Interfacial Microstructures in InxGa1-xAs/GaAs Strained Layer Structures

1989 ◽  
Vol 148 ◽  
Author(s):  
J. Y. Yao ◽  
T. G. Andersson ◽  
G. L. Dunlop
Keyword(s):  
Molecular Beam ◽  
Imaging Technique ◽  
Three Dimensional ◽  
Strained Layer ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Layer Structures ◽  
Structural Imperfections ◽  
2D To 3D

ABSTRACTThe interfacial microstructures of lattice strained InxGal-xAs/GaAs multiple layer structures, that were grown by molecular beam epitaxy (MBE) on GaAs (100) substrates, have been investigated and characterised by transmission electron microscopy (TEM). A g3ii weak beam imaging technique has been used to study structural imperfections at the heterointerfaces. The morphology of rough heterointerfaces, which resulted from the growth of the InxGal-xAs layers (strained layer) either in a two dimensional (2D) or in a three dimensional (3D) growth mode via island formation, was imaged using this technique. A transition from 2D to 3D growth was found to occur at a certain critical layer thickness which decreased with increasing indium fraction. In thicker layers, dislocation complexes, which may have been caused bythe formation of islands, were also observed. These complexes were primarily composed ofstacking faults bounded by partial dislocations.

A Weak Beam Imaging Technique for the Characterization of Interfacial Roughness in (InGa)As/GaAs Strained Layer Structures

1989 ◽  
Vol 159 ◽  
Author(s):  
J. Y. Yao ◽  
T. G. Andersson ◽  
G. L. Dunlop
Keyword(s):  
Imaging Technique ◽  
Interfacial Roughness ◽  
Strained Layers ◽  
Strained Layer ◽  
Weak Beam ◽  
Kinematic Theory ◽  
Transmission Electron ◽  
Layer Structures ◽  
Made In

ABSTRACTA transmission electron microscope weak beam imaging technique has been developed for the characterization of interfacial roughness in lattice strained (InGa)As/GaAs multiple layered structures. In this technique, the heterointerfaces of (100) type strained layers are imaged in an inclined projection with a g311 diffracted reflection at off-Bragg conditions which gives an enhanced contrast from variations in strained layer thickness. A calculation based on the kinematic theory of contrast was made in order to gain a better understanding of the contrast. The calculation suggests that the observed contrast is due to monolayer scale variations in thickness of the strained layers.

Characterization of Al/GaAs Schottky barriers with thin Si interfacial layers

1993 ◽  
Vol 51 ◽  
pp. 800-801
Author(s):  
M.W. Bench ◽  
T.J. Miller ◽  
M.I. Nathan ◽  
C.B. Carter
Keyword(s):  
Molecular Beam Epitaxy ◽  
Barrier Height ◽  
Molecular Beam ◽  
Schottky Diodes ◽  
Growth Conditions ◽  
High Energy ◽  
Exact Nature ◽  
Interfacial Layers ◽  
Transmission Electron ◽  
Layer Structures

It has been shown in previous reports that barrier height variations can be achieved in GaAs Schottky diodes grown using molecular beam epitaxy by utilizing a thin epitaxial Si layer (a few monolayers) between the GaAs and the Al contact. The effective barrier height was found to be dependent on the thickness and growth conditions of the Si layer. However, there has remained a question as to the exact nature of the interfacial Si layer. In the present investigation, samples with different Si layer thicknesses (no Si, 6 Å Si, and 20 Å Si, as determined in situ during growth using reflection high energy electron diffraction (RHEED)) were characterized using transmission electron microscopy (TEM) to determine the nature of the Si layers. In the present study, it was also found that the presence of the interfacial Si layers affected the growth orientation and morphology of the Al layers.The layer structures investigated were grown using molecular beam epitaxy in a system described elsewhere.

Dynamical Study of Dislocations and 4H → 3C Transformation Induced by Stress in (11-20) 4H-SiC

2005 ◽  
Vol 483-485 ◽  
pp. 299-302 ◽  
Author(s):  
Hosni Idrissi ◽  
Maryse Lancin ◽  
Joel Douin ◽  
G. Regula ◽  
Bernard Pichaud
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chemical Etching ◽  
Stacking Faults ◽  
Sample Surface ◽  
Cubic Phase ◽  
Dynamical Study ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Transmission Electron

4H-SiC samples were bent in compression mode at temperature ranging from 400°C to 700°C. The introduced-defects were identified by Weak Beam (WB) and High Resolution Transmission Electron Microscopy (HRTEM) techniques. They consist of double stacking faults bound by 30° Si(g) partial dislocations whose glide locally transforms the material in its cubic phase. The velocity of partial dislocations was measured after chemical etching of the sample surface. The formation and the expansion of the double stacking faults are discussed.

New Relaxation Mechanism in Short Period Si/Ge Strained-Layer Superlattices

1990 ◽  
Vol 183 ◽  
Author(s):  
Werner Wegscheider ◽  
Karl Eberl ◽  
Gerhard Abstreiter ◽  
Hans Cerva ◽  
Helmut Oppolzer
Keyword(s):  
Activation Barrier ◽  
Relaxation Mechanism ◽  
Layer Growth ◽  
Lattice Imaging ◽  
Strained Layer ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Short Period ◽  
Strained Layer Superlattices ◽  
First Time

AbstractHigh quality Si/Ge strained-layer superlattices composed of a sequence of alternating 3 monolayers pure Si and 9 monolayers pure Ge have been grown by molecular beam epitaxy at 310°C on Ge(001) substrates. In order to investigate the transition from coherent to incoherent growth in these tensily strained structures a set of samples with varying number of superlattice periods has been studied by transmission electron microscopy. It is found that superlattices as thick as 33 nm at least show perfect and defect-free layer growth whereas for thicker superlattices strain accommodation occurs. For this strained heteroepitaxial system we observed, to our knowledge, for the first time the formation of microtwins as the only relaxation mechanism. High-resolution lattice imaging reveals that the twin lamellae result from successive glide of 90° (a/6)<112> Shockley partial dislocations on adjacent {111} planes from the surface towards the bulk. The activation barrier which has to be overcome in the case of 90° partial dislocations is compared with the energies required for the nucleation of 60° perfect and 30° partial misfit dislocation half-loops.

Mbe Growth of Strained-Layer InSb/InAlSb Structures

1990 ◽  
Vol 198 ◽  
Author(s):  
C.R. Whitehouse ◽  
C.F. Mcconville ◽  
G.M. Williams ◽  
A.G. Cullis ◽  
S.J. Barnett ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Critical Thickness ◽  
Multiple Quantum ◽  
Material System ◽  
X Ray Diffraction ◽  
Mbe Growth ◽  
X Ray ◽  
Strained Layer ◽  
Transmission Electron ◽  
Layer Structures

ABSTRACTThe MBE growth and related materials characterisation of InSb/InAlSb strained-layer structures is described. Band-gap considerations and critical thickness calculations are presented and indicate that this material system should offer considerable device potential. Detailed structural studies, performed using both transmission electron microscopy and X-ray diffraction, confirm the growth of high quality multiple quantum-wells, and 2K photoluminescence has shown corresponding energy upshifted transitions.

The Structure of Dislocations in GaN Grown by MBE as a Function of the Gallium to Nitrogen Ratio

2003 ◽  
Vol 798 ◽  
Author(s):  
Marcus Q. Baines ◽  
David Cherns ◽  
Sergei V. Novikov ◽  
Michael J. Manfra ◽  
C. Thomas Foxon
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam ◽  
Fundamental Property ◽  
Growth Surface ◽  
Force Microscopy ◽  
The Core ◽  
Weak Beam ◽  
Atomic Force ◽  
Transmission Electron ◽  
Nitrogen Ratio

ABSTRACTTransmission electron microscopy (TEM) and atomic force microscopy (AFM) have been used to analyse the core structure of dislocations in GaN grown by molecular beam epitaxy (MBE) as a function of the gallium to nitrogen ratio. Ga-rich samples had a much smoother morphology; TEM observations showed that amorphous deposits decorated some dislocations and occasional surface pits, but weak beam and end-on imaging suggested that, away from the growth surface, dislocations of all types had closed core structures, in contrast to previous observations (Hsu et al, Appl. Phys. Lett. 78, 3980 (2001), Baines et al, Mat. Res. Soc. Symp. Proc. 743, L2.5 (2003)). Ga-poor samples were found to have much rougher surfaces; dislocations were often at the centers of deep surface pits but were observed to be undecorated and to have closed core structures. It is concluded that in growth under Ga-rich conditions, decoration of dislocation cores depends on the accumulation of Ga at surface pits, rather than being a fundamental property of dislocation formation.

Identification of partial dislocations and faults in cubic Al3Ti

1994 ◽  
Vol 9 (3) ◽  
pp. 553-562 ◽  
Author(s):  
S. Zhang ◽  
W.W. Milligan ◽  
D.E. Mikkola
Keyword(s):  
Computer Simulation ◽  
Room Temperature ◽  
Superlattice Reflection ◽  
Bright Field ◽  
Fringe Contrast ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Ti Alloys ◽  
Transmission Electron ◽  
Imaging Conditions

Dislocation dissociations in Al3Ti alloys modified with Mn to stabilize the L12 cubic structure have been studied with transmission electron microscopy and computer simulation of images. Dissociations of a〈110〉 superdislocations into pairs of a/2〈110〉 partials bounding APB's were observed at all temperatures from room temperature to 700 °C. Asymmetrical image contrast, in which one of the a/2〈110〉 partials gives a much more intense image than the other, was observed at small separations of the partials. Although some investigators have taken such asymmetry to suggest SISF-type dissociations in similar alloys, the current work demonstrates that the asymmetry is fully consistent with APB-type dissociation. Further, the degree of image asymmetry decreases as the spacing of the partials increases. It is concluded that identification of the partial dislocations with “near-invisibility criteria” for fractional values of g · b is unreliable, and that computer simulation of images is useful for identification of the partials. However, as expected, the ability to distinguish simulated bright-field images of APB- and SISF-type dissociations also becomes difficult as the separation of the partials becomes very small. Under these conditions, both weak-beam imaging and simulations are necessary to identify the dissociations. Weak-beam simulations have shown that fringe contrast must be present under certain imaging conditions for SISF dissociations, and this contrast has never been observed in this study or in previously published studies of dissociated single superdislocations in cubic Al3Ti alloys. Finally, APB contrast formed with superlattice reflection imaging has been observed between partials on both {111} and {100} after deformation at 700 °C.

Analysis of Weak-Beam Contrast from SESF/SISF Fault Pairs Associated with ½ <112] Superdislocations in TiAl

1998 ◽  
Vol 552 ◽  
Author(s):  
Mukul Kumar ◽  
S. Sriram ◽  
Adam J. Schwartz ◽  
Vijay K. Vasudevan
Keyword(s):  
Stacking Faults ◽  
Antiphase Boundary ◽  
Stacking Fault ◽  
Intermetallic Alloy ◽  
Diffraction Contrast ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Beam Transmission ◽  
Simulated Images

ABSTRACTThe diffraction contrast from dissociated ½<112] superdislocations in γ-TiAl intermetallic alloy cannot always be analyzed using conventional rules of diffraction contrast. In particular, the configuration involving three similar Shockley partials on adjacent planes has often been ruled out due to the absence of fringes indicating the presence of stacking faults. In order to determine the dissociated configuration, weak-beam transmission electron microscope observations of edge-oriented ½<112] superdislocations have been correlated with computer simulated images. Dissociation of these superdislocations into three similar ⅙<112] partial dislocations bounding a superlattice extrinsic and intrinsic stacking fault pair has been consequently determined from these analyses. It has been found that diffraction contrast alone cannot distinguish between the various configurations that lead to the formation of the fault pair, but the formation of an antiphase boundary or complex stacking fault linked dissociation or locking by stair rod dislocations can be ruled out.

Defects in MBE-grown In AsXSb1-X strained layer superlattices

1991 ◽  
Vol 49 ◽  
pp. 852-853
Author(s):  
S. Chadda ◽  
A. K. Datye ◽  
L. R. Dawson
Keyword(s):  
Band Gap ◽  
Cross Section ◽  
Infrared Detectors ◽  
Molecular Beam ◽  
Research Groups ◽  
Active Device ◽  
Strained Layer ◽  
Transmission Electron ◽  
Strained Layer Superlattices ◽  
P Type

III-V alloy devices are being considered for applications as infrared detectors, by several research groups due to processing advantages over II-VI alloy devices. InAs0.4Sb0.6 has the lowest band gap at 77 K among all III-V compounds, which corresponds to a cut off wavelength of 9 μm. The use of strained layer superlattices (SLS) was first proposed by Osbourn for lowering the band gap and achieving absorption at wavelengths greater than 12 μm at 77 K. A schematic diagram of the device is shown in figure 1. It was grown by Molecular Beam Epitaxy (MBE) at 425 °C and it consists of a p-n junction embedded in a InAs0.15Sb0.85/InSb SLS with layers of equal (110 Å) thickness. The n and p type dopants were S (PbS) and Be respectively. The active device SLS was grown on a composition graded strain relief buffer on the (100) face of an InSb substrate. The samples were sliced, thinned, polished, dimpled and ion milled for making cross-section Transmission Electron Microscope (TEM) samples.

Dislocations in shock-loaded titanium diboride

1988 ◽  
Vol 3 (4) ◽  
pp. 761-763 ◽  
Author(s):  
D. M. Vanderwalker ◽  
W. J. Croft
Keyword(s):  
Shock Wave ◽  
Point Defects ◽  
Titanium Diboride ◽  
Basal Slip ◽  
Stacking Fault ◽  
High Concentration ◽  
Weak Beam ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Annealing Experiments

The structure of shock-loaded polycrystalline titanium diboride was examined with transmission electron microscopy. The shock wave from ballistic impact produces prismatic and basal slip in grains favorably oriented with respect to the shock wave. It can be deduced from annealing experiments with the formation of stacking fault hexagons that there is a high concentration of point defects in deformed regions from the motion of dislocation jogs. Weak-beam microscopy shows that the dislocations in TiB2 are dissociated into partial dislocations. The stacking fault energy measured from a screw dislocation in the basal plane was found to be 120 mJ/m2. Widely dissociated dislocations in the shocked sample suggest that residual stresses are present in some regions.

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