OPTICAL IMAGING OF DISLOCATIONS IN STRAINED—LAYER SUPERLATTICES AND LATTICE—MISMATCHED EPILAYERS

1985 ◽  
Vol 56 ◽  
Author(s):  
P. L. GOURLEY ◽  
R. M. BIEFELD ◽  
L. R. DAWSON
Keyword(s):  
Optical Imaging ◽  
Critical Thickness ◽  
Optical Quality ◽  
Thin Layers ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Semiconductor Alloys ◽  
Strained Layer ◽  
Strained Layer Superlattices

AbstractWe have developed a convenient photoluminescence microimaging technique to probe misfit dislocations in epitaxially grown semiconductor alloys and multilayers. Using this technique, we have examined the microscopic optical quality of thick (~ 1 μm ) III-V semiconductor epitaxial layers, mismatched to their substrates. The layers includeseveral kinds of [100] strained-layer superlattices (GaP/GaAsxP1-x on GaP and GaAs/GaAs. P on GaAs grown by MOCVD, and GaAs/In Ga1-x As on GaAs grown by MBE) and associated alloys. For each type of superlalti e, we have studied a large number of samples corresponding to different compositions and layer thicknesses. The results show that misfit dislocations can be completely eliminated in the uppermost layers of the strained-layer superlattices if these structures have thin layers, less than the critical thickness for elastic accommodation, and sufficient numbers of interfaces to block threading dislocations.

Confinement of Threading Dislocations in Simox with a GeSi Strained Layer

1990 ◽  
Vol 198 ◽  
Author(s):  
F. Namavar ◽  
E. Cortesi ◽  
D.L. Perry ◽  
E.A. Johnson ◽  
N.M. Kalkhoran ◽  
...  
Keyword(s):  
Alloy Layer ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Epitaxial Silicon ◽  
Strained Layers ◽  
Strained Layer ◽  
Si Substrates ◽  
Plane View ◽  
Gesi Layer

ABSTRACTWe have investigated improving the crystalline quality of epitaxial silicon grown on SIMOX by confining threading dislocations in the original Si top layer using a GeSi strained layer. Epitaxial Si/GeSi/Si structures were grown by CVD on SIMOX and Si substrates with a GeSi alloy layer about 1000 − 1500 angstroms thick with Ge concentrations of about 0−20%. A Ge concentration in the alloy layer of about 5.5% or higher appears to be necessary in order to bend any of the threading dislocations from the original SIMOX top layer. For a higher Ge concentration of about 16%, most of the threading dislocations appear to be bent and confined by the GeSi layer. In addition, the GeSi strained layers grown by CVD (at about 1000°C) appear to be high quality and no misfit dislocations were observed in the regions studied by XTEM and plane view TEM.

Asymmetric Mosaic Spread During Relaxation in SiGe/ Si Strained Layer Superlattices Grown on Miscut Substrates

1995 ◽  
Vol 379 ◽  
Author(s):  
S. Nam ◽  
M. S. Goorsky
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Critical Thickness ◽  
Chemical Vapor ◽  
Misfit Dislocations ◽  
Satellite Peak ◽  
Strained Layer ◽  
Mosaic Spread ◽  
Peak Intensity ◽  
Strained Layer Superlattices

ABSTRACTThe evolution of defects in SiGe/Si strained layer superlattices (SLS)-with thickness and composition near the critical thickness -was investigated. The structures were grown on 2° miscut (001) substrates by ultrahigh vacuum chemical vapor deposition. The samples were then annealed between 700 °C and 900 °C. After annealing, the satellite peak intensity from double axis diffraction decreased and triple axis diffraction showed that this decreased intensity was due to increased mosaic structure. Interestingly, for some of the annealed samples, the (004) reciprocal space maps showed an asymmetric mosaic spread, indicating a preferential tilt. This result stems from a preferential propagation of certain types of misfit dislocations due to the substrate miscut.

Defect Reduction in GaAs Epilayers on Si Substrates Using Strained Layer Superlattices

1987 ◽  
Vol 91 ◽  
Author(s):  
N. El-Masry ◽  
N. Hamaguchi ◽  
J.C.L. Tarn ◽  
N. Karam ◽  
T.P. Humphreys ◽  
...  
Keyword(s):  
Thermal Annealing ◽  
Rapid Thermal Annealing ◽  
Buffer Layers ◽  
Threading Dislocations ◽  
Defect Reduction ◽  
Strained Layer ◽  
Si Substrates ◽  
Density Of Dislocations ◽  
Strained Layer Superlattice ◽  
Strained Layer Superlattices

ABSTRACTInxGa11-xAs-GaAsl-yPy strained layer superlattice buffer layers have been used to reduce threading dislocations in GaAs grown on Si substrates. However, for an initially high density of dislocations, the strained layer superlattice is not an effective filtering system. Consequently, the emergence of dislocations from the SLS propagate upwards into the GaAs epilayer. However, by employing thermal annealing or rapid thermal annealing, the number of dislocation impinging on the SLS can be significantly reduced. Indeed, this treatment greatly enhances the efficiency and usefulness of the SLS in reducing the number of threading dislocations.

Threading Dislocation Density Reduction in GaN/Sapphire Heterostructures.

1999 ◽  
Vol 595 ◽  
Author(s):  
A. Kvit ◽  
A. K. Sharma ◽  
J. Narayan
Keyword(s):  
Basal Plane ◽  
Stacking Faults ◽  
High Density ◽  
Thin Layers ◽  
Interfacial Region ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Plan View ◽  
Partial Dislocations

AbstractLarge lattice mismatch between GaN and α-Al2O3 (15%) leads to the possibility of high threading dislocation densities in the nitride layers grown on sapphire. This investigation focused on defect reduction in GaN epitaxial thin layer was investigated as a function of processing variables. The microstructure changes from threading dislocations normal to the basal plane to stacking faults in the basal plane. The plan-view TEM and the corresponding selected-area diffraction patterns show that the film is single crystal and is aligned with a fixed epitaxial orientation to the substrate. The epitaxial relationship was found to be (0001)GaN∥(0001)Sap and [01-10]GaN∥[-12-10]Sap. This is equivalent to a 30° rotation in the basal (0001) plane. The film is found to contain a high density of stacking faults with average spacing 15 nm terminated by partial dislocations. The density of partial dislocations was estimated from plan-view TEM image to be 7×109 cm−2. The cross-section image of GaN film shows the density of stacking faults is highest in the vicinity of the interface and decreases markedly near the top of the layer. Inverted domain boundaries, which are almost perpendicular to the film surface, are also visible. The concentration of threading dislocation is relatively low (∼;2×108 cm−2), compared to misfit dislocations. The average distance between misfit dislocations was found to be 22 Å. Contrast modulations due to the strain near misfit dislocations are seen in high-resolution cross-sectional TCM micrograph of GaN/α-Al2O3 interface. This interface is sharp and does not contain any transitional layer. The interfacial region has a high density of Shockley and Frank partial dislocations. Mechanism of accommodation of tensile, sequence and tilt disorder through partial dislocation generation is discussed. In order to achieve low concentration of threading dislocations we need to establish favorable conditions for some stacking disorder in thin layers above the film-substrate interface region.

scholarly journals The Structure of GaAs/Si(211) Heteroepitaxial Layers

1987 ◽  
Vol 91 ◽  
Author(s):  
Zuzanna Liliental-Weber ◽  
E.R. Weber ◽  
J. Washburn ◽  
T.Y. Liu ◽  
H. Kroemer
Keyword(s):  
Buffer Layer ◽  
Surface Preparation ◽  
Gaas Layer ◽  
Misfit Dislocations ◽  
Strained Layer ◽  
Si Substrates ◽  
Density Of Dislocations ◽  
Gaas Buffer Layer ◽  
Graded Layers ◽  
Strained Layer Superlattices

ABSTRACTGallium arsenide films grown on (211)Si by molecular-beam epitaxy have been investigated using transmission electron microscopy. The main defects observed in the alloy were of misfit dislocations, stacking faults, and microtwin lamellas. Silicon surface preparation was found to play an important role on the density of defects formed at the Si/GaAs interface.Two different types of strained-layer superlattices, InGaAs/InGaP and InGaAs/GaAs, were applied either directly to the Si substrate, to a graded layer (GaP-InGaP), or to a GaAs buffer layer to stop the defect propagation into the GaAs films. Applying InGaAs/GaAs instead of InGaAs/InGaP was found to be more effective in blocking defect propagation. In all cases of strained-layer superlattices investigated, dislocation propagation was stopped primarily at the top interface between the superlattice package and GaAs. Graded layers and unstrained AlGaAs/GaAs superlattices did not significantly block dislocations propagating from the interface with Si. Growing of a 50 nm GaAs buffer layer at 505°C followed by 10 strained-layer superlattices of InGaAs/GaAs (5 nm each) resulted in the lowest dislocation density in the GaAs layer (∼;5×l07/cm2) among the structures investigated. This value is comparable to the recently reported density of dislocations in the GaAs layers grown on (100)Si substrates [8]. Applying three sets of the same strained layersdecreased the density of dislocations an additional ∼2/3 times.

Equilibrium Analysis of Lattice-Mismatched Nanowire Heterostructures

2002 ◽  
Vol 737 ◽  
Author(s):  
E. Ertekin ◽  
P.A. Greaney ◽  
T. D. Sands ◽  
D. C. Chrzan
Keyword(s):  
Simple Model ◽  
Misfit Dislocation ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Equilibrium Analysis ◽  
Misfit Dislocations ◽  
Model Based ◽  
Large Lattice ◽  
Large Lattice Mismatch

ABSTRACTThe quality of lattice-mismatched semiconductor heterojunctions is often limited by the presence of misfit dislocations. Nanowire geometries offer the promise of creating highly mismatched, yet dislocation free heterojunctions. A simple model, based upon the critical thickness model of Matthews and Blakeslee for misfit dislocation formation in planar heterostructures, illustrates that there exists a critical nanowire radius for which a coherent heterostructured nanowire system is unstable with respect to the formation of misfit dislocations. The model indicates that within the nanowire geometry, it should be possible to create perfect heterojunctions with large lattice-mismatch.

Optical Investigation of Critical Thickness and Interface Fluctuation in CdSe/ZnSe Strained Layer Superlattices Grown on InP

2000 ◽  
Vol 39 (Part 1, No. 5A) ◽  
pp. 2541-2545 ◽  
Author(s):  
Yoichi Nabetani ◽  
Isao Ishibe ◽  
Kazuki Sugiyama ◽  
Takamasa Kato ◽  
Takashi Matsumoto
Keyword(s):  
Critical Thickness ◽  
Optical Investigation ◽  
Strained Layer ◽  
Strained Layer Superlattices ◽  
Interface Fluctuation

Critical thickness of common-anion II–VI strained layer superlattices (SLSs)

1992 ◽  
Vol 117 (1-4) ◽  
pp. 492-496 ◽  
Author(s):  
P.J. Parbrook ◽  
B. Henderson ◽  
K.P. O'Donnell ◽  
P.J. Wright ◽  
B. Cockayne
Keyword(s):  
Critical Thickness ◽  
Strained Layer ◽  
Strained Layer Superlattices ◽  
Common Anion

Misfit dislocations between boron-doped homoepitaxial films and diamond substrates studied by X-ray diffraction topography

2018 ◽  
Vol 51 (6) ◽  
pp. 1684-1690 ◽  
Author(s):  
Marina González-Mañas ◽  
Beatriz Vallejo
Keyword(s):  
Critical Thickness ◽  
Lattice Mismatch ◽  
Lattice Parameter ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Boron Doped Diamond ◽  
X Ray ◽  
Boron Doped ◽  
Slip Planes ◽  
Half Loop

Boron-doped diamond epilayers grown over diamond substrates have a different lattice parameter from the undoped diamond substrate, which introduces a lattice mismatch between substrates and epilayers. This can generate misfit dislocations at the interface when the epilayer reaches a certain critical thickness. For a boron concentration of about 1 × 1020 atoms cm−3, the calculated lattice mismatch is about 1.3 × 10−4 and the critical thickness is of the order of 0.2 µm. In the epilayers studied, grown over high-pressure high-temperature 1b (001) substrates, the lattice mismatch and the epilayer thickness are 1.3 × 10−4, 30 µm and 6.5 × 10−4, 4 µm. The epitaxial strain has been relaxed by the generation of two orthogonal misfit dislocation systems. These are edge dislocations parallel to the [100] and [010] directions with a Burgers vector making an angle of 45° with the (001) interface. Their lengths are 40–60 µm and their lineal densities 200–240 cm−1. They are heterogeneously nucleated, propagated in the form of half-loops along the slip planes (011) and (101), respectively, and related mainly to 〈111〉 threading dislocations emerging from octahedral growth sectors. Another kind of half-loop originates from the substrate growth sector boundaries. Limited X-ray topography has been demonstrated to be a very useful tool to discriminate between substrate and epilayer defects when their lattice mismatch is not sufficient to separate such defects in conventional Lang topography. X-ray section topography has confirmed the presence of [001] dislocations in the epilayers and the misfit half-loops related to threading dislocations propagating from the interface.

A Refined Model For Threading Dislocation Filtering In InxGa1−xAs/GaSAs Epitaxial Layers

1996 ◽  
Vol 442 ◽  
Author(s):  
G. Macpherson ◽  
P. J. Goodhew
Keyword(s):  
Large Scale ◽  
Critical Thickness ◽  
Thin Layers ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Refined Model ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dislocation Densities ◽  
High Level

AbstractA model is presented for the filtering of threading dislocations in InxGa1−xAs/GaAs epitaxial single layers by accurate control of the layer thickness. The model developed differs from previous models since the InxGa1−xAs growth is restricted to less than ten times the Matthews and Blakeslee critical thickness (hc) where the asymmetry in the [110] and [110] dislocation densities is the greatest. Beyond this thickness it is shown that the removal or annihilation of threading dislocations (TDs) in the epilayer is more than offset by the introduction of new TDs from spiral and Frank-Read type sources. Results from strain sensitive etching with CrO3 aqueous solutions show that the TD density can be reduced by up to a factor of ten below that found in the substrate. Atomic force microscopy shows that these thin layers maintain a high level of surface quality with an absence of striations. Evidence is also shown that this type of defect etching is suitable for revealing large scale dislocation blocking in samples that have been grown significantly beyond 10hc.

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