Strain Relaxation Mechanisms in Lattice Mismatched Epitaxy

1990 ◽  
Vol 198 ◽  
Author(s):  
R. Hull ◽  
J.C. Bean ◽  
J.M. Bonar ◽  
L. Peticolas
Keyword(s):  
Strain Relaxation ◽  
Epitaxial Layers ◽  
Misfit Dislocations ◽  
Strained Layer ◽  
Device Structures ◽  
Lattice Mismatched Epitaxy

ABSTRACTThe relaxation of strained epitaxial layers by the introduction of misfit dislocations is reviewed. Current theoretical and experimental understanding of the nucleation, propagation and interaction of misfit dislocations are summarized. The ramifications for applicability of strained layer epitaxy to practical device structures are discussed.

Stress Relaxation in Uniquely Oriented SiGe/Si Epitaxial Layers

1999 ◽  
Vol 594 ◽  
Author(s):  
M. E. Ware ◽  
R. J. Nemanich
Keyword(s):  
Stress Relaxation ◽  
Surface Morphology ◽  
Strain Relaxation ◽  
Epitaxial Layers ◽  
Misfit Dislocations ◽  
Strained Layers ◽  
Force Microscopy ◽  
Si Substrates ◽  
Atomic Force ◽  
Deposited Films

AbstractThis study explores stress relaxation of epitaxial SiGe layers grown on Si substrates with unique orientations. The crystallographic orientations of the Si substrates used were off-axis from the (001) plane towards the (111) plane by angles, θ = 0, 10, and 22 degrees. We have grown 100nm thick Si(1−x) Ge(x) epitaxial layers with x=0.3 on the Si substrates to examine the relaxation process. The as-deposited films are metastable to the formation of strain relaxing misfit dislocations, and thermal annealing is used to obtain highly relaxed films for comparison. Raman spectroscopy has been used to measure the strain relaxation, and atomic force microscopy has been used to explore the development of surface morphology. The Raman scattering indicated that the strain in the as-deposited films is dependent on the substrate orientation with strained layers grown on Si with 0 and 22 degree orientations while highly relaxed films were grown on the 10 degree substrate. The surface morphology also differed for the substrate orientations. The 10 degree surface is relatively smooth with hut shaped structures oriented at predicted angles relative to the step edges.

Deformation Behavior of Strained Layer Heterostructures

1995 ◽  
Vol 399 ◽  
Author(s):  
A. Fischer ◽  
H. KüHNE
Keyword(s):  
Strain Relaxation ◽  
Equilibrium Theory ◽  
Surface Relaxation ◽  
Image Method ◽  
Surface Boundary ◽  
Misfit Dislocations ◽  
Strained Layer ◽  
Elastic Interactions ◽  
Relaxation Effects ◽  
Surface Boundary Conditions

ABSTRACTWe present a new Volterra dislocation approach in equilibrium theory for strain relaxation in heteroepi-taxial semiconductor structures, one which includes surface relaxation effects and elastic interactions between straight misfit dislocations. The free-surface boundary conditions are satisfied by placing an image dislocation outside the crystal in such a manner that its stress field cancels that of the real interface misfit dislocation at the surface. The effect of the Airy stress function that removes the fictitious shear and normal stresses at the surface are discussed. This image method provides an equilibrium theory which correctly predicts critical strained layer thicknesses and completely describes the elastic and plastic strain relief as well as the phenomenon of work hardening in lattice mismatched epilayers.

Lattice Engineering Using Lateral Oxidation of Alas: an Approach to Generate Substrates With New Lattice Constants

1998 ◽  
Vol 535 ◽  
Author(s):  
P.M. Chavarkar ◽  
L. Zhao ◽  
S. Keller ◽  
K.A. Black ◽  
E. Hu ◽  
...  
Keyword(s):  
Strain Relaxation ◽  
Local Strain ◽  
Epitaxial Layers ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Reactive Material ◽  
New Approach ◽  
Lattice Constants ◽  
Lateral Oxidation ◽  
Threading Dislocation Density

AbstractWe demonstrate a new approach to the growth of dislocation free lattice-mismatched materials on GaAs substrates using Al2O3 interlayers obtained by lateral oxidation of AlAs. This is achieved by generating relaxed low threading dislocation density InGaAs templates which are mechanically supported but epitaxially decoupled from the host GaAs substrate. This process uses the phenomena of relaxation of strained coherent hypercritical thickness (h > hcritical,) layer in direct contact with an oxidizing Al-containing semiconductor (i.e. AlAs or AlGaAs). 5000 Å In0.11Ga0.89As layers were then grown on the In0.2 Ga0.8As/Al2O3/GaAs template which acts as a pseudo-substrate (lattice-engineered substrate). The epitaxial layers are partially relaxed and have extremely smooth surface morphology. Further TEM micrographs of these epitaxial layers show no misfit dislocations or related localized strain fields at the In0.2Ga0.8As/Al2O3 interface. The absence of misfit dislocations or local strain contrast at the In0.2Ga0.8As/Al2O3 interface is attributed to both reactive material removal during the oxidation process and the porous nature of the oxide itself. We propose that the strain relaxation in In0.3Ga0.7As is enhanced due to the absence of misfit dislocations at the In0.2Ga0.8As/A12O3 interface.

“Barrierless” Misfit Dislocation Nucleation in SiGe/Si Strained Layer Epitaxy

1992 ◽  
Vol 263 ◽  
Author(s):  
D.D. Perovic ◽  
D.C. Houghton
Keyword(s):  
Activation Energy ◽  
Misfit Dislocation ◽  
Strain Relaxation ◽  
Dislocation Nucleation ◽  
Theoretical Treatment ◽  
Misfit Dislocations ◽  
Plan View ◽  
Strained Layer ◽  
Wide Range ◽  
Peierls Barrier

ABSTRACTThe study of the critical thickness/strain phenomenon inherent in metastable, layered heterostructures has led to the development of several models which describe elastic strain relaxation. Hitherto, the nucleation of misfit dislocations required for coherency breakdown is the least well understood aspect of strain relaxation, due to the paucity of experimental data. Moreover, existing theoretical calculations predict relatively large activation energy barriers (>10 eV) for misfit dislocation nucleation in relatively low misfit (<2%) systems. In this work it will be shown that the nucleation of misfit dislocations can occur spontaneously demonstrating a vanishingly small activation energy barrier. Specifically, experimental studies of a wide range of GexSi1−x/Si (x< 0.5) hetero-structures, grown by MBE and CVD techniques, have provided quantitative data from bulk specimens on the observed misfit dislocation nucleation rate and activation energy using large-area diagnostic techniques (eg. chemical etching/Nomarski microscopy). In parallel, the strained layer microstructure was studied in detail using crosssectional and plan-view electron microscopy in order to identify a new dislocation nucleation mechanism, the ‘double half-loop’ source. From the combined macroscopic and microscopic analyses, a theoretical treatment has been developed based on nucleation stress and energy criteria which predicts a “barrierless” nucleation process exists even at low misfits (< 1%). Accordingly, the observed misfit dislocation nucleation event has been found both experimentally and theoretically to be rate-controlled solely by Peierls barrier dependent, glide-activated processes with activation energies of ∼2 eV.

scholarly journals Study of Strain Relaxation in InAs/GaAs Strained-layer Superlattices by Raman Spectroscopy and Electron Microscopy

2000 ◽  
Vol 53 (5) ◽  
pp. 697
Author(s):  
A. K. Gutakovsky ◽  
S. M. Pintus ◽  
A. I . Toropov ◽  
N. T. Moshegov ◽  
V. A. Haisler ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Raman Spectroscopy ◽  
Elastic Strain ◽  
Strain Relaxation ◽  
Misfit Dislocations ◽  
Strained Layer ◽  
Transmission Electron ◽  
Dimensional Network ◽  
Order Of Magnitude ◽  
Strained Layer Superlattices

InAs/GaAs strained-layer superlattices (SLS) grown on a GaAs(100) substrate were studied by both Raman spectroscopy (RS) and transmission electron microscopy (TEM). It was shown that the interfaces inside the superlattice are coherent, but the superlattice–substrate interface contain an orthogonal two-dimensional network of 60° misfit dislocations. Using these experimental data values of elastic strain in individual layers and the average values of the residual elastic strain in SLS were determined. The latter are approximately one order of magnitude higher than theoretically predicted data, which suggests that the relaxation of elastic strains was not fully complete. Subsequent annealing of these structures led to the generation of more misfit dislocations, consistent with further relaxation of elastic strain.

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.

Very Thick Coherently Strained GexSi1−x Layers Grown in a Narrow Temperature Window

1991 ◽  
Vol 220 ◽  
Author(s):  
C. H. Chern ◽  
K. L. Wang ◽  
G. Bai ◽  
M. -A. Nicolet
Keyword(s):  
Growth Temperature ◽  
Strain Relaxation ◽  
Gas Pressure ◽  
High Density ◽  
Misfit Dislocations ◽  
High Quality ◽  
Strained Layers ◽  
Temperature Window ◽  
Residual Gas

ABSTRACTStrain relaxation of GexSi1−x layers is studied as a function of growth temperature. Extremely thick coherently strained layers whose thicknesses exceed more than fifty times of the critical thicknesses predicted by Matthews and Blakeslee's model were successfully grown by MBE. There exits a narrow temperature window from 310 °C to 350 °C for growing this kind of high quality thick strained layers. Below this temperature window, the layers are poor in quality as indicated from RHEED patterns. Above this window, the strain of the layers relaxes very fast accompanied with a high density of misfit dislocations as the growth temperature increases. Moreover, for samples grown in this temperature window, the strain relaxation shows a dependence of the residual gas pressure, which has never been reported before.

Low Temperature Device Processing Technology for II-VI Semiconductors

1989 ◽  
Vol 161 ◽  
Author(s):  
D.L. Dreifus ◽  
R.M. Kolbas ◽  
B.P. Sneed ◽  
J.F. Schetzina
Keyword(s):  
Low Temperature ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Epitaxial Layers ◽  
Processing Technologies ◽  
Device Processing ◽  
Device Structures ◽  
Lift Off ◽  
Processing Steps

ABSTRACTLow temperature (<60° C) processing technologies that avoid potentially damaging processing steps have been developed for devices fabricated from II-VI semiconductor epitaxial layers grown by photoassisted molecular beam epitaxy (MBE). These low temperature technologies include: 1) photolithography (1 µm geometries), 2) calibrated etchants (rates as low as 30 Å/s), 3) a metallization lift-off process employing a photoresist profiler, 4) an interlevel metal dielectric, and 5) an insulator technology for metal-insulator-semiconductor (MIS) structures. A number of first demonstration devices including field-effect transistors and p-n junctions have been fabricated from II-VI epitaxial layers grown by photoassisted MBE and processed using the technology described here. In this paper, two advanced device structures, processed at <60° C, will be presented: 1) CdTe:As-CdTe:In p-n junction detectors, grown in situ by photoassisted MBE, and 2) HgCdTe-HgTe-CdZnTe quantum-well modulation-doped field-effect transistors (MODFETs).

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