Strain relaxation and band-gap tunability in ternaryInxGa1−xNnanowires

2008 ◽  
Vol 78 (19) ◽  
Author(s):  
H. J. Xiang ◽  
Su-Huai Wei ◽  
Juarez L. F. Da Silva ◽  
Jingbo Li
Keyword(s):  
Band Gap ◽  
Strain Relaxation

Schottky Diodes on Si1-x-yGexCy Alloys.

1995 ◽  
Vol 379 ◽  
Author(s):  
M. Mamnor ◽  
C. Guedj ◽  
P. Boucaud ◽  
F. Meyer ◽  
D. Bouchier ◽  
...  
Keyword(s):  
Band Gap ◽  
Barrier Height ◽  
Strain Relaxation ◽  
Schottky Diodes ◽  
Chemical Vapor ◽  
Schottky Barriers ◽  
X Ray Diffraction ◽  
Germanium Content ◽  
Hole Effective Mass ◽  
P Type

ABSTRACTWe have recently investigated the properties of W/Si1-xGex films prepared by rapid thermal chemical vapor deposition (RTCVD). The barrier height on p-type, ΦBp, varies as the band gap with the germanium content for totally relaxed films, and increases with strain relaxation, while that on n-type remains rather constant. These results suggest that the Fermi level is pinned relative to the conduction band at the interface of the binary alloy and that the measurement of Schottky barriers is a suitable tool to follow band gap variations. In this work, the effects of carbon incorporation on Schottky barriers have been investigated. The study has been performed on Si1-x-yGexCy films (0≤y≤1.35% with x=10%). The strain retained in the films was determined by X-ray diffraction. Infrared absorption measurements have shown that the carbon is incorporated on substitutional sites. The electrical results indicate the same trends than those observed on the binary alloys, the barrier height on n-type remains rather constant while the barrier height on p-type varies. Adding C leads to an increase of ΦBp, but this increase is too large to be explained in terms of variation of the band gap. The influence of other parameters, such as the doping level and the hole effective mass is discussed.

Misfit strain, relaxation, and band‐gap shift in GaxIn1−xP/InP epitaxial layers

1994 ◽  
Vol 75 (6) ◽  
pp. 3024-3029 ◽  
Author(s):  
A. Bensaada ◽  
A. Chennouf ◽  
R. W. Cochrane ◽  
J. T. Graham ◽  
R. Leonelli ◽  
...  
Keyword(s):  
Band Gap ◽  
Strain Relaxation ◽  
Misfit Strain ◽  
Epitaxial Layers

scholarly journals Minimizing Defect States in Lead Halide Perovskite Solar Cell Materials

2020 ◽  
Author(s):  
René M. Williams ◽  
Rosa Brakkee
Keyword(s):  
Band Gap ◽  
Chemical Bonding ◽  
Lattice Strain ◽  
Strain Relaxation ◽  
Vacancy Formation ◽  
Rational Approach ◽  
Computational Studies ◽  
Nonradiative Recombination ◽  
Defect States ◽  
Halide Perovskite

In order to reach the theoretical efficiency limits of lead-based metal halide perovskite solar cells, the voltage should be enhanced because it suffers from nonradiative recombination. Perovskite materials contain intrinsic defects that can act as Shockley-Read-Hall recombination centers. Several experimental and computational studies have characterized such defect states within the band gap. We give a systematic overview of compositional engineering by distinguishing the different defect reducing mechanisms. Doping effects are divided into influences on: (1) Crystallization; (2) Lattice properties. Incorporation of dopant influences the lattice properties by: (a) Lattice strain relaxation; (b) Chemical bonding enhancement; (c) Band gap tuning. The intrinsic lattice strain in undoped perovskite was shown to induce vacancy formation. The incorporation of smaller ions, such as Cl, F and Cd, increases the energy for vacancy formation. Zn doping is reported to induce strain relaxation but also to enhance the chemical bonding. The combination of computational studies using (DFT) calculations quantifying and qualifying the defect reducing propensities of different dopants with experimental studies is essential for deeper understanding and unraveling insights, such as the dynamics of iodine vacancies and the photochemistry of the iodine interstitials, and can eventually lead to a more rational approach in the search for optimal photovoltaic materials.

scholarly journals Minimizing Defect States in Lead Halide Perovskite Solar Cell Materials

2020 ◽  
Vol 10 (9) ◽  
pp. 3061 ◽  
Author(s):  
Rosa Brakkee ◽  
René M. Williams
Keyword(s):  
Band Gap ◽  
Chemical Bonding ◽  
Lattice Strain ◽  
Strain Relaxation ◽  
Perovskite Solar Cells ◽  
Vacancy Formation ◽  
Rational Approach ◽  
Computational Studies ◽  
Defect States ◽  
Halide Perovskite

In order to reach the theoretical efficiency limits of lead-based metal halide perovskite solar cells, the voltage should be enhanced because it suffers from non-radiative recombination. Perovskite materials contain intrinsic defects that can act as Shockley–Read–Hall recombination centers. Several experimental and computational studies have characterized such defect states within the band gap. We give a systematic overview of compositional engineering by distinguishing the different defect-reducing mechanisms. Doping effects are divided into influences on: (1) crystallization; (2) lattice properties. Incorporation of dopant influences the lattice properties by: (a) lattice strain relaxation; (b) chemical bonding enhancement; (c) band gap tuning. The intrinsic lattice strain in undoped perovskite was shown to induce vacancy formation. The incorporation of smaller ions, such as Cl, F and Cd, increases the energy for vacancy formation. Zn doping is reported to induce strain relaxation but also to enhance the chemical bonding. The combination of computational studies using (DFT) calculations quantifying and qualifying the defect-reducing propensities of different dopants with experimental studies is essential for a deeper understanding and unraveling insights, such as the dynamics of iodine vacancies and the photochemistry of the iodine interstitials, and can eventually lead to a more rational approach in the search for optimal photovoltaic materials.

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.

TEM study of phosphorus-implanted pseudomorphic Si0.88Ge0.12 on Si(100)

1995 ◽  
Vol 53 ◽  
pp. 468-469
Author(s):  
N. David Theodore ◽  
Donald Y.C Lie ◽  
J. H. Song ◽  
Peter Crozier
Keyword(s):  
Integrated Circuits ◽  
Heterojunction Bipolar Transistors ◽  
Integrated Circuit ◽  
High Speed ◽  
Room Temperature ◽  
Strain Relaxation ◽  
Bipolar Transistors ◽  
Sige Hbt ◽  
Integrated Circuit Manufacturing ◽  
Microstructural Behavior

SiGe is being extensively investigated for use in heterojunction bipolar-transistors (HBT) and high-speed integrated circuits. The material offers adjustable bandgaps, improved carrier mobilities over Si homostructures, and compatibility with Si-based integrated-circuit manufacturing. SiGe HBT performance can be improved by increasing the base-doping or by widening the base link-region by ion implantation. A problem that arises however is that implantation can enhance strain-relaxation of SiGe/Si.Furthermore, once misfit or threading dislocations result, the defects can give rise to recombination-generation in depletion regions of semiconductor devices. It is of relevance therefore to study the damage and anneal behavior of implanted SiGe layers. The present study investigates the microstructural behavior of phosphorus implanted pseudomorphic metastable Si0.88Ge0.12 films on silicon, exposed to various anneals.Metastable pseudomorphic Si0.88Ge0.12 films were grown ~265 nm thick on a silicon wafer by molecular-beam epitaxy. Pieces of this wafer were then implanted at room temperature with 100 keV phosphorus ions to a dose of 1.5×1015 cm-2.

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.

DISORDER INDUCED DENSITY OF STATES WITHIN THE BAND GAP

1981 ◽  
Vol 42 (C4) ◽  
pp. C4-59-C4-62
Author(s):  
H. Leschke ◽  
B. Kramer
Keyword(s):  
Band Gap ◽  
Density Of States
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