The Stability of Si-Si1-xGex Strained Layer Heterostructures.

1988 ◽  
Vol 130 ◽  
Author(s):  
D. C. Houghton ◽  
J-M. Baribeau ◽  
K. Song ◽  
D. D. Perovic
Keyword(s):  
Interference Microscopy ◽  
Layer System ◽  
Strained Layers ◽  
Strained Layer ◽  
Transmission Electron ◽  
Metastable Structures ◽  
Abrupt Changes ◽  
The Stability ◽  
Strained Layer Superlattices ◽  
Stability Limits

AbstractThe structural stability of strained layer superlattices (SLS's) is addressed using an equilibrium model and then compared to the stability of single strained layers. Relaxation mechanisms are described for various superlattice geometries. The application of a critical thickness/strain criterion to define stability limits was found to be very useful in predicting the detailed relaxation process. The competition between relaxation by misfit accommodation at the base of the SLS and at individual strained interfaces is considered for the initial condition of full coherency and after partial relaxation. Experimental data for the Si-Ge strained layer system are presented; as-grown by MBE and after annealing in the temperature range 500°C – 900°C. The extent of relaxation and the detailed dislocation structure within the SLS's were determined by X-ray rocking curve analysis, Nomarski interference microscopy and transmission electron microscopy. The abrupt changes in relaxation behaviour indicate that rigid boundaries between stable and metastable structures do exist, as predicted by the equilibrium models.

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.

Rapid Thermal Processing for Strained-Layer Semiconductor Devices

1993 ◽  
Vol 303 ◽  
Author(s):  
John C. Zolper ◽  
David R. Myers
Keyword(s):  
Band Structure ◽  
Semiconductor Lasers ◽  
Thermal Processing ◽  
Rapid Thermal Processing ◽  
Strained Layer ◽  
Layer Structures ◽  
Thermodynamic Limits ◽  
The Stability ◽  
Mismatched Heteroepitaxy ◽  
Strained Layer Superlattices

ABSTRACTStrained-layer semiconductors have revolutionized modern heterostructure devices by exploiting the modification of semiconductor band structure associated with the coherent strain of lattice-mismatched heteroepitaxy. The modified band structure improves transport of holes in heterostructures and enhances the operation of semiconductor lasers. Strainedlayer epitaxy also can create materials whose band gaps match wavelengths (e. g. 1.06 μm and 1.32 μm) not attainable in ternary epitaxial systems lattice matched to binary substrates. Other benefits arise from metallurgical effects of modulated strain fields on dislocations.Lattice mismatched epitaxial layers that exceed the limits of equilibrium thermodynamics will degrade under sufficient thermal processing by converting the as-grown coherent epitaxy into a network of strain-relieving dislocations. After presenting the effects of strain on band structure, we describe the stability criterion for rapid-thermal processing of strained-layer structures and the effects of exceeding the thermodynamic limits. Finally, device results are reviewed for structures that benefit from high temperature processing of strained-layer superlattices.

Rapid Thermal Processing for Strained-Layer Semiconductor Devices

1993 ◽  
Vol 300 ◽  
Author(s):  
John C. Zolper ◽  
David R. Myers
Keyword(s):  
Band Structure ◽  
Semiconductor Lasers ◽  
Thermal Processing ◽  
Rapid Thermal Processing ◽  
Strained Layer ◽  
Layer Structures ◽  
Thermodynamic Limits ◽  
The Stability ◽  
Mismatched Heteroepitaxy ◽  
Strained Layer Superlattices

ABSTRACTStrained-layer semiconductors have revolutionized modern heterostructure devices by exploiting the modification of semiconductor band structure associated with the coherent strain of lattice-mismatched heteroepitaxy. The modified band structure improves transport of holes in heterostructures and enhances the operation of semiconductor lasers. Strainedlayer epitaxy also can create materials whose band gaps match wavelengths (e. g. 1.06 μm and 1.32 μm) not attainable in ternary epitaxial systems lattice matched to binary substrates. Other benefits arise from metallurgical effects of modulated strain fields on dislocations.Lattice mismatched epitaxial layers that exceed the limits of equilibrium thermodynamics will degrade under sufficient thermal processing by converting the as-grown coherent epitaxy into a network of strain-relieving dislocations. After presenting the effects of strain on band structure, we describe the stability criterion for rapid-thermal processing of strained-layer structures and the effects of exceeding the thermodynamic limits. Finally, device results are reviewed for structures that benefit from high temperature processing of strained-layer superlattices.

scholarly journals The Nature and Origin of Lateral Composition Modulations in Short-Period Strained-Layer Superlattices

1999 ◽  
Vol 583 ◽  
Author(s):  
A. G. Norman ◽  
S. P. Ahrenkiel ◽  
H. R. Moutinho ◽  
C. Ballif ◽  
M. M. Al-Jassim ◽  
...  
Keyword(s):  
Mole Fraction ◽  
Great Promise ◽  
Strained Layer ◽  
Force Microscopy ◽  
Growth Plane ◽  
Transmission Electron ◽  
Inp Substrate ◽  
Short Period ◽  
The Individual ◽  
Strained Layer Superlattices

AbstractThe nature and origin of lateral composition modulations in (AlAs)m(InAs)n short-period strained-layer superlattices grown by molecular beam epitaxy on InP substrates have been investigated by x-ray diffraction, atomic force microscopy, and transmission electron microscopy. Strong modulations were observed for growth temperatures between ≈ 540 and 560° C. The maximum strength of modulations was found for SPS samples with InAs mole fraction x (= n/(n+m)) close to ≈ 0.50 and when n ≈ m ≈ 2. The modulations were suppressed at both high and low values of x. For x > 0.52 (global compression), the modulations were along the <100> directions in the (001) growth plane. For x < 0.52 (global tension), the modulations were along the two <310> directions rotated ≈ ±27° from [110] in the growth plane. The remarkably constant wavelength of the modulations, between ≈ 20–30 nm, and the different modulation directions observed, suggest that the origin of the modulations is due to surface roughening associated with the high misfit between the individual SPS layers and the InP substrate. Highly uniform unidirectional modulations have been grown by control of the InAs mole fraction and growth on suitably offcut substrates, which show great promise for application in device structures.

Cross-sectional Transmission Electron Microscopy of (AlAs)15(InAs)1 Superlattices

1990 ◽  
Vol 48 (4) ◽  
pp. 678-679
Author(s):  
C. Ballesteros ◽  
J. Piqueras ◽  
M. Vázquez ◽  
J.P. Silveira ◽  
L. González ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Layer ◽  
Growth Conditions ◽  
Layer By Layer ◽  
High Quality ◽  
Cross Sectional ◽  
Strained Layer ◽  
Transmission Electron ◽  
Strained Layer Superlattices

Multibeam and bright field transmission electron microscopy are used to determine the structure of (InAs)1/(AlAs)15 superlattices. The interest of InAs/AlAs system arises from the large gap difference. The main problem in the obtention of strained layer superlattices (SLS), with a large lattice mismach, 7% is that of controlling the growth process to obtain high quality layers with sharp interfaces.A modification of the conventional MBE technique, Atomic Layer Molecular Beam Epitaxy (ALMBE) seems to be very appropiate for the growth of such strained layer structures. In particular, high quality layers of materials that demand different growth conditions by MBE, like InAs and AlAs can be obtained at a common low substrate temperature (350-400°) by ALMBE due to the ability to force 2D or layer by layer nucleation and growth. Present superlattices are part of a series with structure (AlAs)15/(InAs)n (n = 1, 2, 3 and 5 ml) whose study by HREM is under way in order to determine critical thickness limits.

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