Analysis of confinement potential fluctuation and band-gap renormalization effects on excitonic transition in GaAs/AlGaAs multiquantum wells grown on (100) and (311)A GaAs surfaces

2012 ◽  
Vol 407 (12) ◽  
pp. 2131-2135 ◽  
Author(s):  
S.A. Lourenço ◽  
M.D. Teodoro ◽  
P.P. González-Borrero ◽  
I.F.L. Dias ◽  
J.L. Duarte ◽  
...  
Keyword(s):  
Band Gap ◽  
Potential Fluctuation ◽  
Confinement Potential ◽  
Excitonic Transition

Band-gap narrowing and potential fluctuation in Si-doped GaN

1999 ◽  
Vol 74 (1) ◽  
pp. 102-104 ◽  
Author(s):  
In-Hwan Lee ◽  
J. J. Lee ◽  
P. Kung ◽  
F. J. Sanchez ◽  
M. Razeghi
Keyword(s):  
Band Gap ◽  
Potential Fluctuation ◽  
Si Doped ◽  
Band Gap Narrowing

scholarly journals Optoelectronic Properties of Atomically Thin MoxW(1-x)S2 Nanoflakes Probed by Spatially-Resolved Monochromated EELS

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3218
Author(s):  
Mario Pelaez-Fernandez ◽  
Yung-Chang Lin ◽  
Kazu Suenaga ◽  
Raul Arenal
Keyword(s):  
Band Gap ◽  
2D Materials ◽  
High Energy ◽  
Two Dimensional ◽  
Low Loss ◽  
Huge Amount ◽  
Band Gap Engineering ◽  
Spatially Resolved ◽  
Excitonic Transition ◽  
Electron Energy Loss

Band gap engineering of atomically thin two-dimensional (2D) materials has attracted a huge amount of interest as a key aspect to the application of these materials in nanooptoelectronics and nanophotonics. Low-loss electron energy loss spectroscopy has been employed to perform a direct measurement of the band gap in atomically thin MoxW(1−x)S2 nanoflakes. The results show a bowing effect with the alloying degree, which fits previous studies focused on excitonic transitions. Additional properties regarding the Van Hove singularities in the density of states of these materials, as well as high energy excitonic transition, have been analysed as well.

scholarly journals PbI2 Single Crystal Growth and Its Optical Property Study

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 589 ◽  
Author(s):  
Lin ◽  
Guo ◽  
Dai ◽  
Lin ◽  
Hsu
Keyword(s):  
Band Gap ◽  
Chemical Vapor ◽  
Band Gap Energy ◽  
Chemical Vapor Transport ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gap Energy ◽  
Photoelectric Properties ◽  
Metal Semiconductor Metal ◽  
Excitonic Transition

In this work, we used the chemical vapor transport (CVT) method to grow PbI2 crystals using iodine as a self-transporting agent. The crystals’ structure, composition, and uniformity were confirmed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) measurements. We investigated the band gap energy using absorption spectroscopy measurements. Furthermore, we explored the temperature dependence of the band gap energy, which shifts from 2.346 eV at 300 K to 2.487 eV at 20 K, and extracted the temperature coefficients. A prototype photodetector with a lateral metal–semiconductor–metal (MSM) configuration was fabricated to evaluate its photoelectric properties using a photoconductivity spectrum (PC) and persistent photoconductivity (PPC) experiments. The resonance-like PC peak indicates the excitonic transition in absorption. The photoresponse ILight/IDark-1 is up to 200%.

Competition between confinement potential fluctuations and band-gap renormalization effects inIn0.53Ga0.47As/In0.525Ga0.235Al0.25Assingle and double quantum wells

2008 ◽  
Vol 77 (16) ◽  
Author(s):  
José Leonil Duarte ◽  
Luiz Carlos Poças ◽  
Edson Laureto ◽  
Ivan Frederico Lupiano Dias ◽  
Élder Mantovani Lopes ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Band Gap ◽  
Double Quantum ◽  
Potential Fluctuations ◽  
Confinement Potential

NUMERICAL STUDIES OF BAND GAP RENORMALIZATION IN V-GROOVED NANO-WIRES

2006 ◽  
Vol 20 (15) ◽  
pp. 911-922
Author(s):  
K. NOZARI ◽  
M. MADADI ◽  
N. NARIMANI
Keyword(s):  
Band Gap ◽  
Quantum Wire ◽  
Electron Hole ◽  
Confinement Potential ◽  
Exchange Correlation ◽  
Numerical Studies ◽  
Electron Hole Plasma ◽  
Screened Coulomb Potential ◽  
Nano Wires ◽  
Dynamical Screening

By considering a suitable confinement potential, we calculate the exchange-correlation induced band gap renormalization (BGR) in a V-grooved quantum wire as a function of the electron-hole plasma density and quantum wire width. The leading-order GW dynamical screening approximation is used in the calculation by treating the electron-electron Coulomb interaction and electron-optical phonon interaction. A numerical scheme has been proposed, and the screened Coulomb potential, density of states (profile of charge distribution) and the value of the renormalized gap energy are calculated. We will show that the carrier concentration, the screened confinement potential and the relative band gap renormalization are functions of the ratio of the well width in the x and y directions.

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

Structural properties of GaAs/InGaAs/GaAs (001) and InGaAs/GaAs (001) heterostructures and correlation with electronic properties

1990 ◽  
Vol 48 (4) ◽  
pp. 602-603
Author(s):  
J.M. Bonar ◽  
R. Hull ◽  
R. Malik ◽  
R. Ryan ◽  
J.F. Walker
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Gaas Substrate ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Band Offset ◽  
Misfit Dislocations ◽  
Gaas Substrates ◽  
Gaas Structure ◽  
Low X

In this study we have examined a series of strained heteropeitaxial GaAs/InGaAs/GaAs and InGaAs/GaAs structures, both on (001) GaAs substrates. These heterostructures are potentially very interesting from a device standpoint because of improved band gap properties (InAs has a much smaller band gap than GaAs so there is a large band offset at the InGaAs/GaAs interface), and because of the much higher mobility of InAs. However, there is a 7.2% lattice mismatch between InAs and GaAs, so an InxGa1-xAs layer in a GaAs structure with even relatively low x will have a large amount of strain, and misfit dislocations are expected to form above some critical thickness. We attempt here to correlate the effect of misfit dislocations on the electronic properties of this material.The samples we examined consisted of 200Å InxGa1-xAs layered in a hetero-junction bipolar transistor (HBT) structure (InxGa1-xAs on top of a (001) GaAs buffer, followed by more GaAs, then a layer of AlGaAs and a GaAs cap), and a series consisting of a 200Å layer of InxGa1-xAs on a (001) GaAs substrate.

Modification of optical properties of PC-PBT/Cr2O3 and PC-PBT/CdS nanocomposites by gamma irradiation

2020 ◽  
Vol 92 (2) ◽  
pp. 20402
Author(s):  
Kaoutar Benthami ◽  
Mai ME. Barakat ◽  
Samir A. Nouh
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Color Difference ◽  
Band Gap Energy ◽  
Polybutylene Terephthalate ◽  
Γ Irradiation ◽  
Gap Energy ◽  
Vis Spectroscopy ◽  
Oxygen Atoms

Nanocomposite (NCP) films of polycarbonate-polybutylene terephthalate (PC-PBT) blend as a host material to Cr2O3 and CdS nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Samples from the PC-PBT/Cr2O3 and PC-PBT/CdS NCPs were irradiated using different doses (20–110 kGy) of γ radiation. The induced modifications in the optical properties of the γ irradiated NCPs have been studied as a function of γ dose using UV Vis spectroscopy and CIE color difference method. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the NCP films and to identify the types of electronic transition. The value of optical band gap energy of PC-PBT/Cr2O3 NCP was reduced from 3.23 to 3.06 upon γ irradiation up to 110 kGy, while it decreased from 4.26 to 4.14 eV for PC-PBT/CdS NCP, indicating the growth of disordered phase in both NCPs. This was accompanied by a rise in the refractive index for both the PC-PBT/Cr2O3 and PC-PBT/CdS NCP films, leading to an enhancement in their isotropic nature. The Cr2O3 NPs were found to be more effective in changing the band gap energy and refractive index due to the presence of excess oxygen atoms that help with the oxygen atoms of the carbonyl group in increasing the chance of covalent bonds formation between the NPs and the PC-PBT blend. Moreover, the color intensity, ΔE has been computed; results show that both the two synthesized NCPs have a response to color alteration by γ irradiation, but the PC-PBT/Cr2O3 has a more response since the values of ΔE achieved a significant color difference >5 which is an acceptable match in commercial reproduction on printing presses. According to the resulting enhancement in the optical characteristics of the developed NCPs, they can be a suitable candidate as activate materials in optoelectronic devices, or shielding sheets for solar cells.

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