A5052408119- GaN-based semiconductor devices and materials
- ZnO doping and properties
- Ga2O3 and related materials
- Semiconductor Quantum Structures and Devices
- Perovskite Materials and Applications
- Thermal Radiation and Cooling Technologies
- Advanced Fiber Laser Technologies
- Metal and Thin Film Mechanics
- Quantum Dots Synthesis And Properties
- Mechanical and Optical Resonators
- Photonic and Optical Devices
- Nanowire Synthesis and Applications
- Metamaterials and Metasurfaces Applications
- Phase-change materials and chalcogenides
- Thermal properties of materials
- Nonlinear Optical Materials Studies
- Plasmonic and Surface Plasmon Research
- 2D Materials and Applications
- Electronic and Structural Properties of Oxides
- CCD and CMOS Imaging Sensors
- Solar Thermal and Photovoltaic Systems
- Solid-state spectroscopy and crystallography
- Photocathodes and Microchannel Plates
- Chalcogenide Semiconductor Thin Films
- Gas Sensing Nanomaterials and Sensors
University of Southampton
2021-2025
King Abdullah University of Science and Technology
2011-2023
Hydrogen production via photoelectrochemical water-splitting is a key source of clean and sustainable energy. The use one-dimensional nanostructures as photoelectrodes desirable for applications due to the ultralarge surface areas, lateral carrier extraction schemes, superior light-harvesting capabilities. However, unavoidable states nanostructured materials create additional charge trapping centers energy barriers at semiconductor-electrolyte interface, which severely reduce...
Abstract Two dimensional inorganic–organic hybrid perovskites (2D perovskites) suffer from not only quantum confinement, but also dielectric hindering their application perspective in devices involving the conversion of an optical input into current. In this report, we theoretically predict that extremely low exciton binding energy can be achieved 2D by using high dielectric-constant organic components. We demonstrate (HOCH 2 CH NH 3 ) PbI 4 , whose material has a constant 37, confinement is...
A droop-free nitride light-emitting diode (LED) with the capacity to operate beyond "green gap" has been a subject of intense scientific and engineering interest. While several properties nanowires on silicon make them promising for use in LED development, high aspect ratio individual their laterally discontinuous features limit phonon transport device performance. Here, we report monolithic integration metal heat-sink InGaN/GaN quantum-disks-in-nanowire LEDs emitting at ∼710 nm. The...
Enhanced ultraviolet (UV) photodetectors (PDs) with high responsivity comparable to that of visible and infrared are needed for commercial applications. n-Type ZnO nanotubes (NTs) high-quality optical, structural, electrical properties on a p-type Si(100) substrate successfully fabricated by pulsed laser deposition (PLD) produce UV PD responsivity, the first time. We measure current-voltage characteristics device under dark illuminated conditions demonstrated stability (that reaches ∼101.2 A...
We investigate the effects of V-pits on optical properties a state-of-the-art, highly efficient, blue InGaN/GaN multi-quantum-well (MQW) light-emitting diode (LED) with high internal quantum efficiency (IQE) >80%. The LED is structurally enhanced by incorporating pre-MQW InGaN strain-relief layer low InN content and patterned sapphire substrate. For comparison, conventional (unenhanced) MQW (with an IQE 46%) grown under similar conditions was subjected to same measurements. Scanning...
Understanding defect chemistry, particularly ion migration, and its significant effect on the surface's optical electronic properties is one of major challenges impeding development hybrid perovskite-based devices. Here, using both experimental theoretical approaches, we demonstrated that surface layers perovskite crystals may acquire a high concentration positively charged vacancies with complementary negatively halide ions pushed to surface. This charge separation near generates an...
Significant internal quantum efficiency (IQE) enhancement of GaN/AlGaN multiple wells (MQWs) emitting at ~350 nm was achieved via a step well (QW) structure design. The MQW structures were grown on AlGaN/AlN/sapphire templates by metal-organic chemical vapor deposition (MOCVD). High resolution x-ray diffraction (HR-XRD) and scanning transmission electron microscopy (STEM) performed, showing sharp interface the MQWs. Weak beam dark field imaging conducted, indicating similar dislocation...
The photoinduced entropy of InGaN/GaN p-i-n nanowires was investigated using temperature-dependent (6–290 K) photoluminescence. We also analyzed the photocarrier dynamics in InGaN active regions time-resolved An increasing trend amount generated system above 250 K observed, while we observed an oscillatory below that stabilizes between 200 and K. Strong exciton localization indium-rich clusters, carrier trapping by surface defect states, thermodynamic effects were examined related to...
Abstract We demonstrate the high structural and optical properties of In x Ga 1−x N epilayers (0 ≤ 23) grown on conductive transparent ("Equation missing"<!-- image only, no MathML or LaTex -->01)-oriented β-Ga 2 O 3 substrates using a low-temperature GaN buffer layer rather than AlN layer, which enhances quality stability crystals compared to those (100)-oriented . Raman maps show that 2″ wafer is relaxed uniform. Transmission electron microscopy (TEM) reveals dislocation density reduces...
GaN/AlGaN multiple quantum wells (MQWs) are grown on a 2¯01-oriented β-Ga2O3 substrate. The optical and structural characteristics of the MQW structure compared with those similar sapphire. Scanning transmission electron microscopy atomic force images show that exhibits higher crystalline quality well-defined when to X-ray diffraction rocking curve photoluminescence excitation analyses confirm lower density dislocation defects in sample A detailed analysis time-integrated time-resolved...
AlGaN/AlGaN multi-quantum-wells (MQW) with AlN-rich grains have been grown by metal organic chemical vapor deposition. The are observed to strong excitonic localization characteristics that affected their sizes. tendency confine excitons progressively intensifies increasing grain boundary area. Photoluminescence results indicate the MQW a dominant effect on peak energy of near-bandedge emission at temperatures below 150 K, properties becoming evident beyond K. Cathodoluminescence maps reveal...
One-dimensional (1D) structures-based UV-light-emitting diode (LED) has immense potential for next-generation applications. However, several issues related to such devices must be resolved first, as expensive material and growth methods, complicated fabrication process, efficiency droop, unavoidable metal contamination due catalyst that reduces device efficiency. To overcome these obstacles, we have developed a novel method obtaining high-quality hexagonal, well-defined, vertical 1D Gd-doped...
Optical Solar Reflectors (OSRs) combine low solar radiation absorption (α) and high broadband infrared emissivity (ε) are applied to the external surface of spacecraft for its thermal management. Bulk glass OSR tiles incumbent, but ultra-lightweight thin-film flexible coatings raising considerable interest both space terrestrial radiative cooling applications. In this work, a genetic algorithm combined with transfer matrix method is used design optimization multimaterial OSRs cooling. The...
High-performance programmable silicon photonic circuits are considered to be a critical part of next-generation architectures for optical processing, quantum circuits, and neural networks. Low-loss phase-change materials (PCMs) offer promising route toward nonvolatile free-form control light. Here, we exploit the direct-write digital patterning waveguides using layers PCM Sb2Se3 with thickness values from 20 100 nm, demonstrating scaling induced phase shift ability strongly increase effect...
Abstract In this work, indium (In) was introduced as a surfactant during growth of high temperature GaN quantum barriers (QBs) and interlayer InGaN/GaN green LEDs. A reference LED grown without In-surfactant also included for comparison. Results suggested that the improved by introducing In-surfactant, especially interlayer. The morphology interlayer, hence allowed it to serve good surface LED. Moreover, showed lowest full width at half maximum each x -ray diffraction satellite peak when in...
Optically and vibrationally resonant nanophotonic devices are of particular importance for their ability to enhance optomechanical interactions, with applications in nanometrology, sensing, nano-optical control light, optomechanics. Here, the optically excitation detection gigahertz vibrational modes demonstrated a nanoscale metasurface array fabricated on suspended SiC membrane. With design main optical be those individual metamolecules, achieved by making use direct mechanisms coupling....
High-performance programmable silicon photonic circuits are considered to be a critical part of next generation architectures for optical processing, quantum and neural networks. Low-loss phase change materials (PCMs) offer promising route towards non-volatile free-form control light. Here, we exploit direct-write digital patterning waveguides using layers the PCM Sb$_2$Se$_3$ with thickness up 100 nm, demonstrating ability strongly increase effect per pixel compared previous implementations...
We explore the effect of subwell centers and related carrier dynamics mechanisms in dislocation-free DUV AlGaN/AlGaN multiple quantum wells (MQWs) homoepitaxially grown on an AlN substrate. Cross-sectional imaging energy-dispersive X-ray compositional analyses using scanning transmission electron microscopy (STEM) reveal epitaxial layers very high crystalline quality, as well ultrathin Al-rich subquantum barrier at interface between barriers. Carrier dynamic studied by power-...
There has been a relentless pursuit of transverse electric (TE)-dominant deep ultraviolet (UV) optoelectronic devices for efficient surface emitters to replace the environmentally unfriendly mercury lamps. To date, use ternary AlGaN alloy inevitably led magnetic (TM)-dominant emission, an approach that is facing roadblock. Here, we take entirely different utilizing binary GaN compound semiconductor in conjunction with ultrathin quantum disks (QDisks) embedded AlN nanowires (NWs). The growth...
The degree of enhancement in radiative recombination ensembles semiconductor nanowires after chemical treatment is quantified within a derived limit by correlating the energy released during photoemission processes light–matter reaction and effective carrier lifetimes. It argued that usage surface velocity or saturation current density as passivation metrics assess effectiveness does not provide strict universal theoretical bounds which can be confined. In this context, model developed study...
Heavy reliance on extensively studied AlGaN based light emitting diodes (LEDs) to replace environmentally hazardous mercury ultraviolet (UV) lamps is inevitable. However, external quantum efficiency (EQE) for deep UV emitters remains poor. Dislocation induced nonradiative recombination centers and poor electron-hole wavefunction overlap due the large polarization field confined stark effect (QCSE) in "Al" rich are some of key factors responsible EQE. In addition, transverse electric...
In this letter, two empirical equations are presented for the calculation of excess noise factor an avalanche photodiode single carrier multiplication including dead space effect. The first is equation calculating when approaches infinity as a function parameters that describe degree second can be used to find minimum value any effect completely dominant, so called "deterministic" limit. This agrees with theoretically known multiplications less than or equal two.
Nano-optomechanical metasurface arrays (MSAs) are a class of two-dimensional metamaterials with periodic subwavelength structures which mechanically actuated by electromagnetic waves. In this work we demonstrate GHz optomechanical resonances in dielectric silicon carbide (SiC) array.