Basal plane misfit dislocations and stress relaxation in III-nitride semipolar heteroepitaxy

2011 ◽  
Vol 109 (10) ◽  
pp. 103522 ◽  
Author(s):  
Alexey E. Romanov ◽  
Erin C. Young ◽  
Feng Wu ◽  
Anurag Tyagi ◽  
Chad S. Gallinat ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Basal Plane ◽  
Misfit Dislocations

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.

Temperature Dependence of Residual Stresses and Stress Relaxation in Blanket Films of Various Thicknesses

1994 ◽  
Vol 356 ◽  
Author(s):  
A. P. Clarke ◽  
G. Langelaan ◽  
S. Saimoto
Keyword(s):  
Residual Stress ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Back Stress ◽  
Temperature Cycling ◽  
Misfit Dislocations ◽  
X Rays ◽  
Heating Rates ◽  
Residual Strains ◽  
Continuous Temperature

AbstractA rapid method to measure residual strains using x-rays during continuous temperature ramping has been developed whereby resolution of ±5xl0-5 can be attained with 2θ scans of about one minute using low index reflections. The method was used to make residual stress measurements during temperature cycling at heating rates of 2 to 15°C/min with interrupted stress relaxations at 235°C and 130°C on pure Al blanket films of 0.24μm, 0.58μm and 1.01 μm thicknesses. The results are consistent with the notion that surface sources are activated by the back stress of misfit 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.

Trace analysis of non-basal plane misfit stress relaxation in (202¯1) and (303¯1¯) semipolar InGaN/GaN heterostructures

2012 ◽  
Vol 100 (20) ◽  
pp. 202103 ◽  
Author(s):  
Matthew T. Hardy ◽  
Po Shan Hsu ◽  
Feng Wu ◽  
Ingrid L. Koslow ◽  
Erin C. Young ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Trace Analysis ◽  
Basal Plane ◽  
Misfit Stress

Generation of misfit dislocations by basal-plane slip in InGaN∕GaN heterostructures

2006 ◽  
Vol 89 (20) ◽  
pp. 201911 ◽  
Author(s):  
R. Liu ◽  
J. Mei ◽  
S. Srinivasan ◽  
F. A. Ponce ◽  
H. Omiya ◽  
...  
Keyword(s):  
Basal Plane ◽  
Misfit Dislocations

Misfit Dislocations in the Interface between the Metallic and Insulating Phases in Cr Doped V203

1983 ◽  
Vol 31 ◽  
Author(s):  
Nobuo Otsuka ◽  
Hiroshi Sato
Keyword(s):  
Basal Plane ◽  
Room Temperature ◽  
Misfit Dislocations ◽  
Weak Beam ◽  
Principal Axes ◽  
Beam Technique

ABSTRACTThe formation of misfit dislocations in the interface between the metallic and insulating phases which occur in 1.2% Cr doped V203 near room temperature was confirmed by TEM. Orientations of Burgers vectors of misfit dislocations were determined by the weak beam technique. The Burger vectors were parallel to principal axes in the basal plane (<100>) and inclined somewhat to interfaces. The Burgers vectors of misfit dislocations are, however, close enough to the direction of the maximum misfit in the interface. Only one or two misfit dislocations appear in an interface regardless of the thickness of specimens, and these were always located near the surface.

Intersecting basal plane and prismatic stacking fault structures and their formation mechanisms in GaN

2005 ◽  
Vol 892 ◽  
Author(s):  
Jie Bai ◽  
X. Huang ◽  
M. Dudley
Keyword(s):  
Basal Plane ◽  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Formation Mechanisms ◽  
Misfit Dislocations ◽  
Aln Film ◽  
Film Forming ◽  
Fault Structures

AbstractComparative TEM studies have been carried out on GaN/AlN epifilms grown on both on-axis and off-cut 6H-SiC substrates to study the defects formed in the GaN/AlN films and the state of strain relaxation at the interface. Prismatic Stacking Faults (PSFs) are observed to form at I1 type substrate steps in both the on-axis and vicinal samples. In the vicinal samples, the PSFs expand into GaN/AlN film forming intersecting stacking fault configurations comprising faults that fold back and forth from the basal plane (I1 Basal-Plane Stacking Faults; BSFs) to the prismatic plane (PSFs). On the other hand, in the on-axis sample the PSFs are observed to mostly annihilate each other to form enclosed domains confined to the near-interface region. In addition, HRTEM studies suggest the existence of Geometric Partial Misfit Dislocations (GPMDs) at the SiC/AlN interface of the vicinal sample, which form at I2 type substrate steps. These GPMDs simultaneously accommodate the lattice mismatch and stacking sequence mismatch present at the SiC/AlN interface. This provides explanation of the improved strain relaxation observed in the vicinal versus the on-axis sample.

Investigation of Multilayer Systems for Optical Bragg Reflectors by X-ray Double Crystal Topography and - DIF-Fractometry

1991 ◽  
Vol 240 ◽  
Author(s):  
B. Jenichen ◽  
R. Köhler ◽  
R. Hey ◽  
M. Höricke
Keyword(s):  
Stress Relaxation ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Bragg Reflectors ◽  
Double Crystal ◽  
Multilayer Systems ◽  
X Ray ◽  
Different Levels

ABSTRACTOptical Bragg reflectors consisting of the binaries AlAs and GaAs were investigated using double crystal topography and diffractometry. In undoped mirror stacks stress relaxation due to the formation of misfit dislocations was observed, which could be prevented by doping the stacks with 1018cm−3 silicon. In topographs taken in the substrate and different satellite reflections an unusual vanishing of the contrast of different segments of the misfit dislocations takes place, that shows these different segments to be located at different levels of the stack. The contrasts of the threading dislocations are quite similar in the substrate and the satellite reflections whereas the misfit dislocations change their contrast markedly.

Observation of Misfit Dislocations Introduced by Epi-Layer Growth on 4H-SiC

2008 ◽  
Vol 600-603 ◽  
pp. 309-312 ◽  
Author(s):  
Hirofumi Matsuhata ◽  
Hirotaka Yamaguchi ◽  
Ichiro Nagai ◽  
Toshiyuki Ohno ◽  
Ryouji Kosugi ◽  
...  
Keyword(s):  
Basal Plane ◽  
Grazing Incidence ◽  
Lattice Parameter ◽  
Layer Growth ◽  
Misfit Dislocations ◽  
Screw Dislocations ◽  
Incidence Geometries ◽  
The Difference ◽  
Edge Dislocations ◽  
Monochromatic Synchrotron

4H-SiC substrate wafers with epi-layers were observed using monochromatic synchrotron X-ray topography in grazing incidence geometries, to investigate the defects in the epi-layer. Misfit dislocations with b=+1/3[11 2 0] caused by the difference in lattice parameter between the epi-layer and the substrate were observed. The misfit dislocations are located near the interface as edge dislocations, and appear at the top surface as screw dislocations on basal planes. It was observed that more than half of them were introduced from the growing epi-layer surface. The misfit dislocations and some screw dislocations with b=+1/3[11 2 0] are observed to remain as basal plane dislocations at the surface, while other basal plane dislocations were converted to threading edge dislocations in the epi-layer.

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