Island Formation in Ge on Si Heteroepitaxy

1990 ◽  
Vol 198 ◽  
Author(s):  
D.J. Eaglesham ◽  
H.-J. Gossmann ◽  
M. Cerullo
Keyword(s):  
Growth Temperature ◽  
Driving Force ◽  
Island Formation ◽  
Growth Dislocation ◽  
Edge Dislocations ◽  
2D To 3D

ABSTRACTWe present a study of island formation (the transition from 2D to 3D growth) during the Stranski-Krastanow (S-K) growth of Ge on Si. The energetic driving force for S-K island formation should be the ability to relax the islands by dislocation introduction. Here, we show that Ge islands formed on Si (100) are initially dislocation-free, in the presence of a 2D “sea” that is far in excess of the equilibrium 3 monolayers (ML). We call this phase of growth “dislocation-free S-K”. The 2-D sea does not collapse until dislocated islands are produced at an average coverage of = 7 ML. We call the dislocation-free island phase “coherent S-K” growth. The corresponding 2D-3D transition on Si (111) appears to reach equilibrium far faster, and we have not observed dislocation-free island formation: dislocated islands are seen at = 5 ML. As expected, the kinetics allow us to suppress island formation on (100) by reducing the growth temperature. These thick 2D films are analogous to those grown on As-covered surfaces, but have a microstructure dominated by edge dislocations.

Study of the Origin of Misorientation in GaN Grown by Pendeo-Epitaxy

2002 ◽  
Vol 743 ◽  
Author(s):  
D. N. Zakharov ◽  
Z. Liliental-Weber ◽  
A. M. Roskowski ◽  
S. Einfeldt ◽  
R. F. Davis
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Density ◽  
Growth Temperature ◽  
Threading Dislocations ◽  
Transmission Electron ◽  
Edge Dislocations ◽  
Seed Layers

ABSTRACTGrowth of pendeo-epitaxial (PE) layers introduces misorientation between the seed layers and the overgrown wing layers. The origin of this misorientation has been studied by Transmission Electron Microscopy (TEM) using a set of samples in which subsequent procedures utilized in PE were applied, i.e. growth of GaN template, stripe etching, annealing at the growth temperature of the PE layers and final PE growth. It was shown that etching of seed-stripes did not change the type of defects or their distribution. However, heating to the PE growth temperature drastically modified the surface and V-shaped pits were formed. The surface became smooth again after the PE growth took place. Overgrowth of the V-shaped pits resulted in formation of edge threading dislocations over a seed-stripe region with a dislocation density of 8.0×108 cm−2. Formation of new edge dislocations over the seed can have an influence on the misorientation between the PE grown regions.

Kinetic Aspects of Island Nucleation Derived from Near Equilibrium Growth Experiments

1999 ◽  
Vol 583 ◽  
Author(s):  
S. H. Christiansen ◽  
M. Becker ◽  
H. Wawra ◽  
M. Albrecht ◽  
H. P. Strunk
Keyword(s):  
Growth Temperature ◽  
Growth Rates ◽  
Driving Forces ◽  
Substrate Surface ◽  
High Growth ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Island Formation ◽  
Island Nucleation ◽  
Equilibrium Growth

AbstractUsing liquid phase epitaxy from Bi solution, a by its nature a near equilibrium growth process, we study the kinetics of island formation in the heteroepitaxial system SiGe/Si(001) as dependent on growth temperature, growth rate and composition (which also determines the lattice misfit between layer and substrate). As a main result island formation can be described by classical nucleation theory, moreover, it can be described as any other crystallization process such as solid state crystallization of amorphous silicon or crystallization from a melt, provided that the limited size the islands can grow into is correctly considered. In consequence, after an incubation time period that depends on the growth temperature, islands nucleate and cover the substrate surface with time. The activation energy of island nucleation is 0.84±0.13eV. The coverage with islands depends only on the undercooling and is independent of the cooling rate in case near equilibrium growth conditions are maintained. In these cases the islands have the shape of truncated pyramids with four {111}– side facets and a base width λ that only depends on the misfit f (λ ∝ 1/f2). Deviations from the equilibrium growth stage at high growth rates (thus higher growth driving forces) result in the formation of a higher density of smaller islands with smaller facet angles. At higher growth rates, some kinetic influences begin to appear indicated by the additional appearance of shallower pyramids with four {115}– facet side faces.

Shape Transition in Self-Organized InAs/InP Nanostructures

2001 ◽  
Vol 696 ◽  
Author(s):  
H.R. Gutiérrez ◽  
M.A. Cotta ◽  
M.M.G. de Carvalho
Keyword(s):  
Growth Temperature ◽  
Driving Force ◽  
Anisotropic Diffusion ◽  
Chemical Potential ◽  
Quantum Wires ◽  
Shape Transition ◽  
Self Organized ◽  
Self Assembled ◽  
Inp Substrates ◽  
Stable Shape

AbstractIn this letter we report the transition from self-assembled InAs quantum-wires to quantumdots grown on (100) InP substrates. This transition is obtained when the wires are annealed at the growth temperature. Our results suggest that the quantum-wires are a metastable shape originated from the anisotropic diffusion over the InP buffer layer during the formation of the first InAs monolayer. The wires evolve to a more stable shape (dot) during the annealing. The driving force for the transition is associated with variations in the elastic energy and hence in the chemical potential produced by height fluctuations along the wire. The regions along the wires with no height variations are more stable allowing the formation of complex, self-assembled nanostructures such as dots interconnected by wires.

Current Status of the Quality of 4H-SiC Substrates and Epilayers for Power Device Applications

MRS Advances ◽  
2016 ◽  
Vol 1 (2) ◽  
pp. 91-102 ◽  
Author(s):  
M. Dudley ◽  
H. Wang ◽  
Jianqiu Guo ◽  
Yu Yang ◽  
Balaji Raghothamachar ◽  
...  
Keyword(s):  
Relaxation Process ◽  
Epitaxial Growth ◽  
Driving Force ◽  
Lattice Parameter ◽  
Current Status ◽  
Concentration Difference ◽  
Before And After ◽  
Half Loop ◽  
Device Applications ◽  
Edge Dislocations

ABSTRACTInterfacial dislocations (IDs) and half-loop arrays (HLAs) present in the epilayers of 4H-SiC crystal are known to have a deleterious effect on device performance. Synchrotron X-ray Topography studies carried out on n-type 4H-SiC offcut wafers before and after epitaxial growth show that in many cases BPD segments in the substrate are responsible for creating IDs and HLAs during CVD growth. This paper reviews the behaviors of BPDs in the substrate during the epitaxial growth in different cases: (1) screw-oriented BPD segments intersecting the surface replicate directly through the interface during the epitaxial growth and take part in stress relaxation process by creating IDs and HLAs (Matthews-Blakeslee model [1] ); (2) non-screw oriented BPD half loop intersecting the surface glides towards and replicates through the interface, while the intersection points convert to threading edge dislocations (TEDs) and pin the half loop, leaving straight screw segments in the epilayer and then create IDs and HLAs; (3) edge oriented short BPD segments well below the surface get dragged towards the interface during epitaxial growth, leaving two long screw segments in their wake, some of which replicate through the interface and create IDs and HLAs. The driving force for the BPDs to glide toward the interface is thermal stress and driving force for the relaxation process to occur is the lattice parameter difference at growth temperature which results from the doping concentration difference between the substrate and epilayer.

Surface nucleated half-loops in strained epilayers

1990 ◽  
Vol 48 (4) ◽  
pp. 560-561
Author(s):  
Eric P. Kvam
Keyword(s):  
Growth Temperature ◽  
Critical Thickness ◽  
Three Dimensional ◽  
Mechanical Damage ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Dislocation Type ◽  
Dimensional Growth ◽  
Edge Dislocations

Mismatched epilayers, grown beyond some critical thickness, have commonly been observed to have arrays of misfit-relieving dislocations at the heterointerface. In diamond or sphalerite structures, these arrays are orthogonal <110> networks of long 60° type dislocations, which are glissile and have inclined Burgers vectors. Up to the point at which growth becomes three-dimensional (about 2% mismatch in the (In,Ga)As/GaAs system), internal defects act as the sources for the misfit dislocations. Examples of such sources include pre-existing threading dislocations, internal loops, precipitates, and mechanical damage.In higher mismatch two-dimensional growth, such as can be produced in the GeSi/Si(001) system, the density of epithreading dislocations suddenly increases as the length of interfacial misfit dislocations falls. Almost simultaneously, the misfit dislocation type changes from 60° to edge. While in-situ hot stage experiments have shown that 60° type dislocations become mobile at about the growth temperature of the epilayer, and have observable velocities from this temperature on up, our observations of edge dislocations in the same system have shown that velocities for edge dislocations are essentially nil (measurable limit <lnm/s) even at 750°C, some 200°C above the growth temperature.

Structure and Orientation of As Precipitates in LT-MBE Grown GaAs

1991 ◽  
Vol 49 ◽  
pp. 900-901 ◽  
Author(s):  
Alain Claverie ◽  
Zuzanna Liliental-Weber
Keyword(s):  
Transport Properties ◽  
Layer Thickness ◽  
Growth Temperature ◽  
Low Temperatures ◽  
Lattice Parameter ◽  
Crystalline Quality ◽  
Insulating Properties ◽  
Lt Gaas

GaAs layers grown by MBE at low temperatures (in the 200°C range, LT-GaAs) have been reported to have very interesting electronic and transport properties. Previous studies have shown that, before annealing, the crystalline quality of the layers is related to the growth temperature. Lowering the temperature or increasing the layer thickness generally results in some columnar polycrystalline growth. For the best “temperature-thickness” combinations, the layers may be very As rich (up to 1.25%) resulting in an up to 0.15% increase of the lattice parameter, consistent with the excess As. Only after annealing are the technologically important semi-insulating properties of these layers observed. When annealed in As atmosphere at about 600°C a decrease of the lattice parameter to the substrate value is observed. TEM studies show formation of precipitates which are supposed to be As related since the average As concentration remains almost unchanged upon annealing.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

The nucleation of cavities at grain boundaries

1987 ◽  
Vol 45 ◽  
pp. 288-291
Author(s):  
P. J. Goodhew
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Grain Boundaries ◽  
Radiation Damage ◽  
Impurity Concentration ◽  
Driving Force ◽  
Nucleation And Growth ◽  
Phase Boundaries ◽  
Cavity Nucleation ◽  
Spherical Bubble

Cavity nucleation and growth at grain and phase boundaries is of concern because it can lead to failure during creep and can lead to embrittlement as a result of radiation damage. Two major types of cavity are usually distinguished: The term bubble is applied to a cavity which contains gas at a pressure which is at least sufficient to support the surface tension (2g/r for a spherical bubble of radius r and surface energy g). The term void is generally applied to any cavity which contains less gas than this, but is not necessarily empty of gas. A void would therefore tend to shrink in the absence of any imposed driving force for growth, whereas a bubble would be stable or would tend to grow. It is widely considered that cavity nucleation always requires the presence of one or more gas atoms. However since it is extremely difficult to prepare experimental materials with a gas impurity concentration lower than their eventual cavity concentration there is little to be gained by debating this point.

Transmission Electron Microscopy characterization of epitaxial III-V semiconductor thin films grown on Si(100) by ion-assisted deposition

1990 ◽  
Vol 48 (4) ◽  
pp. 686-687
Author(s):  
L. Hultman ◽  
C.-H. Choi ◽  
R. Kaspi ◽  
R. Ai ◽  
S.A. Barnett
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Irradiation ◽  
High Energy ◽  
Nucleation Mechanism ◽  
Layer By Layer ◽  
Extended Defect ◽  
Island Formation ◽  
Si Substrates ◽  
Transmission Electron

III-V semiconductor films nucleate by the Stranski-Krastanov (SK) mechanism on Si substrates. Many of the extended defects present in the films are believed to result from the island formation and coalescence stage of SK growth. We have recently shown that low (-30 eV) energy, high flux (4 ions per deposited atom), Ar ion irradiation during nucleation of III-V semiconductors on Si substrates prolongs the 1ayer-by-layer stage of SK nucleation, leading to a decrease in extended defect densities. Furthermore, the epitaxial temperature was reduced by >100°C due to ion irradiation. The effect of ion bombardment on the nucleation mechanism was explained as being due to ion-induced dissociation of three-dimensional islands and ion-enhanced surface diffusion.For the case of InAs grown at 380°C on Si(100) (11% lattice mismatch), where island formation is expected after ≤ 1 monolayer (ML) during molecular beam epitaxy (MBE), in-situ reflection high-energy electron diffraction (RHEED) showed that 28 eV Ar ion irradiation prolonged the layer-by-layer stage of SK nucleation up to 10 ML. Otherion energies maintained layer-by-layer growth to lesser thicknesses. The ion-induced change in nucleation mechanism resulted in smoother surfaces and improved the crystalline perfection of thicker films as shown by transmission electron microscopy and X-ray rocking curve studies.

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