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.

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,

Strain Relaxation in GaAs on Si by Two Groups of Misfit Dislocations

1995 ◽  
Vol 399 ◽  
Author(s):  
M. Tamura ◽  
T. Saitoh ◽  
T. Yodo
Keyword(s):  
Strain Relaxation ◽  
Lattice Misfit ◽  
Misfit Dislocations ◽  
Cross Sectional ◽  
Plan View ◽  
Partial Dislocations ◽  
Group I ◽  
Transmission Electron ◽  
Before And After ◽  
Gaas Films

ABSTRACTHigh-resolution cross-sectional and conventional plan-view transmission electron microscope observations have been carried out for molecular beam epitaxially grown GaAs films on vicinal Si (001) as a function of film thicknesses and observation directions between two orthogonal <110> directions before and after annealing. Two groups of misfit dislocations are characterized by analyzing whether their extra half planes exist in the film and the substrate side. The group I misfit dislocations due to a stress caused by a lattice misfit between GaAs and Si consist of partial and, 60° and 90° complete dislocations in an as-grown state. After annealing partial dislocations almost disappear and 90° perfect dislocations are predominantly observed. The group II misfit dislocations due to a thermal-expansion misfit-induced stress are all of the 60° type complete dislocations, independent of film thickness and annealing.

scholarly journals In-Situ TEM Studies of the Interaction Between Dislocations in SiGe Heterostructures

1999 ◽  
Vol 5 (S2) ◽  
pp. 728-729
Author(s):  
E.A. Stach ◽  
R. Hull ◽  
R.M. Tromp ◽  
F.M. Ross ◽  
M.C. Reuter ◽  
...  
Keyword(s):  
Strain Relaxation ◽  
Chemical Vapor ◽  
Dislocation Nucleation ◽  
In Situ Tem ◽  
Misfit Dislocations ◽  
Heteroepitaxial Growth ◽  
Metastable Structures ◽  
Theoretical Predictions ◽  
Gap States

The rate of heteroepitaxial strain relaxation via misfit dislocation introduction is strongly limited by the kinetics of dislocation nucleation, propagation and interaction. Here we describe real-time observations of the interaction between moving threading dislocations and pre-existing interfacial misfit dislocations using in-situ transmission electron microscopy. This was accomplished both during in-situ observations of the heteroepitaxial growth process using a modified ultrahigh vacuum TEM (UHV-TEM) equipped with chemical vapor deposition capabilities, as well as during in-situ anneals of metastable structures grown by molecular beam epitaxy.In Figure 1, we present our UHV-TEM observations of the epilayer thicknesses and compositions at which dislocation interactions result in blocking of the propagating threading segment, and compare these with the theoretical predictions of Freund and those of Schwarz and Tersoff. Our results show that dislocation blocking can significantly affect the overall rate of strain relaxation in these structures. This is important, as blocked threading segments introduce undesired band gap states into electronic devices and can act as easy diffusion paths for impurities and dopants.

Kinetic Barriers to Strain Relaxation in GexSi1-x/Si Epitaxy

1989 ◽  
Vol 160 ◽  
Author(s):  
R. Hull ◽  
J.C. Bean
Keyword(s):  
Relaxation Process ◽  
Misfit Dislocation ◽  
Strain Relaxation ◽  
Dislocation Nucleation ◽  
Transmission Electron ◽  
Structure Geometry ◽  
Si Epitaxy ◽  
Annealing Experiments ◽  
Kinetic Barriers

AbstractWe discuss the kinetic barriers to misfit dislocation nucleation, propagation and interaction in lattice-mismatched GexSi1-x/Si epitaxy. Experimental real-time observations of the strain relaxation process via in-situ annealing experiments in a transmission electron microscope enable each of these processes to be separately studied. Quantitative parameters defining misfit dislocation processes may be derived; these are found to be highly dependent upon the structure geometry. The approximations involved in extending these measurements to a description of the relaxation process during growth are described in detail.

Strain Relaxation Via Interface Nucleation of Misfit Dislocations in Intermixing Layers

1992 ◽  
Vol 263 ◽  
Author(s):  
Hyo-Hoon Park ◽  
Jung Kee Lee ◽  
El-Hang Lee ◽  
Jeong Yong Lee ◽  
Soon-Ku Hong
Keyword(s):  
Electron Microscopy ◽  
Homogeneous Nucleation ◽  
Critical Thickness ◽  
Strain Relaxation ◽  
Relaxation Mechanism ◽  
Semiconductor Heterostructures ◽  
Misfit Dislocations ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Lattice Matched

ABSTRACTThe strain relaxation mechanism via the homogeneous nucleation of misfit dislocations from interface during interdiffusion in lattice-matched semiconductor heterostructures has been investigated. Transmission electron microscopy studies in intermixed GaInAsP/InP heterostructures revealed that the critical interdiffusion depth for the nucleation of 90° 1/6<112> partial dislocations from a tensile interface is much shallower than that of 60° 1/2<110> perfect dislocations from a compressive interface. A critical thickness model for the interface nucleation of these dislocations is developed as a modification of the classical surface nucleation'model.

Experimental and Theoretical Analysis of Strain Relaxation in GexSi1-x/Si(100) Heteroepitaxy

1989 ◽  
Vol 148 ◽  
Author(s):  
R. Hull ◽  
J.C. Bean
Keyword(s):  
Misfit Dislocation ◽  
Strain Relaxation ◽  
Dislocation Nucleation ◽  
Fundamental Parameters ◽  
Interaction Processes ◽  
Transmission Electron ◽  
Wide Range ◽  
Relaxation Measurements ◽  
Good Agreement

ABSTRACTBy analyzing in-situ strain relaxation measurements of GexSi1-x/Si(100) epitaxy in a Transmission Electron Microscope, we are able to quantify the fundamental parameters which describe strain energy relaxation via misfit dislocation introduction. Quantitative descriptions of misfit dislocation nucleation, propagation and interaction processes are derived. The numerical parameters obtained from these experiments are then incorporated into a predictive theoretical model of strain relaxation whichrelies only upon experimentally measured quantities. Good agreement between experiment and theory is obtained over a wide range of data.

In situ TEM measurements of the electrical properties of interface dislocations

1992 ◽  
Vol 50 (2) ◽  
pp. 1338-1339
Author(s):  
F. M. Ross ◽  
R. Hull ◽  
D. Bahnck ◽  
J. C. Bean ◽  
L. J. Peticolas ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Electronic Device ◽  
In Situ Tem ◽  
Device Performance ◽  
Misfit Dislocations ◽  
Electrical Characteristics ◽  
Strained Layer ◽  
Transmission Electron ◽  
Interfacial Dislocations

We describe an investigation of the electrical properties of interfacial dislocations in strained layer heterostructures. We have been measuring both the structural and electrical characteristics of strained layer p-n junction diodes simultaneously in a transmission electron microscope, enabling us to correlate changes in the electrical characteristics of a device with the formation of dislocations.The presence of dislocations within an electronic device is known to degrade the device performance. This degradation is of increasing significance in the design and processing of novel strained layer devices which may require layer thicknesses above the critical thickness (hc), where it is energetically favourable for the layers to relax by the formation of misfit dislocations at the strained interfaces. In order to quantify how device performance is affected when relaxation occurs we have therefore been investigating the electrical properties of dislocations at the p-n junction in Si/GeSi diodes.

Transmission electron microscopy of misfit dislocation and strain relaxation in lattice mismatched III-V heterostructures versus substrate surface treatment

2011 ◽  
Vol 1324 ◽  
Author(s):  
Y. Wang ◽  
P. Ruterana ◽  
L. Desplanque ◽  
S. El Kazzi ◽  
X. Wallart
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Surface Treatment ◽  
Substrate Surface ◽  
Strain Relaxation ◽  
Dislocation Core ◽  
Misfit Dislocations ◽  
Heteroepitaxial Growth ◽  
Transmission Electron ◽  
Growth Initiation

ABSTRACTHigh resolution transmission electron microscopy in combination with geometric phase analysis is used to investigate the interface misfit dislocations, strain relaxation, and dislocation core behavior versus the surface treatment of the GaAs for the heteroepitaxial growth of GaSb. It is pointed out that Sb-rich growth initiation promotes the formation of a high quality network of Lomer misfit dislocations that are more efficient for strain relaxation.

Transition From Inclined to In-Plane 60° Misfit Dislocations in a Diffuse Interface

1993 ◽  
Vol 319 ◽  
Author(s):  
X. J. Ning ◽  
P. Pirouz
Keyword(s):  
Strain Relaxation ◽  
Classical Model ◽  
Diffuse Interface ◽  
Misfit Dislocations ◽  
Dislocation Loops ◽  
Boron Diffusion ◽  
Plan View ◽  
Transmission Electron ◽  
Mechanisms Of Formation ◽  
Film Substrate

AbstractDespite tremendous activity during the last few decades in the study of strain relaxation in thin films grown on substrates of a dissimilar material, there are still a number of problems which are unresolved. One of these is the nature of misfit dislocations forming at the film/substrate interface: depending on the misfit, the dislocations constituting the interfacial network have predominantly either in-plane or inclined Burgers vectors. While, the mechanisms of formation of misfit dislocations with inclined Burgers vectors are reasonably well understood, this is not the case for in-plane misfit dislocations whose formation mechanism is still controversial. In this paper, misfit dislocations generated to relax the strains caused by diffusion of boron into silicon have been investigated by plan-view and crosssectional transmission electron microscopy. The study of different stages of boron diffusion shows that, as in the classical model of Matthews, dislocation loops are initially generated at the epilayer surface. Subsequently the threading segments expand laterally and lay down a segment of misfit dislocation at the diffuse interface. The Burgers vector of the dislocation loop is inclined with respect to the interface and thus the initial misfit dislocations are not very efficient. However, as the diffusion proceeds, non-parallel dislocations interact and give rise to product segments that have parallel Burgers vectors. Based on the observations, a model is presented to elucidate the details of these interactions and the formation of more efficient misfit dislocations from the less-efficient inclined ones.

Mechanisms of misfit strain relaxation in epitaxially grown BLT (Bi4-xLaxTi3O12, x = 0.75) thin films

2003 ◽  
Vol 779 ◽  
Author(s):  
Hyung Seok Kim ◽  
Sang Ho Oh ◽  
Ju Hyung Suh ◽  
Chan Gyung Park
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Strain Relaxation ◽  
Lattice Misfit ◽  
Misfit Strain ◽  
Misfit Dislocations ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
20 Nm

AbstractMechanisms of misfit strain relaxation in epitaxially grown Bi4-xLaxTi3O12 (BLT) thin films deposited on SrTiO3 (STO) and LaAlO3 (LAO) substrates have been investigated by means of transmission electron microscopy (TEM). The misfit strain of 20 nm thick BLT films grown on STO substrate was relaxed by forming misfit dislocations at the interface. However, cracks were observed in 100 nm thick BLT films grown on the same STO. It was confirmed that cracks were formed because of high misfit strain accumulated with increasing the thickness of BLT, that was not sufficiently relaxed by misfit dislocations. In the case of the BLT film grown on LAO substrate, the magnitude of lattice misfit between BLT and LAO was very small (~1/10) in comparison with the case of the BLT grown on STO. The relatively small misfit strain formed in layered structure of the BLT films on LAO, therefore, was easily relaxed by distorting the film, rather than forming misfit dislocations or cracks, resulting in misorientation regions in the BLT film.

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