Initial Strain Relaxation in S0.91Ge0.09/Si Superlattice Structures via Misfit-Dislocations

1999 ◽  
Vol 570 ◽  
Author(s):  
J. Leininger ◽  
G. D. U'ren ◽  
M. S. Goorsky
Keyword(s):  
Misfit Dislocation ◽  
Strain Relaxation ◽  
High Vacuum ◽  
Average Density ◽  
Dislocation Nucleation ◽  
Ultra High Vacuum ◽  
Initial Strain ◽  
Homogeneous Distribution ◽  
Misfit Dislocations ◽  
Dislocation Sources

ABSTRACTWe addressed the initial strain relaxation of symmetric 95 Å period Si0.91Ge0.09/Si heterostructures grown by ultra-high vacuum chemical vapor deposition on vicinal substrates miscut 2.04° from (001) in a direction 36° from a [110]. Double-axis x-ray topography revealed misfit-dislocation sources in the as-grown samples with an average density of about 60 cm−2, although the distribution of these sites was not homogeneous. The progression of dislocation nucleation and growth was observed during subsequent rapid thermal annealing (800°C, 20s-320s). Physical heterogeneities were identified as dislocation sources, and they gave rise to orthogonal misfit dislocation bundles, which on a macroscopic scale resemble crosses. Upon longer annealing, a more homogeneous distribution of defects was observed without measurable relaxation. These original defects did propagate; however, they did not spur a cross-slip multiplication sequence.

Mechanisms and Kinetics of Misfit Dislocation Formation in Heteroepitaxial Thin Films

1990 ◽  
Vol 188 ◽  
Author(s):  
W. D. Nix ◽  
D. B. Noble ◽  
J. F. Turlo
Keyword(s):  
Misfit Dislocation ◽  
Strain Relaxation ◽  
Dislocation Motion ◽  
Dislocation Nucleation ◽  
Dislocation Segment ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Film Substrate ◽  
Kinetics Of ◽  
Dislocation Formation

ABSTRACTThe mechanisms and kinetics of forming misfit dislocations in heteroepitaxial films are studied. The critical thickness for misfit dislocation formation can be found by considering the incremental extension of a misfit dislocation by the movement of a “threading” dislocation segment that extends from the film/substrate interface to the free surface of the film. This same mechanism allows one to examine the kinetics of dislocation motion and to illuminate the importance of dislocation nucleation and multiplication in strain relaxation. The effects of unstrained epitaxial capping layers on these processes are also considered. The major effects of such capping layers are to inhibit dislocation nucleation and multiplication. The effect of the capping layer on the velocity of the “threading” dislocation is shown to be small by comparison.A new substrate curvature technique for measuring the strain and studying the kinetics of strain relaxation in heteroepitaxial films is also briefly described.

“Barrierless” Misfit Dislocation Nucleation in SiGe/Si Strained Layer Epitaxy

1992 ◽  
Vol 263 ◽  
Author(s):  
D.D. Perovic ◽  
D.C. Houghton
Keyword(s):  
Activation Energy ◽  
Misfit Dislocation ◽  
Strain Relaxation ◽  
Dislocation Nucleation ◽  
Theoretical Treatment ◽  
Misfit Dislocations ◽  
Plan View ◽  
Strained Layer ◽  
Wide Range ◽  
Peierls Barrier

ABSTRACTThe study of the critical thickness/strain phenomenon inherent in metastable, layered heterostructures has led to the development of several models which describe elastic strain relaxation. Hitherto, the nucleation of misfit dislocations required for coherency breakdown is the least well understood aspect of strain relaxation, due to the paucity of experimental data. Moreover, existing theoretical calculations predict relatively large activation energy barriers (>10 eV) for misfit dislocation nucleation in relatively low misfit (<2%) systems. In this work it will be shown that the nucleation of misfit dislocations can occur spontaneously demonstrating a vanishingly small activation energy barrier. Specifically, experimental studies of a wide range of GexSi1−x/Si (x< 0.5) hetero-structures, grown by MBE and CVD techniques, have provided quantitative data from bulk specimens on the observed misfit dislocation nucleation rate and activation energy using large-area diagnostic techniques (eg. chemical etching/Nomarski microscopy). In parallel, the strained layer microstructure was studied in detail using crosssectional and plan-view electron microscopy in order to identify a new dislocation nucleation mechanism, the ‘double half-loop’ source. From the combined macroscopic and microscopic analyses, a theoretical treatment has been developed based on nucleation stress and energy criteria which predicts a “barrierless” nucleation process exists even at low misfits (< 1%). Accordingly, the observed misfit dislocation nucleation event has been found both experimentally and theoretically to be rate-controlled solely by Peierls barrier dependent, glide-activated processes with activation energies of ∼2 eV.

Observation of GaAs/Si Epitaxial Interfaces by Atomic Resolution Electron Microscopy

1986 ◽  
Vol 67 ◽  
Author(s):  
N. Otsuka ◽  
C. Choi ◽  
Y. Nakamura ◽  
S. Nagakura ◽  
R. Fischer ◽  
...  
Keyword(s):  
Substrate Surface ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Si Substrates ◽  
Voltage Electron ◽  
Resolution Electron ◽  
Gaas Films ◽  
Substrate Surfaces

ABSTRACTRecent studies have shown that high quality GaAs films can be grown by MBE on Si substrates whose surfaces are slightly tilted from the (100) plane. In order to investigate the effect of the tilting of substrate surfaces on the formation of threading dislocations, the GaAs/Si epitaxial interfaces have been observed with a 1 MB ultra-high vacuum, high voltage electron microscope. Two types of misfit dislocations, one with Burgers vectors parallel to the interface and the other with Burgers vectors inclined from the interface, were found in these epitaxial interfaces. The observation of crosssectional samples perpendicular to each other has shown that the tilting of the substrate surface directly influences the generation of these two types of misfit dislocations. The mechanism of the reduction of threading dislocations by the tilting of the substrate surface is discussed based on these observations.

In Situ Electron Microscopy Studies of Surface Dynamical Processes

1998 ◽  
Vol 4 (S2) ◽  
pp. 608-609
Author(s):  
Ruud M. Tromp
Keyword(s):  
Electron Microscopy ◽  
Strain Relaxation ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Relaxation Phase ◽  
Transmission Electron ◽  
In Situ Electron Microscopy ◽  
Low Energy Electron ◽  
New Machine

To obtain a full and detailed understanding of the spatiotemporal dynamics of surface processes such as epitaxial growth, strain relaxation, phase transformations and phase transitions, chemisorption and etching, in situ real-time observations have proven to be invaluable. The development of two experimental techniques, i.e. Low Energy Electron Microscopy (LEEM) typically operating at electron energies below 10 eV, and Ultra-High-Vacuum Transmission Electron Microscopy (UHV-TEM) at several 100 keV, has made such in situ studies routinely possible. In many cases, the videodata obtained from such experiments are amenable to detailed, quantitative analysis, yielding statistical, kinetic and thermodynamic information that cannot be obtained in any other way.I will discuss recent experimental developments, including the design and construction of a new and improved LEEM instrument. Figure 1 shows a schematic diagram of this new machine. There are several features that distinguishes this design from most other LEEMs. One is the use of a 90 degree deflection magnetic prism array,

The Role of Misfit Dislocation During Epitaxial Growth

1987 ◽  
Vol 94 ◽  
Author(s):  
D. Cherns
Keyword(s):  
Misfit Dislocation ◽  
Lattice Spacing ◽  
Minimum Energy ◽  
Energy Criterion ◽  
Misfit Dislocations ◽  
Metal Metal ◽  
Correct Account ◽  
Pseudomorphic Growth ◽  
Dislocation Sources

ABSTRACTThe theory of Frank and van der Merwe (FM) in 1949 showed that a minimum energy criterion could explain the pseudomorphic growth of a deposit on a substrate of different lattice spacing and the subsequent relief of strain by misfit dislocations as the deposit thickness increases. Although the “equilibrium” theory is qualitatively correct, account must be taken of actual dislocation sources, which may be complex, and which may be more or less efficient for misfit relief than predicted by the FM model. Moreover, misfit dislocation sources may determine the morphology of the growing film, the interface topology and even the atomic structure of the deposit/substrate interface. These various roles of misfit dislocations are reviewed here with examples from work on metal/metal, semiconductor/semiconductor and metal/semiconductor systems.

Rapid Thermal Processing of Buried Sil−xGex Strained Layers; Photoluminescence Decay and Misfit Dislocation Generation.

1990 ◽  
Vol 198 ◽  
Author(s):  
D.C. Houghton ◽  
N.L. Rowell
Keyword(s):  
Quantum Wells ◽  
Misfit Dislocation ◽  
Thermal Processing ◽  
Internal Quantum Efficiency ◽  
Dislocation Nucleation ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Dislocation Generation ◽  
Strained Layers ◽  
Wide Range

ABSTRACTThe thermal constraints for device processing imposed by strain relaxation have been determined for a wide range of Si-Ge strained heterostructures. Misfit dislocation densities and glide velocities in uncapped Sil-xGex alloy layers, Sil-xGex single and multiple quantum wells have been measured using defect etching and TEM for a range of anneal temperatures (450°C-1000°C) and anneal times (5s-2000s). The decay of an intense photoluminescence peak (∼ 10% internal quantum efficiency ) from buried Si1-xGex strained layers has been correlated with the generation of misfit dislocations in adjacent Sil-xGex /Si interfaces. The misfit dislocation nucleation rate and glide velocity for all geometries and alloy compositions (0<x<0.25) were found to be thermally activated processes with activation energies of (2.5±0.2)eV and (2.3-0.65x)eV, respectively. The time-temperature regime available for thermal processing is mapped out as a function of dislocation density using a new kinetic model.

A Multiplication Mechanism for Misfit Dislocations

1992 ◽  
Vol 263 ◽  
Author(s):  
Michael A. Capano
Keyword(s):  
Dislocation Loop ◽  
Misfit Dislocation ◽  
Epitaxial Layers ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Sequential Process ◽  
Single Dislocation ◽  
Dislocation Arrays ◽  
Half Loop ◽  
Dislocation Sources

ABSTRACTA new mechanism which describes how misfit dislocations in epitaxial layers multiply is presented. This work demonstrates how a single threading dislocation can give rise to an array of dislocation sources, where each source generates a single dislocation loop perpendicular to the primary misfit dislocation. As a threading dislocation with pure screw character glides through an epilayer, certain processes occur which lead to the production of a single dislocation half-loop, and the regeneration of the original threading dislocation. The regenerated threading dislocation continues to propagate on its primary glide plane, which allows the process to repeat itself at some later time. The result of this sequential process is an array of half-loops perpendicular to the primary misfit dislocation. The shape and symmetry of the arrays also contains information regarding how the mechanism operates. The proposed mechanism is related to misfit dislocation arrays in a single Si0.87Ge0.13 layer on Si(001).

The Roles of Stress, Geometry and Orientation on Misfit Dislocations Kinetics and Energetics in Epitaxial Strained Layers.

1991 ◽  
Vol 239 ◽  
Author(s):  
R. Hull ◽  
J. C. Bean ◽  
F. Ross ◽  
D. Bahnck ◽  
L. J. Pencolas
Keyword(s):  
Misfit Dislocation ◽  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Misfit Dislocations ◽  
Slip Systems ◽  
Strained Layers ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Strain Stress ◽  
Kinetics Of

ABSTRACTThe geometries, microstructures, energetics and kinetics of misfit dislocations as functions of surface orientation and the magnitude of strain/stress are investigated experimentally and theoretically. Examples are drawn from (100), (110) and (111) surfaces and from the GexSi1–x/Si and InxGa1–x/GaAs systems. It is shown that the misfit dislocation geometries and microstructures at lattice mismatch stresses < - 1GPa may in general be predicted by operation of the minimum magnitude Burgers vector slipping on the widest spaced planes. At stresses of the order several GPa, however, new dislocation systems may become operative with either modified Burgers vectors or slip systems. Dissociation of totál misfit dislocations into partial dislocations is found to play a crucial role in strain relaxation, on surfaces other than (100) under compressive stress.

Thermal Stability of Si/Si0.85Ge0.15/Si Modulation Doped Double Heterostructures

1989 ◽  
Vol 160 ◽  
Author(s):  
P.J. Wang ◽  
B.S. Meyerson ◽  
P.M. Fahey ◽  
F. LeGoues ◽  
G.J. Scilla ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Ultra High Vacuum ◽  
Misfit Dislocations ◽  
Two Dimensional ◽  
Double Heterostructures ◽  
Vapor Deposition Technique ◽  
P Type ◽  
Thermal Stability Of

AbstractThe thermal stability of Si/Si0.85Ge0.15/Si p-type modulation doped double heterostructures grown by the Ultra High Vacuum/ Chemical Vapor Deposition technique has been examined by Hall measurement, transmission electron microscopy, secondary ion mass spectroscopy, and Raman spectroscopy. As deposited heterostructures showed two-dimensional hole gas formation at the abrupt Si/SiGe and SiGe/Si interfaces. Annealing at 800 °C. for 1 hr. caused the diffusion of boron acceptors to the heterointerfaces, degrading the hole mobilities observed in the two dimensional hole gas. Rapid redistribution of boron, causing a loss of the 2 dimensional carrier behavior, was observed after a 900 °C, 0.5 hr. anneal. Neither Ge interdiffusion nor the generation of misfit dislocations were observed in the annealed heterostructures, evincing the defect-free crystal quality of these as-grown strained heteroepitaxial layers. The superior stability of these heterostructures have strong positive implications for Si:Ge heterojunction devices.

Comparison of Growth and Strain Relaxation of Si/Ge Superlattices Under Compressive and Tensile Strain Field

1991 ◽  
Vol 220 ◽  
Author(s):  
Werner Wegscheider ◽  
Karl Eberl ◽  
Gerhard Abstreiter ◽  
Hans Cerva ◽  
Helmut Oppolzer
Keyword(s):  
Growth Parameters ◽  
Strain Relaxation ◽  
Dislocation Nucleation ◽  
Misfit Dislocations ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Short Period ◽  
Low Energy Electron ◽  
Superlattice Period

ABSTRACTOptimization of growth parameters of short period Si/Ge superlattices (SLs) has been achieved via in situ low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) measurements during homo- and heteroepitaxy on Si (001) and Ge (001) substrates. Transmission electron microscopy (TEM) reveals that pseudomorphic SimGe12-m (m = 9 and 3 for growth on Si and Ge, respectively) SLs with extended planar layering can be prepared almost defect-free by a modified molecular beam epitaxy (MBE) technique. Whereas the SLs on Ge can be deposited at a constant substrate temperature, high-quality growth on Si demands for temperature variations of more than 100°C within one superlattice period. Strain relaxation of these SLs with increasing number of periods has been directly compared by means of TEM. For the compressively strained structures grown on Si we found misfit dislocations of the type 60° (a/2)<110>. Under opposite strain conditions i.e. for growth on Ge, strain relief occurs only by microtwin formation through successive glide of 90° (a/6)<211> Shockley partial dislocations. This is consistent with a calculation of the activation energy for both cases based on a homogeneous dislocation nucleation model.

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