Strain Effects in InP Dots in between Barriers of GaInP

1995 ◽  
Vol 417 ◽  
Author(s):  
Mats-Erik Pistol ◽  
Srinivasan Anand ◽  
Niclas Carlsson ◽  
Dan Hessman ◽  
Lars Landin ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Strain Tensor ◽  
Blue Shift ◽  
Deformation Potential ◽  
Emission Energy ◽  
Surrounding Matrix ◽  
Cap Layer ◽  
Deformation Potential Theory ◽  
Strong Blue Shift ◽  
Good Agreement

AbstractWe have investigated the photoluminescence emission energy of InP dots as a function of cap layer thickness. We find a strong blue-shift with increasing cap layer thickness. The strain tensor in the dot as well as in the surrounding matrix has been modelled using finite element methods and the band-gap has been calculated using deformation potential theory. We find good agreement between calculation and experiment. For uncapped dots we find that the emission energy is lower than for biaxially strained InP, and is indeed close to unstrained InP.

scholarly journals Photoreflectance and Raman Study of Surface Electric States on AlGaAs/GaAs Heterostructures

2016 ◽  
Vol 2016 ◽  
pp. 1-8
Author(s):  
Luis Zamora-Peredo ◽  
Leandro García-González ◽  
Julián Hernández-Torres ◽  
Irving E. Cortes-Mestizo ◽  
Víctor H. Méndez-García ◽  
...  
Keyword(s):  
Electric Field ◽  
Penetration Depth ◽  
Layer Thickness ◽  
Surface Passivation ◽  
Electronic States ◽  
Cap Layer ◽  
Raman Study ◽  
Surface Electric Field ◽  
532 Nm ◽  
Good Agreement

Photoreflectance (PR) and Raman are two very useful spectroscopy techniques that usually are used to know the surface electronic states in GaAs-based semiconductor devices. However, although they are exceptional tools there are few reports where both techniques were used in these kinds of devices. In this work, the surface electronic states on AlGaAs/GaAs heterostructures were studied in order to identify the effect of factors like laser penetration depth, cap layer thickness, and surface passivation over PR and Raman spectra. PR measurements were performed alternately with two lasers (532 nm and 375 nm wavelength) as the modulation sources in order to identify internal and surface features. The surface electric field calculated by PR analysis decreased whereas the GaAs cap layer thickness increased, in good agreement with a similar behavior observed in Raman measurements (IL-/ILOratio). When the heterostructures were treated by Si-flux, these techniques showed contrary behaviors. PR analysis revealed a diminution in the surface electric field due to a passivation process whereas theIL-/ILOratio did not present the same behavior because it was dominated by the depletion layers width (cap layer thickness) and the laser penetration depth.

scholarly journals Investigations on the Optical Properties of InGaN/GaN Multiple Quantum Wells with Varying GaN Cap Layer Thickness

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiaowei Wang ◽  
Feng Liang ◽  
Degang Zhao ◽  
Zongshun Liu ◽  
Jianjun Zhu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Quantum Wells ◽  
Layer Thickness ◽  
Stark Effect ◽  
Chemical Vapor ◽  
Multiple Quantum ◽  
Three Samples ◽  
Measurement Results ◽  
Cap Layer ◽  
The Difference

Abstract Three InGaN/GaN MQWs samples with varying GaN cap layer thickness were grown by metalorganic chemical vapor deposition (MOCVD) to investigate the optical properties. We found that a thicker cap layer is more effective in preventing the evaporation of the In composition in the InGaN quantum well layer. Furthermore, the quantum-confined Stark effect (QCSE) is enhanced with increasing the thickness of GaN cap layer. In addition, compared with the electroluminescence measurement results, we focus on the difference of localization states and defects in three samples induced by various cap thickness to explain the anomalies in room temperature photoluminescence measurements. We found that too thin GaN cap layer will exacerbates the inhomogeneity of localization states in InGaN QW layer, and too thick GaN cap layer will generate more defects in GaN cap layer.

scholarly journals Luminescent Characteristics of InGaAsP/InP Multiple Quantum Well Structures by Impurity-Free Vacancy Disordering

2001 ◽  
Vol 692 ◽  
Author(s):  
J. Zhao ◽  
X. D. Zhang ◽  
Z. C. Feng ◽  
J. C. Deng ◽  
P. Jin ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Band Gap ◽  
Annealing Temperature ◽  
Multiple Quantum Well ◽  
Blue Shift ◽  
Multiple Quantum ◽  
Quantum Well Structures ◽  
Cladding Layer ◽  
Cap Layer ◽  
Free Vacancy

AbstractInGaAsP/InP multiple quantum wells have been prepared by Impurity-Free Vacancy Disordering (IFVD). The luminescent characteristics was investigated using photoluminescence (PL) and photoreflectance (PR), from which the band gap blue shift was observed. Si3N4, SiO2 and SOG were used for the dielectric layer to create the vacancies. All samples were annealed by rapid thermal anne aling (RTA). The results indicate that the band gap blue shift varies with the dielectric layers and annealing temperature. The SiO2 capping was successfully used with an InGaAs cladding layer to cause larger band tuning effect in the InGaAs/InP MQWs than the Si3N4 capping with an InGaAs cladding layer. On the other hand, samples with the Si3N4-InP cap layer combination also show larger energy shifts than that with SiO2-InP cap layer combination.

Optical and structural characteristics of high indium content InGaN/GaN multi-quantum wells with varying GaN cap layer thickness

2015 ◽  
Vol 117 (5) ◽  
pp. 055709 ◽  
Author(s):  
J. Yang ◽  
D. G. Zhao ◽  
D. S. Jiang ◽  
P. Chen ◽  
J. J. Zhu ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Layer Thickness ◽  
Structural Characteristics ◽  
Indium Content ◽  
Cap Layer ◽  
High Indium Content

The structure of the Cincinnati arch as determined by short period Rayleigh waves

1969 ◽  
Vol 59 (1) ◽  
pp. 399-407
Author(s):  
Robert B. Herrmann
Keyword(s):  
Experimental Data ◽  
Theoretical Model ◽  
Layer Thickness ◽  
Rayleigh Waves ◽  
Layer Model ◽  
Depth Data ◽  
Short Period ◽  
Best Fitting ◽  
Good Agreement

Abstract The propagation of Rayleigh waves with periods of 0.4 to 2.0 seconds across the Cincinnati arch is investigated. The region of investigation includes southern Indiana and Ohio and northern Kentucky. The experimental data for all paths are fitted by a three-layer model of varying layer thickness but of fixed velocity in each layer. The resulting inferred structural picture is in good agreement with the known basement trends of the region. The velocities of the best fitting theoretical model agree well with velocity-depth data from a well in southern Indiana.

Effect of Thermal Annealing on the Photoluminescence Properties of a GaInNAs/GaAs Single Quantum Well

2000 ◽  
Vol 639 ◽  
Author(s):  
Laurent Grenouillet ◽  
Catherine Bru-Chevallier ◽  
Gérard Guillot ◽  
Philippe Gilet ◽  
Philippe Ballet ◽  
...  
Keyword(s):  
Quantum Well ◽  
Thermal Annealing ◽  
Low Temperatures ◽  
Blue Shift ◽  
Emission Peak ◽  
Single Quantum ◽  
Photoluminescence Properties ◽  
Single Quantum Well ◽  
Peak Energy ◽  
Strong Blue Shift

ABSTRACTWe report on the effect of thermal annealing on the photoluminescence properties of a Ga0.65In0.35N0.02As0.98/GaAs single quantum well. Thermal annealing is shown to decrease the strong nitrogen-induced localization effects observed at low temperatures and to reduce the full width at half maximum of the emission peak. It also induces a strong blue shift of the emission peak energy, which is thought not to arise from an In-Ga interdiffusion alone, as it is much larger than in a nitrogen-free reference single quantum well.

scholarly journals Effect of Yb Concentration on the Structural, Magnetic and Optoelectronic Properties of Yb Doped ZnO: First Principles Calculation

2021 ◽  
Author(s):  
Mohamed Achehboune ◽  
Mohammed Khenfouch ◽  
Issam Boukhoubza ◽  
Issam Derkaoui ◽  
Bakang Moses Mothudi ◽  
...  
Keyword(s):  
Band Gap ◽  
Conduction Band ◽  
Density Functional ◽  
Blue Shift ◽  
First Principles Calculation ◽  
Theoretical Research ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Doped Zno ◽  
Good Agreement

Abstract Density functional theory-based investigation of the electronic, magnetic, and optical characteristics in pure and ytterbium (Yb) doped ZnO has been carried out by the plane-wave pseudopotential technique with generalized gradient approximation. The calculated lattice parameters and band gap of pure ZnO are in good agreement with the experimental results. The energy band-gap increases with the increase of Yb concentration. The Fermi level moves upward into the conduction band after doping with Yb, which shows the properties of an n-type se miconductor. New defects were created in the band-gap near the conduction band attributed to the Yb-4f states. The magnetic properties of ZnO were found to be affected by Yb doping; ferromagnetic property was observed for 4.17% Yb due to spin polarization of Yb-4f electrons. The calculated optical properties imply that Yb doped causes a blue shift of the absorption peaks, significantly enhances the absorption of the visible light, and the blue shift of the reflectivity spectrum was observed. Besides, a better transmittance of approximately 88% was observed for 4.17% Yb doped ZnO system. The refractive index and the extinction coefficient were observed to decrease as the Yb dopant concentration increased. As a result, we believe that our findings will be useful in understanding the doping impact in ZnO and will motivate further theoretical research.

Characterization of Inhomogeneity in Thermal Oxide SiO2 Films on 4H-SiC Epitaxial Substrates by a Combination of Fourier Transform Infrared Spectroscopy and Cathodoluminescence Spectroscopy

2018 ◽  
Vol 924 ◽  
pp. 273-276 ◽  
Author(s):  
Masanobu Yoshikawa ◽  
Keiko Inoue ◽  
Junichiro Sameshima ◽  
Hirohumi Seki
Keyword(s):  
Fourier Transform ◽  
Oxide Layer ◽  
Layer Thickness ◽  
Phonon Mode ◽  
Fourier Transform Infrared ◽  
Blue Shift ◽  
Peak Frequency ◽  
Oxide Layer Thickness ◽  
Thermal Oxide ◽  
Ft Ir

We measured Fourier transform infrared (FT-IR) and cathodoluminescence (CL) spectra of SiO2 films with a various thickness, grown on 4H-SiC substrates. The peak frequency of the transverse optical (TO) phonon mode was blue-shifted by about 5 cm−1 as the oxide-layer thickness decreased from 50-60 nm to 10 nm. The blue shift of the TO mode is considerd to be caused by interfacial compressive stresses in the oxide-layer. On the other hand, the TO phonon mode was found to dramatically decrease as the oxide-layer thickness decreased from 10 nm to 1.7 nm. The CL measurement indicates that the intensity of the CL peaks at about 460 and 490 nm attributed to oxygen vacancy centers (OVCs) for No.2 become stronger than that for No.1. From a comparison between FT-IR and CL measurements, we concluded that the red-shift of the TO phonon with decreasing the oxide-layer thickness can mainly be attributed to an increase in inhomogeneity at the SiO2/SiC interface with decreasing oxide-layer thickness.

Vortex rings impinging on walls: axisymmetric and three-dimensional simulations

1993 ◽  
Vol 256 ◽  
pp. 615-646 ◽  
Author(s):  
Paolo Orlandi ◽  
Roberto Verzicco
Keyword(s):  
Numerical Simulations ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Vortex Rings ◽  
Compression Phase ◽  
Vortex Pairing ◽  
The Impact ◽  
Good Agreement ◽  
Three Dimensional Simulations

Accurate numerical simulations of vortex rings impinging on flat boundaries revealed the same features observed in experiments. The results for the impact with a free-slip wall compared very well with previous numerical simulations that used spectral methods, and were also in qualitative agreement with experiments. The present simulation is mainly devoted to studying the more realistic case of rings interacting with a no-slip wall, experimentally studied by Walker et al. (1987). All the Reynolds numbers studied showed a very good agreement between experiments and simulations, and, at Rev > 1000 the ejection of a new ring from the wall was seen. Axisymmetric simulations demonstrated that vortex pairing is the physical mechanism producing the ejection of the new ring. Three-dimensional simulations were also performed to investigate the effects of azimuthal instabilities. These simulations have confirmed that high-wavenumber instabilities originate in the compression phase of the secondary ring within the primary one. The large instability of the secondary ring has been explained by analysis of the rate-of-strain tensor and vorticity alignment. The differences between passive scalars and the vorticity field have been also investigated.

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