Effects of Defects in GaAs/AlGaAs Quantum Wells

1993 ◽  
Vol 325 ◽  
Author(s):  
O.L. Russo ◽  
V. Rehn ◽  
T.W. Nee ◽  
K.A. Dumas
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Wells ◽  
Point Defects ◽  
Molecular Beam ◽  
Transition Probability ◽  
Band Energy ◽  
Transmission Electron ◽  
Different Temperatures

AbstractHigh Resolution transmission electron microscopy (HRTEM) and electroreflectance (ER) were used to explain the role of point defects in the molecular beam epitaxy (MBE) grown PIN structure containing five coupled (50Å/28Å) GaAs/AlxGa1−xAs quantum wells with x = 0.25. The ER data were taken at 300K and 77K for energies from 1.4 to 2.1 eV from which sub-band energy transitions were determined. Data at 300K showed three transitions whereas four were readily resolved at 77K. HRTEM data determined the uniformity of both the wells and barriers to be within ± 2Å, which neither caused appreciable broadening nor a decrease in the transition probability. However, the data at different temperatures suggest that point defects may be responsible for the decrease in the transition probability.

Structural Characterization of Molecular Beam Epitaxy Grown GaInNAs and GaInNAsSb Quantum Wells by Transmission Electron Microscopy

2004 ◽  
Vol 817 ◽  
Author(s):  
Tihomir Gugov ◽  
Mark Wistey ◽  
Homan Yuen ◽  
Seth Bank ◽  
James S. Harris
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Wells ◽  
Phase Segregation ◽  
Dark Field ◽  
Lower Growth ◽  
Transmission Electron ◽  
Material Uniformity

AbstractIn the past decade, the quaternary GaInNAs alloy has emerged as a very promising material for lasers in the 1.2-1.6 μm range with application in telecommunication fiber-optic networks. While most of the challenges in growing high quality laser material with emission wavelength out to 1.3 μm have been successfully resolved, extending the emission beyond 1.3 μm has proven to be quite difficult. Achieving emission out to 1.5 μm requires higher In (up to 40%) and N (up to 2%) compositions. This makes the growth of this thermodynamically unstable alloy quite difficult with phase segregation occurring even at lower growth temperatures. Recently, adding small amounts of antimony has dramatically improved the quality of the material and high luminescence has been demonstrated at wavelengths beyond 1.5 μm. In this study, high-resolution transmission electron microscopy (HRTEM) was used in a novel way in conjunction with dark-field (DF) TEM to elucidate the role of antimony in improving the material quality. The results show that antimony improves the material uniformity via reduction of the local compositional fluctuations of indium.

Tem Study of Temperature Influence on The Crystalline Quality of InGaAs/Si Epilayers

1992 ◽  
Vol 263 ◽  
Author(s):  
A. Vila ◽  
A. Cornet ◽  
J.R. Morante ◽  
D.I. Westwood
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam ◽  
Temperature Influence ◽  
X Ray Diffraction ◽  
Double Crystal ◽  
X Ray ◽  
Transmission Electron ◽  
Different Temperatures

ABSTRACTA Transmission Electron Microscopy (TEM) study of In0.53Ga0.47As Molecular Beam Epitaxy films grown at different temperatures onto misoriented Si (100) substrates is presented. The evolution of the density of the different kind of defects is discussed as a function of the growth temperature in the range between 200 and 500° C. The results are compared with the characterization techniques of Double Crystal X-Ray Diffraction and Hall effect.

Role of Dopants and Impurities on Pinhole Formation; Defects Formed At Ingan/Gan And AlGaN/GaN Quantum Wells

1997 ◽  
Vol 482 ◽  
Author(s):  
Z. Liliental-Weber ◽  
S. Ruvimov ◽  
W. Swider ◽  
Y. Kim ◽  
J. Washburn ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Surface Roughness ◽  
Quantum Wells ◽  
Transmission Electron ◽  
Nanotube Defects

AbstractTransmission electron microscopy has been applied to study defects in epitaxial doped and undoped GaN layers grown by MOCVD on sapphire and SiC substrates. Samples with InGaN/GaN and AlGaN/InGaN heterostructures have also been investigated. The results of this study show that incorporation of “foreign” atoms increases formation of nano-tubes and pinholes. The highest density of these defects was formed close to the interface with sapphire where oxygen outdiffusion might be expected, or in the subsurface area in the samples where oxygen was added deliberately. Addition of In (or Al) at QW's also leads to pinhole formation. Increased In fraction or a larger number of QW's results in a greater density of pinholes and more surface roughness. Many of the “hollow” nanotube defects are terminated during growth.

Effects of Arsenic Deactivation on Arsenic-Implant Induced Enhanced Diffusion in Silicon

1995 ◽  
Vol 396 ◽  
Author(s):  
O. Dokumaci ◽  
M.E. Law ◽  
V. Krishnamoorthy ◽  
K.S. Jones
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Dose ◽  
Enhanced Diffusion ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Type V ◽  
Boron Diffusivity

AbstractThe enhanced diffusion of boron due to high dose arsenic implantation into silicon is studied as a function of arsenic dose. The behavior of both the type-V and end-of-range loops is investigated by transmission electron microscopy (TEM). The role of arsenic deactivation induced interstitials and type-V loops on enhanced diffusion is assessed. Reduction of the boron diffusivity is observed with increasing arsenic dose at three different temperatures. The possible explanations for this reduction are discussed.

Structure and Optical Properties of Si/InAs/Si Layers Grown by MBE on Si Substrate at Different Temperatures

2000 ◽  
Vol 618 ◽  
Author(s):  
N.D. Zakharov ◽  
P. Werner ◽  
U. Gösele ◽  
R. Heitz ◽  
D. Bimberg ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Transmission Electron Microscopy ◽  
Optical Properties ◽  
High Resolution ◽  
Molecular Beam ◽  
Growth Direction ◽  
Si Substrate ◽  
Transmission Electron ◽  
Different Temperatures

ABSTRACTEpitaxial Si/InAs/Si heterostructure grown on (001) Si substrate by molecular beam epitaxy (MBE) and annealed at 800°C, and 880°C were investigated by High Resolution Transmission Electron Microscopy (HRTEM). Extensive interdiffusion at 800°C leads to the formation of an InAs solid solution as well as InAs-enriched regions with extensions of ∼6nm, which exhibit two kinds of ordering. The ordering of InAs molecules occurred, respectively, in {110} planes inclined and parallel to the [001] growth direction. It is attributed to the energy gain from the reduced number of mixed Si-As and Si-In bonds. The sample grown at 800°C shows photoluminescence in the 1.3.µm region, which is tentatively attributed to the recombination of excitons localised in the ordered regions

On Future Directions in Pathology

1982 ◽  
Vol 40 ◽  
pp. 274-277
Author(s):  
Benjamin F. Trump ◽  
Irene K. Berezesky ◽  
Raymond T. Jones
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Clinical Pathology ◽  
Future Directions ◽  
Diagnostic Pathology ◽  
The Past ◽  
Transmission Electron ◽  
Organ Systems ◽  
The Many

The role of electron microscopy and associated techniques is assured in diagnostic pathology. At the present time, most of the progress has been made on tissues examined by transmission electron microscopy (TEM) and correlated with light microscopy (LM) and by cytochemistry using both plastic and paraffin-embedded materials. As mentioned elsewhere in this symposium, this has revolutionized many fields of pathology including diagnostic, anatomic and clinical pathology. It began with the kidney; however, it has now been extended to most other organ systems and to tumor diagnosis in general. The results of the past few years tend to indicate the future directions and needs of this expanding field. Now, in addition to routine EM, pathologists have access to the many newly developed methods and instruments mentioned below which should aid considerably not only in diagnostic pathology but in investigative pathology as well.

Transmission Electron Microscopy studies of texture of Cr underlayer of magnetic recording hard disk

1991 ◽  
Vol 49 ◽  
pp. 580-581
Author(s):  
L. Tang ◽  
G. Thomas ◽  
M. R. Khan ◽  
S. L. Duan
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Magnetic Recording ◽  
Magnetic Thin Films ◽  
Magnetic Films ◽  
Substrate Bias ◽  
Epitaxial Relationship ◽  
Transmission Electron

Cr thin films are often used as underlayers for Co alloy magnetic thin films, such as Co1, CoNi2, and CoNiCr3, for high density longitudinal magnetic recording. It is belived that the role of the Cr underlayer is to control the growth and texture of the Co alloy magnetic thin films, and, then, to increase the in plane coercivity of the films. Although many epitaxial relationship between the Cr underlayer and the magnetic films, such as ﹛1010﹜Co/ {110﹜Cr4, ﹛2110﹜Co/ ﹛001﹜Cr5, ﹛0002﹜Co/﹛110﹜Cr6, have been suggested and appear to be related to the Cr thickness, the texture of the Cr underlayer itself is still not understood very well. In this study, the texture of a 2000 Å thick Cr underlayer on Nip/Al substrate for thin films of (Co75Ni25)1-xTix dc-sputtered with - 200 V substrate bias is investigated by electron microscopy.

Transmission Electron Microscopy of Evaporated Perylene Thin Films

1990 ◽  
Vol 48 (2) ◽  
pp. 336-337
Author(s):  
C. Ewins ◽  
J.R. Fryer
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Molecular Electronics ◽  
High Vacuum ◽  
Amorphous Layer ◽  
Electric Heater ◽  
Transmission Electron ◽  
Polycyclic Aromatic

The preparation of thin films of organic molecules is currently receiving much attention because of the need to produce good quality thin films for molecular electronics. We have produced thin films of the polycyclic aromatic, perylene C10H12 by evaporation under high vacuum onto a potassium chloride (KCl) substrate. The role of substrate temperature in determining the morphology and crystallography of the films was then investigated by transmission electron microscopy (TEM).The substrate studied was the (001) face of a freshly cleaved crystal of KCl. The temperature of the KCl was controlled by an electric heater or a cold finger. The KCl was heated to 200°C under a vacuum of 10-6 torr and allowed to cool to the desired temperature. The perylene was then evaporated over a period of one minute from a molybdenum boat at a distance of 10cm from the KCl. The perylene thin film was then backed with an amorphous layer of carbon and floated onto copper microscope grids.

Fine structure and possible functions of the hermaphrodite duct of some pulmonate snails (Mollusca: Gastropoda)

1990 ◽  
Vol 48 (3) ◽  
pp. 68-69
Author(s):  
Alan N. Hodgson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Seminal Vesicle ◽  
Reproductive Biology ◽  
Light Microscope ◽  
Light Microscope Level ◽  
Transmission Electron ◽  
Standard Techniques

The hermaphrodite duct of pulmonate snails connects the ovotestis to the fertilization pouch. The duct is typically divided into three zones; aproximal duct which leaves the ovotestis, the middle duct (seminal vesicle) and the distal ovotestis duct. The seminal vesicle forms the major portion of the duct and is thought to store sperm prior to copulation. In addition the duct may also play a role in sperm maturation and degredation. Although the structure of the seminal vesicle has been described for a number of snails at the light microscope level there appear to be only two descriptions of the ultrastructure of this tissue. Clearly if the role of the hermaphrodite duct in the reproductive biology of pulmonatesis to be understood, knowledge of its fine structure is required.Hermaphrodite ducts, both containing and lacking sperm, of species of the terrestrial pulmonate genera Sphincterochila, Levantina, and Helix and the marine pulmonate genus Siphonaria were prepared for transmission electron microscopy by standard techniques.

Indium segregation in (111)B GaAs-InxGa1-xAs quantum wells determined by transmission electron microscopy

2001 ◽  
Vol 34 (13) ◽  
pp. 1943-1946 ◽  
Author(s):  
M Moran ◽  
H Meidia ◽  
T Fleischmann ◽  
D J Norris ◽  
G J Rees ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Wells ◽  
Transmission Electron
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