Tem and Sem Studies of Defects in Gainas and Gainasp Epitaxial-Layer Device-Type Structures

1980 ◽  
Vol 2 ◽  
Author(s):  
M.M. Al-Jassim ◽  
M. Hockly ◽  
G.R. Booker
Keyword(s):  
Structural Information ◽  
Three Dimensional ◽  
Luminescent Properties ◽  
Vapour Phase ◽  
Structural Defects ◽  
Vapour Phase Epitaxy ◽  
Voltage Electron ◽  
Device Type ◽  
Dimensional Distribution ◽  
Sem Studies

ABSTRACTTEM and SEM studies have been carried out on a series of GaAs/GaInAs, InP/GaInAs and InP/GaInAsP device-type structures grown either by vapour phase epitaxy (VPE) or liquid phase epitaxy (LPE). By using the TEM high voltage electron microscope operating at 1000kV, a determination was made of the nature, origin and three-dimensional distribution of structural defects in these specimens (mainly dislocations and stacking faults). SEM EBIC and CL examinations were also performed to study the electrical and luminescent properties of these layers. The ultimate aim is to correlate structural information with electrical and luminescent properties, and with device performance.

Fabrication of Light-Emitting Diodes with Dislocation-Related Luminescence by Annealing of Electron-Irradiated Silicon

2013 ◽  
Vol 205-206 ◽  
pp. 305-310 ◽  
Author(s):  
N.A. Sobolev ◽  
P.N. Aruev ◽  
Anton E. Kalyadin ◽  
Elena I. Shek ◽  
V.V. Zabrodskiy ◽  
...  
Keyword(s):  
Room Temperature ◽  
Light Emitting Diodes ◽  
Luminescent Properties ◽  
Vapour Phase ◽  
Structural Defects ◽  
Electroluminescence Spectrum ◽  
Vapour Phase Epitaxy ◽  
Light Emitting ◽  
Annealing Conditions ◽  
Dislocation Related Luminescence

Structural defects induced by electron irradiation of n-Cz-Si wafers were identified. The influence of the annealing conditions in a chlorine-containing atmosphere on the structural and luminescent properties of the samples was examined and the optimal annealing conditions were found. Light-emitting diodes based on electron-irradiated and high-temperature-annealed wafers were fabricated by a vapour-phase epitaxy technique and their luminescence properties were studied. A high-intensity dislocation-related D1 line was observed at 1.6 μm in the room-temperature electroluminescence spectrum.

Ion Scattering Studies of Defects In Gan Thin Films on C-Oriented Sapphire

1998 ◽  
Vol 512 ◽  
Author(s):  
B. Holländer ◽  
S. Mantl ◽  
M. Mayer ◽  
C. Kirchner ◽  
A. Pelzmann ◽  
...  
Keyword(s):  
Lattice Mismatch ◽  
Vapour Phase ◽  
Structural Defects ◽  
Ion Scattering ◽  
Vapour Phase Epitaxy ◽  
Screw Dislocations ◽  
Ion Channeling ◽  
Thermal Expansion Coefficients ◽  
Organic Vapour ◽  
Edge Dislocations

ABSTRACTEpitaxial GaN films grown by metal organic vapour phase epitaxy (MOVPE) or gas source molecular beam epitaxy (GSMBE) have opened up new applications in short wavelength photonic devices as well as high-power and high-temperature devices. The large lattice mismatch of 14% between GaN and sapphire, which is frequently used as the substrate, and the different thermal expansion coefficients generally lead to high densities of structural defects. We investigate the defect structure of MOVPE- and GSMBE-grown GaN layers on sapphire by Rutherford backscattering and ion channeling measurements. Channeling along the c-axis revealed χmin-values as low as 1.2% even in samples with dislocation densities in the order of 109 cm−2. Channeling measurements along different crystal planes were performed in order to improve the sensitivity to dechanneling by crystalline defects. Angular yield scans around the c-axis indicate clearly the hexagonal symmetry of the GaN lattice. Dechanneling results were combined with transmission electron microscopy investigations (TEM). The results suggest that the dechanneling-cross-section of edge dislocations is about 4 times larger than the dechannelingcross-section of screw dislocations. screw dislocations.

scholarly journals A tool for automatic recognition of [110] tilt grain boundaries in zincblende-type crystals

2017 ◽  
Vol 50 (5) ◽  
pp. 1299-1306 ◽  
Author(s):  
Roksolana Kozak ◽  
Fiodar Kurdzesau ◽  
Ivan Prieto ◽  
Oliver Skibitzki ◽  
Thomas Schroeder ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Three Dimensional ◽  
Vapour Phase ◽  
Dark Field ◽  
Vapour Phase Epitaxy ◽  
Unit Model ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Common Plane ◽  
Organic Vapour

The local atomic structure of [110] tilt grain boundaries (GBs) formed in ∼100 nm-sized GaAs nanocrystals, which crystallize in the non-centrosymmetric zincblende-type structure with face-centred cubic lattice symmetry, was imaged and analysed by means of high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The nanocrystals were grown by metal–organic vapour phase epitaxy on top of (001) Si nanotips embedded in an oxide matrix. This paper introduces an automatic analysis method and corresponding processing tool for the identification of the GBs. The method comprises (i) extraction of crystallographic parameters,i.e.misorientation angles and transformation matrices for the different crystal parts (grains/twins) observed by HAADF-STEM, and (ii) determination of their common plane(s) by modelling all possible intersections of the corresponding three-dimensional reciprocal lattices. The structural unit model is also used to characterize the GB structures and to validate the data obtained by the developed algorithm.

Coherent diffraction imaging: consistency of the assembled three-dimensional distribution

2016 ◽  
Vol 72 (4) ◽  
pp. 459-464 ◽  
Author(s):  
Miklós Tegze ◽  
Gábor Bortel
Keyword(s):  
Structural Information ◽  
Three Dimensional ◽  
Atomic Scale ◽  
Short Pulses ◽  
X Ray ◽  
Coherent Diffraction Imaging ◽  
Imaging Experiment ◽  
Dimensional Distribution ◽  
Diffraction Imaging ◽  
Diffraction Patterns

The short pulses of X-ray free-electron lasers can produce diffraction patterns with structural information before radiation damage destroys the particle. From the recorded diffraction patterns the structure of particles or molecules can be determined on the nano- or even atomic scale. In a coherent diffraction imaging experiment thousands of diffraction patterns of identical particles are recorded and assembled into a three-dimensional distribution which is subsequently used to solve the structure of the particle. It is essential to know, but not always obvious, that the assembled three-dimensional reciprocal-space intensity distribution is really consistent with the measured diffraction patterns. This paper shows that, with the use of correlation maps and a single parameter calculated from them, the consistency of the three-dimensional distribution can be reliably validated.

scholarly journals Growth Uniformity in Selective Area Epitaxy of AlGaN/GaN Heterostructures for the Application in Semiconductor Devices

Electronics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 2129
Author(s):  
Michał Stępniak ◽  
Mateusz Wośko ◽  
Joanna Prażmowska-Czajka ◽  
Andrzej Stafiniak ◽  
Dariusz Przybylski ◽  
...  
Keyword(s):  
Diffusion Length ◽  
Semiconductor Devices ◽  
Three Dimensional ◽  
Theoretical Models ◽  
Vapour Phase ◽  
High Electron ◽  
Device Structure ◽  
Vapour Phase Epitaxy ◽  
Window Width ◽  
Selective Area

The design of modern semiconductor devices often requires the fabrication of three-dimensional (3D) structures to integrate microelectronic components with photonic, micromechanical, or sensor systems within one semiconductor substrate. It is a technologically challenging task, as a strictly defined profile of the device structure is obligatory. This can be achieved either by chemical etching or selective deposition on a masked substrate. In this paper, the growth uniformity of AlGaN/GaN heterostructures during selective-area metalorganic vapour-phase epitaxy (SA-MOVPE) was studied. Such structures are typically used in order to fabricate high-electron-mobility transistors (HEMT). The semiconductor material was deposited through 200 μm long stripe-shaped open windows in a SiO2 mask on GaN/sapphire templates. The window width was varied from 5 μm to 160 μm, whereas mask width separating particular windows varied from 5 μm to 40 μm. The experiment was repeated for three samples differing in GaN layer thickness: 150 nm, 250 nm, and 500 nm. Based on theoretical models of the selective growth, a sufficiently uniform thickness of epitaxially grown AlGaN/GaN heterostructure has been achieved by selecting the window half-width that is smaller than the diffusion length of the precursor molecules. A Ga diffusion length of 15 μm was experimentally extracted by measuring the epitaxial material agglomeration in windows in the dielectric mask. Measurements were conducted while using optical profilometry.

Approaches for High Resolution Cryo-Electron Tomography of Biological Specimens

1997 ◽  
Vol 3 (S2) ◽  
pp. 1111-1112
Author(s):  
D.A. Agard ◽  
M.B. Braunfeld ◽  
Hans Chen ◽  
Rebecca McQuitty ◽  
John Sedat
Keyword(s):  
Data Collection ◽  
Structural Information ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Electron Microscopic ◽  
Subcellular Organelles ◽  
Voltage Electron ◽  
Cell Components ◽  
Electron Microscopes ◽  
Biological Complexes

Electron tomography is a powerful tool for elucidating the three-dimensional architecture of large biological complexes and subcellular organelles. Use of intermediate voltage electron microscopes extended the technique by providing the means to examine very large and non-symmetrical subcellular organelles, at resolutions beyond what would be possible using light microscopy. Recent studies using electron tomography on a variety cellular organelles and assemblies such as centrosomes (Moritz et al.,1995a,b), kinetochores (McEwen, 1993) and chromatin (Woodcock, 1994), have clearly demonstrated the power of this method for obtaining 3D structural information on non-symmetric cell components. When combined with biochemical and molecular observations, these 3D reconstructions have provided significant new insights into biological function.Although the information that tomography provides is unique, its use as a general tool in the biological community has been limited due to the complexities involved in data collection and processing.We are simultaneously trying to make this approach accessible through automation as well as trying to extend the resolution and accuracy of the reconstructions. Significant, has been the use of low-dose cryo-electron microscopic automated data collection methods.

scholarly journals Reduction of surface roughness by modification of step-bunched aluminum nitride layers towards step-flow morphology

2020 ◽  
Vol 59 (4) ◽  
Author(s):  
Nadine Tillner ◽  
Christian Brandl ◽  
Marc P. Hoffmann ◽  
Richard Moser ◽  
Andreas Waag ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Aluminum Nitride ◽  
Three Dimensional ◽  
Spectral Width ◽  
Vapour Phase ◽  
Layer Growth ◽  
Vapour Phase Epitaxy ◽  
Light Emitting ◽  
Nitride Layers ◽  
Peak Emission

Conventional aluminum nitride (AlN) template fabrication techniques, like hydride vapour phase epitaxy or AlN growth on patterned sapphire substrates, usually lead to step-bunched template surfaces. The resulting macrosteps cause emission broadening or even multiple-peak characteristics of ultraviolet light-emitting diodes (UV LEDs) fabricated on such AlN templates. In order to reduce these macrosteps and to provide a smoother surface, even without the need of a thick AlN deposition, a two-layer growth procedure is reported here. A three-dimensional (3D) – twodimensional (2D) sequential growth initiates a significant modification of the previous AlN surface morphology and simultaneously limits the evolving tensile strain. A primarily step-bunched surface with a surface roughness root mean square of 1.8 nm is successfully reduced by the two-layer growth procedure down to 0.8 nm, without any film cracking. This distinct roughness reduction of more than 50% is achieved within an AlN thickness of only 1.3 µm. With a smoother surface, the electroluminescence characteristic of a UV LED structure is substantially improved. Instead of a double-peak emission, typical for LEDs grown on step-bunched templates, a single-peak emission and lower spectral width were achieved, indicating the high potential of the suggested two-layer technique for improving performance.

Three-Dimensional Visualization of the T-System of Frog Muscle Using High Voltage Electron Microscopy and a Lanthanum Stain

1977 ◽  
Vol 35 ◽  
pp. 570-571 ◽  
Author(s):  
Lee D. Peachey ◽  
Clara Franzini-Armstrong
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Three Dimensional ◽  
Biological Tissues ◽  
High Voltage Electron Microscopy ◽  
Transverse Tubular System ◽  
Peroxidase Reaction ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
T System

The effective study of biological tissues in thick slices of embedded material by high voltage electron microscopy (HVEM) requires highly selective staining of those structures to be visualized so that they are not hidden or obscured by other structures in the image. A tilt pair of micrographs with subsequent stereoscopic viewing can be an important aid in three-dimensional visualization of these images, once an appropriate stain has been found. The peroxidase reaction has been used for this purpose in visualizing the T-system (transverse tubular system) of frog skeletal muscle by HVEM (1). We have found infiltration with lanthanum hydroxide to be particularly useful for three-dimensional visualization of certain aspects of the structure of the T- system in skeletal muscles of the frog. Specifically, lanthanum more completely fills the lumen of the tubules and is denser than the peroxidase reaction product.

A New 1000kv Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 100-101
Author(s):  
J.L. Williams ◽  
K. Heathcote ◽  
E.J. Greer
Keyword(s):  
Electron Microscope ◽  
Direct Observation ◽  
High Voltage ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Specimen Thickness ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
Dynamic Experiments ◽  
Conventional Instrument

High Voltage Electron Microscope already offers exciting experimental possibilities to Biologists and Materials Scientists because the increased specimen thickness allows direct observation of three dimensional structure and dynamic experiments on effectively bulk specimens. This microscope is designed to give maximum accessibility and space in the specimen region for the special stages which are required. At the same time it provides an ease of operation similar to a conventional instrument.

High-voltage electron microscopy of maxillary gland of spirochete-infected brine shrimp: lesion of efferent tubule

1988 ◽  
Vol 46 ◽  
pp. 362-363
Author(s):  
G. E. Tyson ◽  
M. J. Song
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Brine Shrimp ◽  
Natural Populations ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Infected Adult

Natural populations of the brine shrimp, Artemia, may possess spirochete- infected animals in low numbers. The ultrastructure of Artemia's spirochete has been described by conventional transmission electron microscopy. In infected shrimp, spirochetal cells were abundant in the blood and also occurred intra- and extracellularly in the three organs examined, i.e. the maxillary gland (segmental excretory organ), the integument, and certain muscles The efferent-tubule region of the maxillary gland possessed a distinctive lesion comprised of a group of spirochetes, together with numerous small vesicles, situated in a cave-like indentation of the base of the tubule epithelium. in some instances the basal lamina at a lesion site was clearly discontinuous. High-voltage electron microscopy has now been used to study lesions of the efferent tubule, with the aim of understanding better their three-dimensional structure.Tissue from one maxillary gland of an infected, adult, female brine shrimp was used for HVEM study.

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