Under oblique incidence of circularly polarized infrared radiation the spin-galvanic effect (SGE) has been unambiguously observed in (001)-grown n-type GaAs quantum well structures absence any external magnetic field. Resonant intersubband transitions have obtained making use tunability free-electron laser FELIX. A microscopic theory SGE for developed, which is good agreement with experimental findings.
We report Larmor precession in bulk InSb observed the time domain from $77\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The optically oriented polarization precesses coherently even at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. inferred Zeeman spin splitting is strongly nonparabolic, and electron $g$ factor $({g}^{*})$ good agreement with $\mathbf{k}∙\mathbf{p}$ theory (provided we take only dilational contribution to change energy...
Background: Cognitive Muscular TherapyTM (CMT) is an integrated behavioural intervention developed for knee osteoarthritis.CMT teaches patients to reconceptualise the condition, integrates muscle biofeedback and aims reduce overactivity, both in response pain during daily activities.This nested qualitative study explored patient physiotherapist perspectives experiences of CMT.Methods: Five physiotherapists were trained follow a well-defined protocol then delivered CMT at least two with...
Abstract The ability to control dynamics of quantum states by optical interference, and subsequent electrical read-out, is crucial for solid state technologies. Ramsey interference has been successfully observed spins in silicon nitrogen vacancy centres diamond, orbital motion InAs dots. Here we demonstrate terahertz excitation, manipulation destruction via wavepackets Si:P with read-out. We show milliradian over the wavefunction phase two-level system formed 1 s 2 p states. results have...
Abstract Spin states in semiconductors provide exceptionally stable and noise-resistant environments for qubits, positioning them as optimal candidates reliable quantum computing technologies. The proposal to use nuclear electronic spins of donor atoms silicon, introduced by Kane 1998, sparked a new research field focused on the precise individual impurity devices, utilising scanning tunnelling microscopy ion implantation. This roadmap article reviews advancements 25 years since Kane’s...
Dilute nitrogen alloys of InSb exhibit strong band gap bowing with increasing composition, shifting the absorption edge to longer wavelengths. The conduction dispersion also has an enhanced nonparabolicity, which suppresses Auger recombination. We have measured lifetimes in 11 and 15 μm edges using a time-resolved pump-probe technique. find be at room temperature than equivalent Hg1−yCdyTe same quasi-Fermi level separation. results are explained modified k⋅p Hamiltonian explicitly includes...
Landau-level lifetimes are determined from saturation cyclotron resonance measurements on an InAs/GaSb double heterojunction using a picosecond far-infrared free-electron laser. Strong nonparabolicity of the conduction band truncates equidistant ladder, and is achieved at all wavelengths. The show minima N\ensuremath{\Elzxh}${\mathrm{\ensuremath{\omega}}}_{\mathit{c}}$=\ensuremath{\Elzxh}${\mathrm{\ensuremath{\omega}}}_{\mathrm{LO}}$, direct observation magnetophonon effect. Observed due to...
Room-temperature pump–probe transmission experiments have been performed on an arsenic-rich InAs/InAs1−xSbx strained layer superlattice (SLS) above the fundamental absorption edge near 10 μm, using a ps far-infrared free-electron laser. Measurements show complete bleaching at excitation frequency, with recovery times which are found to be strongly dependent pump photon energy. At high excited carrier densities, corresponding energy and interband coefficient, recombination is dominated by...
Dilute nitrogen alloys of InSb exhibit extremely strong band gap bowing with composition that has been associated anticrossing between the localized resonant states within conduction and extended itself. This also results in dispersion having an enhanced nonparabolicity. We have measured electron effective mass near by cyclotron resonance InNxSb1−x absorption edge 15 μm, using pulsed fields up to 150 T. The directly demonstrate quantitatively confirm increase versus x predicted for a tight...
Fourier transform infrared absorption measurements are presented from the dilute nitride semiconductor GaNSb with nitrogen incorporations between 0.2% and 1.0%. The divergence of transitions valence band to E− E+ can be seen increasing incorporation, consistent theoretical predictions. structure has been modeled using a five-band k∙p Hamiltonian anticrossing fitting obtained level 0.78eV above maximum coupling parameter 2.6eV.
The structural and optoelectronic properties in GaNxSb1−x alloys (0⩽x<0.02) grown by molecular-beam epitaxy on both GaSb substrates AlSb buffer layers GaAs are investigated. High-resolution x-ray diffraction (XRD) reciprocal space mapping indicate that the epilayers of high crystalline quality alloy composition is found to be independent substrate, for identical growth conditions. band gap GaNSb decrease with increasing nitrogen content from absorption spectroscopy. Strain-induced...
Photoluminescence (PL) has been observed from dilute InNxAs1−x epilayers grown by molecular-beam epitaxy. The PL spectra unambiguously show band gap reduction with increasing N content. variation of the temperature is indicative carrier detrapping localized to extended states as increased. redshift free exciton peak content and reproduced anticrossing model, implemented via a (5×5)k∙p Hamiltonian.
The temperature dependence of the electron spin $g$ factor in GaAs is investigated experimentally and theoretically. Experimentally, was measured using time-resolved Faraday rotation due to Larmor precession spins range between 4.5 190 K. experiment shows an almost linear increase value with temperature. This result good agreement other measurements based on photoluminescence quantum beats Kerr up room experimental data are described theoretically taking into account a diminishing...
Abstract Single impurities in insulators are now often used for quantum sensors and single photon sources, while nanoscale semiconductor doping features being constructed electrical contacts technology devices, implying that new methods sensitive, non‐destructive imaging of single‐ or few‐atom structures needed. X‐ray fluorescence (XRF) can provide with chemical specificity, comprising as few 100 000 atoms have been detected without any need specialized destructive sample preparation....
The temperature dependence of the threshold current InGaAsSb∕AlGaAsSb compressively strained lasers is investigated by analyzing spontaneous emission from working laser devices through a window formed in substrate metallization and applying high pressures. It found that nonradiative recombination accounts for 80% at room responsible sensitivity. authors suggest Auger involving hot holes suppressed these because spin-orbit splitting energy larger than band gap, but other processes persist are...
Photoluminescence (PL) has been used as a means of unambiguously observing band gap reduction in InNAs epilayers grown by molecular beam epitaxy. The observed redshift room temperature emission function nitrogen concentration is agreement with the predictions anticrossing (BAC) model, implemented model parameters derived from tight-binding calculations. dependence certain samples exhibits signature non-Varshni-like behavior indicative electron trapping nitrogen-related localized states below...