Effect of Piezoelectric Filed on the Optical Properties of (311) A and (311) B Oriented InAlAs/InP Heterostructures

InAlAs alloy was grown by MOCVD on an InP (311) substrate with different polarities. Measurements of photoluminescence (PL) and photoreflectance (PR) were performed to study the impact of the V/III flux ratio. It is discovered that the PL line was shifted to a greater energy side with the increasing excitation power density, and no saturation was observed of its related PL intensity. It is a fingerprint of type II transition emission. However, the recombination of the type II interface showed a powerful dependence on AsH3 overpressure and substrate polarity. In fact, we have noted an opposite behavior of type II energy transition shift from A to B polarity substrate in respect to V/III ratio variation. PR signals corresponding to Franz-Keldysh Oscillation (FKO) were observed. The analysis of their period has allowed one to assess the value of the PZ field in the samples. PL-luminescence measurements were performed out as a function of temperature. PL peak energy, PL intensity, and half maximum full width show anomalous behaviors. Indicating the existence of localized carriers, they were ascribed to the energy potential modulation associated with the indium cluster formation and PZ field

Gold octahedra nanoparticles (Au_0.03 and Au_0.045): Synthesis and impact on marine clams Ruditapes decussatus

The increased use of gold nanoparticles (AuNPs) in several applications has led to a rise in concerns about their potential toxicity to aquatic organisms. In addition, toxicity of nanoparticles to aquatic organisms is related to their physical and chemical properties. In the present study, we synthesize two forms of gold octahedra nanoparticles (Au_0.03 and Au_0.045) in 1.3-propandiol with polyvinyl-pyrrolidone K30 (PVPK30) as capping agent using polyol process. Shape, size and optical properties of the particles could be tuned by changing the molar ratio of PVP K30 to metal salts. The anisotropy in nanoparticles shape shows strong localized surface plasmon resonance (SPR) in the near infrared region of the electromagnetic spectrum. Environmental impact of Oct-AuNPs was determined in the marine bivalve, Ruditapes decussatus exposed to different concentrations of Au_0.03 and Au_0.045. The dynamic light scattering showed the stability and resistance of Au_0.03 and Au_0.045 in the natural seawater. No significant modification in vg-like proteins, MDA level and enzymatic activities were observed in treated clams with Au_0.03 even at high concentration. In contrast, Au_0.045 induced superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST) activities, in a concentration dependent manner indicating defense against oxidative stress. Enhanced lipid peroxidation represented by malondialdehyde content confirmed oxidative stress of Au_0.045 at high concentration. These results highlight the importance of the physical form of nanomaterials on their interactions with marine organisms and provide a useful guideline for future use of Oct-AuNPs. In addition, Vitellogenin is shown not to be an appropriate biomarker for Oct-AuNPs contamination even at high concentration. We further show that Oct-AuNPs exhibit an important antioxidant response without inducing estrogenic disruption

Exploration of the Fluorescence Property of Acrylic Fibers Dyed with the Residues Extract of Juglans regia Barks

This study aims to check the fluorescence property of acrylic fabrics dyed with Juglans regia bark extract. Fluorescence measurements have been developed on the aqueous extract and acrylic samples. The extraction process was assisted by a microwave with the following conditions: a concentration of 5 g·L−1, a power of 850, a pH of 5 and an extraction duration of 4 min. Afterwards, the dyeing quality was assessed by measuring the color strength (K/S) and the photoluminescence intensity (PL) of acrylic fibers dyed at 350 W for 3 min, with the extract already prepared. The effect of certain factors (pH, power, concentration and duration of dyeing) on the dyeing process was also investigated. Subsequently, this process was optimized thanks to the surface response method in order to maximize the photoluminescence intensity of dyed acrylic fibers. Best dyeing properties were achieved at 500 W, pH 2 for 4 min. The results showed good washing fastness and acceptable light fastness

Stress Engineering of a Window Porous Silicon Layer based on Pseudo Substrate Suitable for III-V Monolithic Integration

Due to Silicon (Si) material abundance and specific properties, monolithic integration of III-V semiconductors on (Si) is of paramount importance for the next-generation in Optoelectronic devises. An alternative approach to lattice mismatched single silicon crystal substrates for heteroepitaxy is proposed. In this work, we have suggested a design of a compliant virtual substrate and we have explored the modulation of stress/lattice parameter of a window layer based on porous silicon pseudo-substrates allowing a defect free epitaxial growth. We prepared a silicon window layer with low porosity and variable thicknesses whose stress is modulated by the succession of several layers with gradual porosity. As a result, we evaluated the stress and the lattice parameter in compliant substrate before and after thermal annealing. The pores reorganization process was supported in Argon atmosphere at constant temperature (900 °C). The samples were studied morphologically by Field Emission scanning Electron Microscope (FE-SEM) and structurally by High Resolution X-Ray Diffraction (HR-XRD) and Nano-Raman

Effect of V/III ratio on the optical properties of (3 1 1)A and (3 1 1) B oriented InAlAs/InP heterostructures

InAlAs alloy were grown on a InP (3 1 1) substrate with different polarity, by metalorganic chemical vapor deposition (MOCVD) growth. Photoluminescence (PL) and Photoreflectance (PR) measurements have been carried out, in our samples, in order to study the V/III flux ratio effect in type-II heterostructures. It is found that, with increasing excitation power density, the PL line was shifted at higher energy side and no saturation of its associated PL intensity was observed. It is a fingerprint of type II transition emission. Yet, the type II interface recombination has shown a strong dependence on AsH3 overpressure and substrate polarity. Therefore, the arsenic overpressures (V/III) affect the piezoelectric (PZ) field and the As/P exchange in our investigated structures. Indeed, we have observed an opposite behavior of type II energy transition shift from A (Indium In face) to B (Phosphorus P face) polarity substrate in respect to V/III flow ratio variation. This fact has been explained as an atomic terminated surface (In or P) in InP substrate. In the other side, PR signals corresponding to Franz-Keldysh Oscillation (FKO) have been observed, in InAlAs/InP (3 1 1). The analysis of their period has allowed one to determine the value of the PZ field in the samples. This result enables us to extract the V/III ratio and the substrate polarity effect on the type II transition shift, in such heterostructures. Keywords: V/III flux ratio, MOCVD, Piezoelectric field, Franz-Keldysh Oscillation, Photoreflectance, Photoluminescenc

Theoretical analyses of the carrier localization effect on the photoluminescence of In-rich InGaAs layer grown on InP

The free buffer InGaAs/InP structure has been elaborated by Metal Organic Vapor Phase Epitaxy (MOVPE). High indium content is chosen to reduce the bandgap energy of the ternary material with direct bandgap to be pro-moted for Infrared optoelectronic devices. In this work, the temperature dependent photoluminescence (TDPL) analysis of In-rich InxGa1_xAs (x = 0.65: S-1, x = 0.661: S-2, and x = 0.667 S-3) samples is of the central focus. The S-shaped behavior recorded at low temperature range in the III-V ternary is quantitatively studied herein by Localized State Ensemble (LSE) model. A comparison between the semi-empirical evolution of luminescence versus temperature and our numerical simulation proves the adequacy of computational details, used in LSE model, in well reproducing the S-shape feature. The numerical simulation well matched with PL spectra proving that the localization phenomenon is stronger when increasing the Indium mole fraction. The clustering effect in In-rich structure seems to be beneficial for enhancing the carrier localization within InxGa1_xAs by localizing carriers from away extended defects that behave probably as non-radiative centers. This is indicative of the utmost importance of localization phenomenon in trapping carriers within localized states instead of dislocations and defects, owing to clustering of indium atoms

Systematic optical study of high-x InxGa1-xAs/InP structures for infrared photodetector applications

Optical and structural properties in high-x InxGa1-xAs (x > 0.65) samples with varying indium concentration grown on InP (1 00) substrate are reported. By increasing the indium fraction, it was found by the high-resolution X-ray diffraction (HR-XRD) study that the dislocation density in the InxGa1-xAs epitaxial layer significantly increased, and the surface quality deteriorated remarkably. Photoreflectance (PR) spectra show the presence of Franz-Keldysh Oscillations (FKOs) features above the InxGa1-xAs energy bandgap. The strain-induced electric field is then estimated directly from the FKOs periods. Temperature-dependent photoluminescence (TDPL) measurements from 10 K to 300 K showed carrier locations (S-shape). This abnormal behavior is due to the dislocation density associated with fluctuations in the indium concentration. A quasi-stationary rate equation model for the temperature-dependent luminescence spectra of the localized state material system is proposed to interpret the band gap emission process quantitatively. Low-temperature (10 K) time-resolved PL measurements show the increase of lifetime with increasing the indium concentration. Yet, the addition of only 1.7% of indium concentration results in a strong enhancement of PL lifetime by ~ 80%.& nbsp;All these results reveal a more precise picture of the localization and recombination mechanisms of photo-generated carriers in the InGaAs layer, which could be the crucial factors in controlling the performance of high indium content InGaAs SWIR detector