A5061928282- Semiconductor Quantum Structures and Devices
- GaN-based semiconductor devices and materials
- ZnO doping and properties
- Advanced Semiconductor Detectors and Materials
- Quantum Dots Synthesis And Properties
- Semiconductor materials and devices
- Ga2O3 and related materials
- Semiconductor Lasers and Optical Devices
- Chalcogenide Semiconductor Thin Films
- Gas Sensing Nanomaterials and Sensors
- Spectroscopy and Laser Applications
- Plasmonic and Surface Plasmon Research
- Copper-based nanomaterials and applications
- solar cell performance optimization
- Electronic and Structural Properties of Oxides
- Nanowire Synthesis and Applications
- Metamaterials and Metasurfaces Applications
- Semiconductor materials and interfaces
- Atmospheric Ozone and Climate
- Perovskite Materials and Applications
- Thermal Radiation and Cooling Technologies
- Optical Coatings and Gratings
- Photonic Crystals and Applications
- Acoustic Wave Resonator Technologies
- Advanced Chemical Physics Studies
Universidad Politécnica de Madrid
2015-2024
Institut für Sozialforschung und Sozialwirtschaft
2018
Universidad Complutense de Madrid
2017
Institute of Microelectronics
2016
Binghamton University
2015
Centre National de la Recherche Scientifique
2011
Université Côte d'Azur
2011
Universitat de València
2007
The Ohio State University
1998-2002
Universidad Autónoma de Madrid
1996-1997
Abstract Tackling the interfacial loss in emerged perovskite‐based solar cells (PSCs) to address synchronously carrier dynamics and environmental stability, has been of fundamental viable importance, while technological hurdles remain not only creating such mediator, but subsequent embedding active layer. This article reports a strategy hydrophobic fluorinated‐gold‐clusters (FGCs) for highly efficient stable PSCs. The p‐type semiconducting feature enables FGC mediator improve by reducing...
The Sb-induced changes in the optical properties of GaAsSb-capped InAs/GaAs quantum dots (QDs) are shown to be strongly correlated with structural changes. observed redshift photoluminescence emission is follow two different regimes. In first regime, Sb concentrations up $\ensuremath{\sim}12\mathrm{%}$, wavelength shifts $\ensuremath{\sim}1280\text{ }\text{nm}$ a large enhancement luminescence characteristics. A analysis at atomic scale by cross-sectional scanning tunneling microscopy shows...
N-Schottky and p+–n GaN junctions are currently used for different technologies. A comparison of the deep levels found throughout entire band gap n-GaN grown by metal-organic chemical vapor deposition under both configurations is presented. Both level optical spectroscopy transient measurements allowing observation majority minority carrier traps. Deep at Ec−Et=0.58–0.62, 1.35, 2.57–2.64, 3.22 eV observed diode configurations, with concentrations in ∼1014–1016 cm−3 range. The 0.58–0.62...
Differential postgrowth hydrogen passivation of deep levels in n–GaN grown by metal-organic chemical vapor deposition has been directly observed means both level transient spectroscopy and optical spectroscopy. Two found at Ec−Et=0.62 1.35 eV show strong H effects, with their concentrations decreasing a factor ⩾30 ∼14, respectively. The decrease the 0.62 trap concentration together its correlation presence Mg is consistent Mg–H complex formation. A band closely spaced Ec−Et=2.64–2.80 narrows...
Schottky photodiodes based on Au-ZnMgO/sapphire are demonstrated covering the spectral region from 3.35 to 3.48 eV, with UV/VIS rejection ratios up ∼105 and responsivities as high 185 A/W. Both ratio responsivity shown be largely enhanced by presence of an internal gain mechanism, which compensated films become highly conductive a result illumination. This causes large increase in tunnel current through barrier, yielding gains that function incident photon flux.
The impact of rapid thermal annealing on the optical emission GaInNAs/GaAs quantum wells (QWs) grown by molecular beam epitaxy with high In and N content is shown to be highly dependent crystal structure QWs, as determined transmission electron microscopy. Due presence higher concentrations nonradiative recombination centers, temperature required obtain maximum photoluminescence for QW strong structural modulation upper interface [at onset three-dimensional (3D) growth], intermediate...
The effect of growth regime on the deep level spectrum n-GaN using molecular-beam epitaxy (MBE) was investigated. As Ga/N flux ratio decreased towards Ga-lean conditions, concentration two acceptor-like levels, at Ec−3.04 and 3.28 eV, increased from 1015 to 1016 cm−3 causing carrier compensation in these films. Thus, traps behaved as dominant compensating centers MBE n-GaN. Furthermore, increase trap also strongly correlated with degradation both surface morphology bulk electron mobility...
The origin of the modified optical properties InAs/GaAs quantum dots (QD) capped with a thin GaAs1−xSbx layer is analyzed in terms band structure. To do so, size, shape, and composition QDs capping are determined through cross-sectional scanning tunnelling microscopy used as input parameters an 8 × k·p model. As Sb content increased, there two competing effects determining carrier confinement oscillator strength: increased QD height reduced strain on one side QD-capping valence offset other....
Light polarization-sensitive UV photodetectors (PSPDs) using non-polar a-plane ZnMgO/ZnO multiple quantum wells grown both on sapphire and ZnO substrates have been demonstrated. For the PSPDs with anisotropic biaxial in-plain strain, responsivity absorption edge shifts by ΔE ∼ 21 meV between light polarized perpendicular (⊥) parallel (||) to c-axis, maximum (R) contrast is (R⊥/R||)max 6. ZnO, strain-free wells, 40 5. These polarization sensitivities explained in terms of excitonic...
We have developed a method to grow and characterize the state of art non-polar ZnO/(Zn,Mg)O multi-quantum wells on m-plane ZnO substrates as prerequisite for applications based intersubband transitions. The epilayer interfaces exhibit low roughness, layer thickness remains constant within one monolayer in these heterostructures. optical properties been studied UV IR domains by means photoluminescence absorption experiments, respectively. In UV, is very well described an excitonic transition,...
The carrier capture kinetics of the Ec—0.59 eV and Ec—0.91 electron traps found in molecular beam epitaxy (MBE)-grown n-GaN have been determined by means deep level transient spectroscopy (DLTS). 0.59 trap does not show behaviour either ideal point defects or line defects. In contrast, 0.91 displays linearly arranged interacting defects, which generate a time-dependent local Coulombic potential with characteristic time constant ≈ 8.6 μs.
A systematic analysis of the deep level spectrum in lower half bandgap Au–Zn1−xMgxO (0.056<x<0.18) Schottky diodes is presented. Two levels are observed at Ev+580 and Ev+280 meV regardless energy with trap concentrations linearly increasing Mg content. The concentration becomes as high 1.01×1018 cm−3 18% Mg, partially compensating films causing a decrease from 8.02×1016 to 1.27×1016 net electron an increase by three orders magnitude diode series resistance due trapping.
High quality 1 μm thick a-plane MgxZn1−xO layers were produced by molecular beam epitaxy with Mg contents higher than 50%. Resonant Rutherford backscattering spectrometry combined ion channeling revealed a uniform growth in both composition and atomic order. The lattice-site location of Mg, Zn O elements was determined independently, proving the substitutional behaviour Zn-sites wurtzite lattice. X-Ray diffraction pole figure analysis also confirms absence phase separation. Optical...
The photoluminescence efficiency of GaAsSb-capped InAs/GaAs type II quantum dots (QDs) can be greatly enhanced by rapid thermal annealing while preserving long radiative lifetimes which are ∼20 times larger than in standard GaAs-capped QDs. Despite the reduced electron-hole wavefunction overlap, type-II samples more efficient type-I counterparts terms luminescence, showing a great potential for device applications. Strain-driven In-Ga intermixing during is found to modify QD shape and...
This paper reports on the demonstration of quantum cascade detectors (QCDs) based ZnO/ZnMgO wells (QWs) grown by molecular beam epitaxy an m-plane ZnO substrate. The TM-polarized intersubband absorption is peaked at a 3 μm wavelength. sample has been processed in form square mesas with sizes ranging from 10 × μm2 up to 100 μm2. I-V characteristics reveal that 86% 260 devices are operational and surface leakage current negligible room temperature, which not case 77 K. photocurrent...
The effect of the capping process on morphology InAs/GaAs quantum dots (QDs) by using different GaAs-based layers (CLs), ranging from strain reduction to compensating layers, has been studied transmission microscopic techniques. For this, we have measured simultaneously height and diameter in buried uncapped QDs covering populations hundreds that are statistically reliable. First, QD population evolves all cases a pyramidal shape into more homogenous distribution with spherical-dome shape,...
Multi-junction solar cells made by assembling semiconductor materials with different bandgap energies have hold the record conversion efficiencies for many years and are currently approaching 50%. Theoretical efficiency limits make use of optimum designs right lattice constant-bandgap energy combination, which requires a 1.0-1.15 eV material lattice-matched to GaAs/Ge. Nevertheless, lack suitable is hindering achievement predicted efficiencies, since only candidates were up now complex...
Transparent conducting oxides (TCOs) are widely used in applications from solar cells to light emitting diodes. Here, we show that the metal organic chemical vapor deposition (MOCVD)-grown, rock-salt CdZnO ternary, has excellent potential as a TCO. To assess this compound, use combination of infrared reflectance and ultraviolet-visible absorption spectroscopies, together with Hall effect, determine its optical electrical transport characteristics. It is found incorporation Zn produces an...
The ZnO-based heterostructures are predicted to be promising candidates for optoelectronic devices in the infrared and terahertz (THz) spectral domains owing their intrinsic material properties. Specifically, large ZnO LO-phonon energy reduces thermally activated scattering, which is greatly improve temperature performance of THz quantum cascade lasers. However, date, no experimental observation intersubband emission from has been reported. Here, we report electroluminescence ZnO/MgxZn1–xO...
Second-harmonic generation from λ=1.06 μm fundamental light has been measured in both evaporated and spin-coated films of trinitro-substituted subphthalocyanines. Ordering these noncentrosymmetric molecules with the dipole moment perpendicular to film face achieved either by deposition process (evaporated samples) or corona poling (spin-coated samples). The second-order susceptibilities χ31(2)=2.36×10−9 esu (for vacuum χ31(2)=9.62×10−10–1.14×10−9 poled have determined comparison an X-cut...
A procedure to quantitatively analyse the relationship between wetting layer (WL) and quantum dots (QDs) as a whole in statistical way is proposed. As we will show manuscript, it allows determining, not only proportion of deposited InAs held WL, but also average In content inside QDs. First, amount measured for calibration three different WL structures without QDs by two methodologies: strain mappings high-resolution transmission electron microscopy images compositional with ChemiSTEM x-ray...