Dissociation of Misfit Dislocations in GeSi/{111}Si Interfaces

1993 ◽  
Vol 319 ◽  
Author(s):  
Frank Ernst
Keyword(s):  
Lattice Mismatch ◽  
Stacking Faults ◽  
Chemical Vapor ◽  
Interfacial Area ◽  
Dark Field ◽  
Dislocation Network ◽  
Misfit Dislocations ◽  
Si Substrates ◽  
Weak Beam ◽  
Transmission Electron

AbstractThe accommodation of lattice mismatch is studied in Ge0.15Si0.85 layers grown epitaxially on {111}-oriented Si substrates by chemical vapor deposition (CVD) at 1100°C. Weak beam dark field microscopy reveals a regular misfit dislocation network, which resembles the honeycomb network of edge-type dislocations anticipated by the O-lattice theory. In contrast to the latter, however, the real network exhibits extended nodes where the misfit dislocations dissociate into misfit partial dislocations. Between the partials, high resolution transmission electron microscopy (HRTEM) reveals intrinsic and extrinsic stacking faults. Owing to the presence of these stacking faults, three different atomistic structures of the GeSi/Si interface coexist and compete for the interfacial area according to their energy. The observed configuration is shown to minimize the total energy of the interface.

TEM evaluation of graded SixGe1-x heterolayers

1991 ◽  
Vol 49 ◽  
pp. 894-895
Author(s):  
N. David Theodore ◽  
Mamoru Tomozane ◽  
Ming Liaw
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
Gas Flow ◽  
Field Effect Transistors ◽  
Chemical Vapor ◽  
Dark Field ◽  
Bipolar Transistors ◽  
Structural Quality ◽  
Weak Beam ◽  
Transmission Electron ◽  
And Behavior

There is extensive interest in SiGe for use in heterojunction bipolar transistors. SiGe/Si superlattices are also of interest because of their potential for use in infrared detectors and field-effect transistors. The processing required for these materials is quite compatible with existing silicon technology. However, before SiGe can be used extensively for devices, there is a need to understand and then control the origin and behavior of defects in the materials. The present study was aimed at investigating the structural quality of, and the behavior of defects in, graded SiGe layers grown by chemical vapor deposition (CVD).The structures investigated in this study consisted of Si1-xGex[x=0.16]/Si1-xGex[x= 0.14, 0.13, 0.12, 0.10, 0.09, 0.07, 0.05, 0.04, 0.005, 0]/epi-Si/substrate heterolayers grown by CVD. The Si1-xGex layers were isochronally grown [t = 0.4 minutes per layer], with gas-flow rates being adjusted to control composition. Cross-section TEM specimens were prepared in the 110 geometry. These were then analyzed using two-beam bright-field, dark-field and weak-beam images. A JEOL JEM 200CX transmission electron microscope was used, operating at 200 kV.

A Weak-Beam Dark-Field Study of Stacking Faults in a Co-Cr-Mo-C Alloy

1976 ◽  
Vol 34 ◽  
pp. 378-379
Author(s):  
Ernest L. Hall
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Field Study ◽  
Previous Investigation ◽  
Stacking Faults ◽  
Aging Treatment ◽  
Dark Field ◽  
Bright Field ◽  
Weak Beam ◽  
Transmission Electron

In a previous investigation (1) of the mechanisms of strengthening in a Co-28 wt% Cr-6 wt% Mo-0.29 wt% C alloy (H.S. 21), it was observed that the fee regions of this alloy were generally heavily faulted, and the density of stacking faults was seen to be dependent upon the time and temperature of the aging treatment after solutionizing. In the present study, weak-beam darkfield transmission electron microscopy was used to examine the interaction of stacking faults on intersecting {111} planes. The alloy was solutionized at 1230°C for 4 hours, quenched in water, and aged at 650°C for 8 hours in order to produce a suitable density of faults. Figure 1 shows a bright-field (BF), weak-beam dark-field (WB DF) pair of micrographs illustrating both the successful and unsuccessful intersection of faults which exist in different ﹛111﹜ planes.

Surface Morphology of SiGe Epitaxial Layers Grown on Uniquely Oriented Si Substrates

2000 ◽  
Vol 648 ◽  
Author(s):  
Morgan E. Ware ◽  
Robert J. Nemanich
Keyword(s):  
Surface Morphology ◽  
Lattice Mismatch ◽  
Morphological Structure ◽  
Epitaxial Layers ◽  
Misfit Dislocations ◽  
Force Microscopy ◽  
Si Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Relationship Of

AbstractThe 4% lattice mismatch between Si and Ge creates strain in epitaxial layers of SiGe alloys on Si, and this strain can manifest itself in the morphological structure of the surface of the epitaxial layer. This study explores the relationship of the evolution of the surface morphology of SiGe layers grown on a range of Si surface orientations. We have grown thin, strained and thick, relaxed layers of Si0.7Ge0.3 by solid source molecular beam epitaxy on substrates with surface normals rotated from [001] towards [111] by angles of θ = (0, 2, 4, 10, 22) degrees. The surface morphology was investigated by atomic force microscopy, which showed considerable ordering of surface features on relaxed samples. These features evolve from hut-like structures at 0 degrees to large mesa-like structures separated by pits and crevices at 22 degrees. The organization of these features is also shown to vary with the substrate orientation. Each surface has characteristic directions along which features are aligned, and these directions vary continuously with the angle of rotation of the substrate. Transmission electron microscopy confirmed that misfit dislocations had formed along those same directions. The state of relaxation of each layer is quantified by Raman spectroscopy in order to make a direct correlation between residual strain and surface morphology.

Generation and Suppression of Stacking Faults in Gap Layers Grown on Si(100) Substrates by Molecular Beam Epitaxy and Migration Enhanced Epitaxy

1996 ◽  
Vol 441 ◽  
Author(s):  
Y. Takagi ◽  
H. Yonezu ◽  
K. Samonji ◽  
T. Tsuji ◽  
N. Ohshima
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Stacking Faults ◽  
Misfit Dislocations ◽  
Generation Process ◽  
Si Substrates ◽  
Transmission Electron ◽  
Migration Enhanced Epitaxy ◽  
Regular Network ◽  
And Migration

AbstractWe have investigated the generation process of crystalline defects in GaP layers grown on Si substrates (GaP/Si) by molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). Transmission electron microscopy observations revealed that a regular network of misfit dislocations was generated in GaP/Si by MEE. On the other hand, threading dislocations as well as interfacial misfit dislocations were observed in GaP/Si by MBE. Moreover, stacking faults were generated in high density at the hetero-interface of GaP/Si by MBE. The density of stacking faults was drastically reduced by MEE.

TEM study of epitactically grown GaAs/ScxEr1−xAs/GaAs heterostructures

1990 ◽  
Vol 48 (4) ◽  
pp. 586-587
Author(s):  
Jane G. Zhu
Keyword(s):  
Crystal Structure ◽  
Lattice Mismatch ◽  
New Physics ◽  
Dark Field ◽  
Salt Crystal ◽  
Plan View ◽  
Weak Beam ◽  
Transmission Electron ◽  
Potential Applications ◽  
The Difference

The incorporation of metal layers into semiconductors is attracting growing attention due to potential applications in novel electronic devices and new physics of very thin metal films in semiconductors. This paper reports the growth of GaAs/ScxEr1−xAs/GaAs (x=0 and ∼0.3) on (100) GaAs substrates by molecular beam epitaxy (MBE) and the characterization of these heterostructures by transmission electron microscopy (TEM). ErAs, ScAs and many other rare-earth arsenides have the rock-salt crystal structure, which is different from the zinc-blende structure of GaAs. The difference in the crystal structure substantially affects the heteroepitactic growth. The lattice mismatch between ErAs (ScAs) and GaAs is 1.6% (-3.3%). Lattice-matched growth of ScxEr1−xAs/GaAs can be obtained at x=0.32. TEM has been used in this study extensively to characterize the microstructure and the growth-related defects. Both cross-section and plan-view samples have been studied using strong-beam, weak-beam dark-field and high-resolution imaging, as well as selected-area diffraction.

Characterization of Dislocations in GaAs Grown on Si and Ge

1987 ◽  
Vol 91 ◽  
Author(s):  
N.-H. Cho ◽  
S. Mckernan ◽  
C. B. Carter ◽  
B. C. De Cooman ◽  
K. Wagner
Keyword(s):  
Lattice Mismatch ◽  
Imaging Technique ◽  
Layer Structure ◽  
Misfit Dislocations ◽  
Structure Model ◽  
Polar Material ◽  
Weak Beam ◽  
Transmission Electron ◽  
Prepared Layer

ABSTRACTDislocations are produced at the interface between epilayers and the substrate when there is a lattice mismatch. When GaAs is grown on Ge substrates, these dislocations can propagate into the epilayers. They can then interact with one another or with antiphase boundaries which are generated when the polar-material is grown on a non-polar materials.The interactions between these defects have been investigated using the weak-beam imaging technique of transmission electron microscopy. Possible interactions between the misfit dislocations and heterojunctions were examined in a specially prepared layer structure model of GaAs-AlxGal−xAs.

A Novel TEM Technique for Characterizing As-Grown CVD Diamond Films

1991 ◽  
Vol 49 ◽  
pp. 956-957 ◽  
Author(s):  
Z.L. Wang ◽  
J. Bentley ◽  
R.E. Clausing ◽  
L. Heatherly ◽  
L.L. Horton
Keyword(s):  
Diamond Films ◽  
Chemical Vapor ◽  
Growth Direction ◽  
Dark Field ◽  
Growth Surface ◽  
Specimen Preparation ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
First Time ◽  
Microstructural Studies

Microstructural studies by transmission electron microscopy (TEM) of diamond films grown by chemical vapor deposition (CVD) usually involve tedious specimen preparation. This process has been avoided with a technique that is described in this paper. For the first time, thick as-grown diamond films have been examined directly in a conventional TEM without thinning. With this technique, the important microstructures near the growth surface have been characterized. An as-grown diamond film was fractured on a plane containing the growth direction. It took about 5 min to prepare a sample. For TEM examination, the film was tilted about 30-45° (see Fig. 1). Microstructures of the diamond grains on the top edge of the growth face can be characterized directly by transmitted electron bright-field (BF) and dark-field (DF) images and diffraction patterns.

Defects in β-SiC thin films grown on α-SiC substrates

1988 ◽  
Vol 46 ◽  
pp. 568-569
Author(s):  
Karren L. More
Keyword(s):  
Thin Films ◽  
Semiconductor Device ◽  
Lattice Mismatch ◽  
Chemical Vapor ◽  
Substrate Material ◽  
Growth Interface ◽  
Si Substrates ◽  
Thermal Expansion Coefficients ◽  
Device Applications ◽  
Expansion Coefficients

Beta-SiC is an ideal candidate material for use in semiconductor device applications. Currently, monocrystalline β-SiC thin films are epitaxially grown on {100} Si substrates by chemical vapor deposition (CVD). These films, however, contain a high density of defects such as stacking faults, microtwins, and antiphase boundaries (APBs) as a result of the 20% lattice mismatch across the growth interface and an 8% difference in thermal expansion coefficients between Si and SiC. An ideal substrate material for the growth of β-SiC is α-SiC. Unfortunately, high purity, bulk α-SiC single crystals are very difficult to grow. The major source of SiC suitable for use as a substrate material is the random growth of {0001} 6H α-SiC crystals in an Acheson furnace used to make SiC grit for abrasive applications. To prepare clean, atomically smooth surfaces, the substrates are oxidized at 1473 K in flowing 02 for 1.5 h which removes ∽50 nm of the as-grown surface. The natural {0001} surface can terminate as either a Si (0001) layer or as a C (0001) layer.

Influence of MBE Growth Conditions on Dislocation Densities of GaAs/Ge Epilayers Grown on Silicon Substrates

1985 ◽  
Vol 43 ◽  
pp. 364-365
Author(s):  
K.M. Hones ◽  
P. Sheldon ◽  
B.G. Yacobi ◽  
A. Mason
Keyword(s):  
High Efficiency ◽  
Lattice Mismatch ◽  
Low Cost ◽  
Growth Conditions ◽  
Nonradiative Recombination ◽  
Device Structure ◽  
Si Substrates ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dislocation Type

There is increasing interest in growing epitaxial GaAs on Si substrates. Such a device structure would allow low-cost substrates to be used for high-efficiency cascade- junction solar cells. However, high-defect densities may result from the large lattice mismatch (∼4%) between the GaAs epilayer and the silicon substrate. These defects can act as nonradiative recombination centers that can degrade the optical and electrical properties of the epitaxially grown GaAs. For this reason, it is important to optimize epilayer growth conditions in order to minimize resulting dislocation densities. The purpose of this paper is to provide an indication of the quality of the epitaxially grown GaAs layers by using transmission electron microscopy (TEM) to examine dislocation type and density as a function of various growth conditions. In this study an intermediate Ge layer was used to avoid nucleation difficulties observed for GaAs growth directly on Si substrates. GaAs/Ge epilayers were grown by molecular beam epitaxy (MBE) on Si substrates in a manner similar to that described previously.

Growth of hematite on (0001) and {1102} sapphire substrates

1990 ◽  
Vol 48 (4) ◽  
pp. 376-377
Author(s):  
Lisa A. Tietz ◽  
Scott R. Summerfelt ◽  
C. Barry Carter
Keyword(s):  
Imaging Techniques ◽  
Chemical Vapor ◽  
Interface Energy ◽  
Dark Field ◽  
Cation Sublattice ◽  
Sapphire Substrates ◽  
Dark Field Imaging ◽  
Weak Beam ◽  
Pressure Chemical ◽  
Interface Structures

Defects in thin films are often introduced at the substrate-film interface during the early stages of growth. The interface structures of semiconductor heterojunctions have been extensively studied because of the electrical activity of defects in these materials. Much less attention has been paid to the structure of oxide-oxide heterojunctions. In this study, the structures of the interfaces formed between hematite (α-Fe2O3) and two orientations of sapphire (α-Al2O3) are examined in relationship to the defects introduced into the hematite film. In such heterojunctions, the oxygen sublattice is expected to have a strong influence on the epitaxy; however, defects which involve only the cation sublattice may be introduced at the interface with little increase in interface energy.Oxide heterojunctions were produced by depositing small quantities of hematite directly onto electrontransparent sapphire substrates using low-pressure chemical vapor deposition. Prior to deposition, the ionthinned substrates were chemically cleaned and annealed at 1400°C to give “clean”, crystalline surfaces. Hematite was formed by the reaction of FeCl3 vapor with water vapor at 1150°C and 1-2 Torr. The growth of the hematite and the interface structures formed on (0001) and {102} substrates have been studied by bright-field, strong- and weak-beam dark-field imaging techniques.

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