Generation Of Misfit Dislocations Research Articles

Strain relaxation from annealing of SiGe heterostructures for qubits

The misfit dislocation formation related to plastic strain relaxation in Si or Ge quantum well layers in SiGe heterostructures for spin qubits tends to negatively affect the qubit behaviors. Therefore, it is essential to understand and then suppress the misfit dislocation formation in the quantum well layers in order to achieve high-performance qubits. In this work, we studied the misfit dislocation propagation kinetics and interactions by annealing the strained Si or Ge layers grown by molecular beam epitaxy. The annealing temperatures are from 500 to 600 °C for Si layers and from 300 to 400 °C for Ge layers. The misfit dislocations were investigated by electron channeling contrast imaging. Our results show that the misfit dislocation propagation is a thermally activated process. Alongside, the blocking and unblocking interactions during misfit dislocations were also observed. The blocking interactions will reduce the strain relaxation according to theoretical calculation. These observations imply that it is possible to suppress the misfit dislocation formation kinetically by reducing the temperatures during the SiGe heterostructure epitaxy and post-epitaxy processes for developing well-functional SiGe-based spin qubits.

The transition of growth behaviors of moderate Sn fraction Ge1-xSnx (8 % < x < 15 %) epilayers with low temperature molecular beam epitaxy

Epitaxial breakdown phenomenon for Ge1-xSnx thin film with Sn fraction of less than 6 % during low-temperature molecular beam epitaxy has been reported [J. Appl. Phys. 97, 044904, 2005]. However more Sn incorporation is required for direct bandgap transition of GeSn alloy, which has much attractive for GeSn optoelectronic devices. In this work, moderate Sn fraction Ge1-xSnx (8 %∼15.3 %), as well as composition-stepped multiple GeSn layers, grown on Ge (001) substrate by molecular beam epitaxy at 120–150 ℃ are investigated. Epitaxy breakdown occurs for the Ge1-xSnx epilayer with Sn fraction of about 8 % and 10 %, even with low Sn fraction buffer layers, in which the film delaminates into a fully compressively strained bottom layer with dislocation free and a fully relaxed top layer spontaneously. Once the epitaxy breakdown occurs, the amorphous columnar structures extend into the following deposited GeSn epilayer, regardless of Sn fraction. While, the strain in the whole Ge1-xSnx epilayer with Sn fraction of 15.3 % is directly released during growth by generation of misfit and threading dislocations or agglomeration of islands. Those results indicate that there are three growth modes including fully compressive strained thin GeSn epilayer, epitaxial breakdown induced self-delamination of GeSn layer with moderate Sn fraction, and strain relaxed Ge1-xSnx epilayer with high Sn fraction of above 15 %. The complex behavior can be attributed to the competition between kinetic roughening and strain- driven GeSn agglomeration or generation of dislocations. The understanding of the growth behavior is helpful for controlling crystal quality of GeSn thin films for their application in optoelectronic devices.

Viewing SiGe Heterostructure for Qubits with Dislocation Theory

SiGe/Si/SiGe heterostructure serves as one of the ideal semiconductor material system to build large scale electron spin qubits[1]. To further push the scalability and extend the coherence times of qubits built on SiGe/Si/SiGe heterostructures, there are several factors to improve, one of that is the lattice homogeneity of strained Si. One source of lattice homogeneity break down are dislocations. Due to the difficulties of high quality SiGe bulk crystal growth [2-3], relaxed SiGe is commonly grown on Si substrates by epitaxy. Viewing the SiGe/Si/SiGe heterostructure on native Si substrate, dislocations half loops form unavoidably because of the misfit between SiGe and the Si substrate. These dislocation half loops consist of threading segments extending through the whole heterostructure (figure 1 (a) and (c)) [4]. Due to the stress caused by the strained Si quantum well layer, the threading dislocations can be driven to glide, resulting in additional misfit segments in the lower interface of strained Si layer when the critical thickness is exceeded (figure 1 (b)) [5]. The extension of these misfit segments is blocked when they meet other perpendicular dislocations (figure 1 (d)) [6]. These misfit dislocations destroy strain uniformity and cause tilt inside the Si layer, resulting in a distortion of the valley splitting and ultimately, reducing the coherence time of qubits [7-8].In this work, we present the observation of dislocations in SiGe/Si/SiGe heterostructures for qubit application by plan-view TEM (Figure 1 (right)). Here, the experimental observations agree with dislocation theory that threading dislocations (some are marked by (b)) will glide and elongate to have misfit segments (some are marked by (c)) in the interface when two requirements are fulfilled: misfit exists between epitaxial layer and substrate; critical thickness is exceeded. When the misfit dislocations meet perpendicular misfit dislocation line, they are blocked since the thickness is not enough to glide over it [6]. This is the case in figure 1 right marked by (d). Due to the misfit segment generation and blocking effects, the misfit dislocation spacing is proportional to the threading dislocation density both theoretically and experimentally. These misfit dislocations bring local strain field around them [9], which disturb the desired homogeneous strain field by misfit. Therefore, misfit dislocation generation needs to be suppressed if one wants to achieve homogeneous strain in Si thin layer in large scale.According to Matthews-Blakeslee theory, one can avoid the formation of misfit dislocations in the Si interface by controlling the strained layer within the critical thickness. The critical thickness of Si on Si0.7Ge0.3 is calculated as 8.5 nm. The Electron channeling contrast images of Si with difference thickness 10 nm and 5 nm grown on high threading dislocation relaxed Si0.7Ge0.3 buffer at 700°C by reduced pressure chemical vapor deposition in Figure 2 are collaborating with theory: obviously misfit dislocation appear in 10 nm Si on relaxed Si0.7Ge0.3 (Figure 2 (left)) and no misfit dislocation are presented in 5 nm Si on Si0.7Ge0.3 (Figure 2 (right)).Our results show that dislocation generation and movement needs to be taken into consideration to further develop SiGe heterostructure based qubits.

Enhanced photoluminescence of GeSn by strain relaxation and spontaneous carrier confinement through rapid thermal annealing

In this work, the structural evolution and photoluminescence (PL) of 200 nm pseudomorphic Ge 0.9338 Sn 0.0662 on Ge (001) substrate grown by low-temperature molecular beam epitaxy (MBE) after rapid thermal annealing (RTA) is studied. Under RTA at 350 °C or lower, the GeSn film is coherently strained on Ge substrate. As RTA temperature further increases, gradual strain relaxation of GeSn is enabled by generation of misfit dislocations and threading dislocations. As RTA temperature reaches 550 °C or beyond, Sn segregation occurs along with strain relaxation. The PL intensity of annealed samples is enhanced compared to that of as-grown sample probably due to improved crystal quality and strain relaxation (for RTA at> 350 °C) of GeSn. The sample annealed at 500 °C exhibits highest PL intensity due to formation of a Sn-component-graded (SCG) heterojunction with highest Sn content in surface region resulted from interdiffusion of Ge and Sn. The formation of SCG heterojunction renders spontaneous confinement of optically pumped carriers in the surface region and enlarges occupation probability of carriers in Γ valley. Additionally, the carrier confinement in the surface region reduces self-absorption of GeSn and suppresses nonradiative recombination near the GeSn/Ge interface. The results manifest that RTA is an appropriate approach to improve the light emitting property of GeSn grown by low-temperature MBE. • Strain relaxation of pseudomorphic GeSn on Ge is realized by rapid thermal annealing. • A Sn-component-graded heterojunction is formed after rapid thermal annealing. • The light emitting property of GeSn is dramatically enhanced.

Thickness-dependent behavior of strain relaxation and Sn segregation of GeSn epilayer during rapid thermal annealing

The behavior of strain relaxation and Sn segregation of GeSn epilayers during growth and thermal annealing is very complex depending on the growth method, thickness and Sn content of the GeSn epilayer. Herein, we report on the thickness-dependent behavior of fully strained Ge1-xSnx epilayers (x = 0.097) on Ge (100) substrate grown by molecular beam epitaxy during rapid thermal annealing (RTA). It is found that when the GeSn epilayer is thinner than the critical thickness at Sn segregation temperature (hc(Ts)), GeSn epilayers would hardly be relaxed before Sn segregation during RTA. While for GeSn epilayer thicker than the hc(Ts), GeSn epilayers will undergo the process of strain relaxation before Sn segregation. The results indicate that the competition between Sn segregation and strain relaxation by generation of misfit dislocations strongly depends on the thickness of GeSn epilayers. A semi-quantitative model is proposed to explain the priority of Sn segregation or strain relaxation during RTA in terms of temperature-dependent critical thickness, which can be used to guide the design of strain-relaxed GeSn epilayer without Sn segregation for optoelectronic device application.

Numerical estimation of lattice strain, bending and generation of misfit dislocations in CdHgTe heterostructures grown on GaAs substrate

Using our own computer program, we determined the spatial distribution of lattice strains in the HgCdTe heterostructure grown on a GaAs substrate. Lattice stress resulting from lattice mismatch between the substrate and the epitaxial layer and bending of the heterostructure is almost completely relaxed by misfit dislocations forming matrixes in the interfaces’ areas. The average distances between dislocation lines in individual interfaces were calculated based on the minimum energy, i.e. elastic energy condition resulting from the interaction of stress fields and deformations caused by lattice misfit, bending and the presence of dislocation plus electrical energy of dislocations.

Atomic-scale study of precipitates (NbC and Cu-rich phase) at the twin boundary in the long time ageing austenitic stainless steel

ABSTRACT Microstructures of Cu-rich phases and NbC precipitated phases have been studied in a long time ageing austenitic stainless steel by high resolution scanning transmission electron microscopy. The interaction difference between the twins and the second phases found to be dependent on the nature of the precipitates. The Cu-rich phases were identified to be twinned at the twin boundary. Nevertheless, the NbC precipitates not only twinned at the twin boundary but also induced the twin boundary bypass them. A particle size dependence of the generation of misfit dislocations also was detected at interface between precipitates and the austenitic matrix.

Generation of misfit dislocations in a core-shell nanowire near the edge of prismatic core

The misfit strain relaxation via generation of partial and perfect misfit dislocations and their dipoles at the interface in core-shell nanowires with faceted cores is considered. The core has the shape of a long parallelepiped of a square cross-section and is placed symmetrically with respect to the cylindrical shell surface. The energy change caused by dislocation generation in such nanowires is calculated. Critical conditions for the onset of such dislocations are calculated and analyzed. The energy barriers for the dislocation generation are defined with respect to different values of the nanowire parameters. The preference of dislocation configuration and generation sites in the nanowire are determined.

Generation of Misfit Dislocations in a Core-Shell Nanowire Near the Edge of Prismatic Core

The misfit strain relaxation via generation of partial and perfect misfit dislocations and their di-poles at the interface in core-shell nanowires with faceted cores is considered. The core has the shape of a long parallelepiped of a square cross-section and placed symmetrically with respect to the cylindrical shell surface. The energy change caused by dislocation generation in such nanowires is calculated. Critical conditions for the onset of such dislocations are calculated and analyzed. The energy barriers for the dislocation generation are defined with respect to different values of the nanowire parameters. The preference of dislocation configuration and generation sites in the nanowire are determined.

Circular loops of misfit dislocations in decahedral core-shell nanoparticles

A theoretical model is proposed for stress relaxation in decahedral core-shell nanoparticles through formation of circular prismatic misfit dislocation loops at the core-shell interface. The critical conditions for stress relaxation are determined and discussed in comparison with those for single-crystalline core-shell nanoparticles. It is shown that decahedral core-shell nanoparticles should be less stable with respect to misfit dislocation generation than single-crystalline ones when the lattice parameter of the core is larger than that of the shell. Theoretical results are compared with experimental observations available in the literature and are shown to be in a good agreement with the latter.

Evidence of relationship between strain and In-incorporation: Growth of N-polar In-rich InAlN buffer layer by OMCVD

Two InxAl1−xN layers were grown simultaneously on different substrates [sapphire (0001) and the Ga-polar GaN template], but under the same reactor conditions, they were employed to investigate the mechanism of strain-driven compositional evolution. The resulting layers on different substrates exhibit different polarities and the layer grown on sapphire is N-polar. Moreover, for the two substrates, the difference in the degree of relaxation of the grown layers was almost 100%, leading to a large In-molar fraction difference of 0.32. Incorporation of In in InxAl1−xN layers was found to be significantly influenced by the strain imposed by the under-layers. With the evolutionary process of In-incorporation during subsequent layer growth along [0001], the direction of growth was investigated in detail by Auger electron spectroscopy. It is discovered that the In0.60Al0.40N layer grown directly on sapphire consists of two different regions with different molar fractions: the transition region and the uniform region. According to the detailed cross-sectional transmission electron microscopy, the transition region is formed near the hetero-interface due to the partial strain release caused by the generation of misfit-dislocations. The magnitude of residual strain in the uniform region decides the In-molar fraction. InxAl1−xN layers were analyzed by structural and optical characterization techniques. Our present work also shows that a multi-characterization approach to study InxAl1−xN is a prerequisite for their applications as a buffer layer.

Rapid onset of strain relief by massive generation of misfit dislocations in Bi(111)/Si(001) heteroepitaxy

Strain and its relaxation in lattice mismatched heterostructures are crucial for the functionality of modern electronic devices, which are often challenging to determine experimentally. Here, we demonstrate a technique for measuring the strain state during epitaxial growth of Bi(111) films on Si(001) by using the spot profile analysis low-energy electron diffraction. Exploiting two non-equivalent integer-order diffraction spots originated from two Bi sub-lattices, the lattice parameter of the film is determined with high precision, which allows tracing the strain state as the film grows. The sudden and massive generation of misfit dislocations is found at a critical thickness of 4 nm which is explained through the inhomogeneous strain state of films with a thickness below one quarter of the mean distance of the dislocations.

Dislocation Interaction and V-Shaped Growth of the Distorted Structure During Nanoindentation of Cu20Ni20Al20Co20Fe20 (high-entropy alloy)-Coated Copper: A Molecular Dynamics Simulation-Based Study

In this paper, the deformation behavior of Cu20Ni20Al20Co20Fe20 high-entropy alloy-coated single-crystal Cu substrate which undergoes nanoindentation has been investigated under molecular dynamic simulation with embedded-atom method potential. The dynamic structural evolutions under nanoindentation are presented using centrosymmetry parameter analysis, common neighbor analysis and radial distribution function plots. In the initial level of nanoindentation, the interface deformation is greatly confronted by the confined V-shaped growth of the distorted structure. But the sudden discrete dislocation burst account for avalanche break-down in the interface layer, which further get influenced by the evolution of multiple dislocation nodes that is significantly governed by core spreading, extended misfit dislocation generation and relative rotation. In the meanwhile, the subsequent generation of dislocation locks, complicated multiple dislocation loops, dislocation junctions and limited cross-slip in wide stacking faults (SFs) hasten the work hardening and in turn slows down the deformation progress. On the other hand, the intermediate appearance of narrow SFs and slip bands significantly reduces the work hardening rate that increases the optimum fracture strain value of the specimen. Moreover, the overall increase in dislocation density and dislocation length leads to a significant growth in dislocation sources which leads to forest hardening in the later stage.

Low dislocation density MBE process for CdTe-on-GaSb as an alternative substrate for HgCdTe growth

This work demonstrates a low dislocation density molecular beam epitaxial process (average etch pit density ∼1.4 × 105 cm−2) for the growth of CdTe buffer layers on GaSb (211)B alternative substrates for subsequent growth of HgCdTe infrared materials. This dislocation density is much lower than that for CdTe layers grown on other alternative substrates (mid-106 to low-107 cm−2 range for Si, Ge and GaAs), is well below the critical level required for fabricating high performance long-wave infrared HgCdTe detectors (5 × 105 cm−2), and is close to that achieved on lattice-matched CdZnTe substrates (mid-104 to low-105 cm−2 range). The low dislocation density is achieved by inserting a ZnTe/CdTe-based transitional buffer layer between the GaSb substrate and the CdTe buffer layer. The main purpose of this transitional buffer layer is to better accommodate the 6.1% lattice mismatch between the GaSb substrate and the CdTe epitaxial layer, which is evidenced by X-ray diffraction reciprocal space mapping. Additional benefits of this transitional buffer layer include possible blocking/filtering of misfit dislocation propagation, as well as gettering of defects and impurities. More importantly, an even lower dislocation density can be expected by increasing the thickness of the CdTe epitaxial layer and implementing a thermal annealing cycle for more efficient gettering. The results of this study indicate the great potential of GaSb as an alternative substrate for growing next generation HgCdTe infrared materials to meet the focal plane array requirements of higher device yield, lower cost and larger array format size.

A phase field crystal model simulation of morphology evolution and misfit dislocation generation in nanoheteroepitaxy

A phase field crystal (PFC) model is employed to study morphology evolution of nanoheteroepitaxy and misfit dislocation generation when applied with enhanced supercooling, lattice mismatch and substrate vicinal angle conditions. Misfit strain that rises due to lattice mismatch causes rough surfaces or misfit dislocations, deteriorates film properties, hence, efforts taken to reveal their microscopic mechanism are significant for film quality improvement. Uniform islands, instead of misfit dislocations, are developed in subcritical thickness film, serving as a way of strain relief by surface mechanism. Misfit dislocations generate when strain relief by surface mechanism is deficient in higher supercooling, multilayers of misfit dislocations dominate, but the number of layers reduces gradually when the supercooling is further enhanced. Rough surfaces like islands or cuspate pits are developed which is ascribed to lattice mismatch, multilayers of misfit dislocations generate to further enhance lattice mismatch. Layers of misfit dislocations generate at a thickening position at enhanced substrate vicinal angle, this further enhancing the angle leading to sporadic generation of misfit dislocations.

Misfit dislocation locking and rotation during gallium nitride growth on SiC/Si substrates

The effect of changing the misfit dislocation propagation direction during GaN layer growth on the AlN/SiC/Si(111) structure surface is detected. The effect is as follows. As the GaN layer growing on AlN/SiC/Si(111) reaches a certain thickness of ~300 nm, misfit dislocations initially along the layer growth axis stop and begin to move in the direction perpendicular to the growth axis. A theoretical model of AlN and GaN nucleation on the (111) SiC/Si face, explaining the effect of changing the misfit dislocation motion direction, is constructed. The effect of changing the nucleation mechanism from the island one for AlN on SiC/Si(111) to the layer one for the GaN layer on AlN/SiC/Si is experimentally detected and theoretically explained.

Impact of strain on periodic gain structures in vertical external cavity surface-emitting lasers

In this article, the impact of strain relaxation on the emission properties of InGaAs/GaAs multiple quantum wells without strain compensation was examined. Structures consisting of different numbers of quantum wells, namely 4, 8, 12 and 16, on top of distributed Bragg reflectors were grown by molecular beam epitaxy as a typical vertical external cavity surface-emitting laser (VECSEL). The relation between emission parameters in the lasing regime and strain relaxation were investigated. A two-step control of the growth rate allowed for obtaining fixed spectral detuning in all structures regardless of the number of quantum wells. The heterostructures varied in its strain and the microcavity length. The other parameters remained unchanged. In consequence, for the first time a unique set of VECSEL-like heterostructures was investigated. The strain was analyzed by reciprocal space mapping using high-resolution X-ray diffractometry. It was found that the degree of structure relaxation caused by misfit dislocation generation depends linearly on the number of quantum wells. By fitting numerical simulations to the experimental results, we have quantitatively determined the extent to which output power was suppressed by increase in non-radiative recombination arising from misfit dislocations. The non-radiative coefficients were determined. Taking output power as a criterion, we determined the optimal number of QWs to be 12 and the maximum tolerable relaxation value of 0.27 for InGaAs/GaAs VECSEL structures with uniformly distributed quantum wells in microcavity. The dependence of the monomolecular recombination coefficient on structure relaxation has been determined.

Misfit dislocations induced by lithium-ion diffusion in a thin film anode

According to the diffusion kinetics and heteroepitaxial strained layer theory, this paper presents a theoretical model to investigate the generation and distribution of misfit dislocations in a thin film anode under galvanostatic and potentiostatic operations. The results show that the nucleation and density distribution of misfit dislocations largely depend on the thickness of the diffused layer and insertion time. When the thickness is less than a certain critical value, the total strain energy in the electrode is almost insusceptible and yet reduced by misfit dislocations for that of going beyond the critical value. Under potentiostatic operation, the rise range and response speed of the dislocation density are greater and faster. A certain region immediately possesses much lower dislocation density under the electrode surface compared with the region below it. These quantitative results can provide a new perspective into relieving diffusion-induced stress by misfit dislocations with the purpose of improving the mechanical durability of lithium-ion batteries.

Heterogeneous Integration of InGaAs Nanowires on Si(111) for Si Photonics

1. Introduction In recent years, as the advancement of miniaturization of Si LSI in CMOS technology, the electrical connection inside and outside of the chip is facing technical limitations in terms of speed and miniaturization. To solve this problem, optical interconnection and Si photonics, in which various photonic devices are integrated on a Si platform, has been attracting much attention. One of their challenges is light sources, because Si is an indirect-gap semiconductor, and direct integration of highly efficient light emitters based, for instance, on InGaAs has a various problems, such as generation of misfit dislocations due to lattice mismatch between InGaAs and Si, and growth of polar materials on non-polar substrates. A small footprint of nanowires (NWs) grown by selective-area Metal-Organic Vapor-Phase Epitaxy (MOVPE) enables us to overcome these issues because it accommodates lattice mismatch. In this study, we investigated growth behavior of InGaAs NWs, which have compatible bandgap for optical communication band, on Si(111) substrates by selective-area growth. 2. Experimental Si(111) substrates partially masked with 20nm-thick SiO2 for NW growth were prepared by thermal oxidation, electron-beam lithography, and wet chemical etching. InGaAs NWs were grown by selective-area MOVPE, using trimethylgallium (TMGa), trimethylindium (TMIn), and arsine (AsH3) as source materials. To form (111)B polarity on non-polar Si(111) surfaces, special care was taken following Ref. [1]. After the removal of native oxide on Si surfaces by thermal cleaning in a hydrogen atmosphere at above 900°C, AsH3 was supplied for the replacement of outermost Si with As. Then, In order to form a high-quality interface of InGaAs and Si, InGaAs layers were grown firstly by flow-rate modulated epitaxy (FME), in which TMIn/TMGa and AsH3 was supplied alternately with hydrogen intervals. The growth temperature was 670°C. The intended composition of In in InGaAs was 47%, which had a bandgap corresponding to 1.55 μm, and had a lattice mismatch with Si by about 7.7%. 3. Results and discussion We found that the formation of InGaAs NWs critically depended on the diameter d of the NWs (or mask opening). When d was less than 200 nm, hexagonal structures surrounded by vertical {-110} facets appeared and vertical InGaAs NWs were formed in the most of the mask opening. This indicates that (111)B polarity was formed successfully on Si(111) surface and the growth direction of InGaAs was controlled into the vertical <111> direction. However, we also found no InGaAs growth took place in some openings. This is presumably due to a failure of initial nucleation process in some openings. It is noted that number of openings without growth increased as d decreased. On the other hand, when d was larger than 200nm, InGaAs in the hexagonal NW form decreased and anomalous lateral growth over the mask were observed. These results are understood as follows. When d is small, possibility of nucleation of InGaAs on Si is also small. Thus, single, or sometimes, no nuclei were formed in the opening for small d. As d becomes larger, possibility of nucleation increases, resulting in the increase of yield of NW growth. However, if d becomes too large, it is likely that multiple nuclei are formed [2]. Moreover, as the growth proceeds, those nuclei will coalesce but, because of the lattice mismatch between InGaAs and Si, the coalesced InGaAs are thought to contain threading dislocations. Finally, they are ended in laterally overgrown structures, as reported in Ref [2]. Thus, it is important to make sure that a single nucleus is formed for each opening for the growth of NWs. As also reported in Ref. [2], formation of nuclei on Si depends on In composition of InGaAs. In addition, the optimal growth procedure for the NWs on Si is different between InAs [1] and GaAs [3]. These findings suggest that optimal growth conditions, particularly at the initial stage of the growth, is composition-dependent for InGaAs, Thus, optimization of AsH3 thermal treatment and FME process is necessary to increase the yield of NW growth for optical communication band. 4. Summary We have achieved to grow InGaAs NWs vertically on Si(111) substrates with In composition around 47 %, and it was found that the nanowire facet growth changes due to influence of the nucleation and the lattice mismatch. Detailed investigation of InGaAs NWs by m-photoluminescence measurement and electrical characterization will be presented. 5.

(Invited) Anisotropic Strain Introduction into Si/Ge Hetero Structures

We show that anisotropic strain can be induced into Si/Ge hetero structures by growing them on selectively ion-implanted substrates. It is found that strain relaxation of SiGe buffer layers takes place through generation of misfit dislocations along one direction, perpendicular to the selectively ion-implanted stripe patterns. As a result, the SiGe buffer layers accommodate anisotropic (uniaxial) strain states, which are highly stable and controllable since the relaxation is based on the plastic deformation by the dislocations. On the strain controlled SiGe buffers, uniaxially strained Si/Ge channels can be grown and are highly applicable to high-mobility complementary metal oxide semiconductor (CMOS) channels.