scholarly journals The heterogeneous nucleation of threading dislocations on partial dislocations in III-nitride epilayers

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
J. Smalc-Koziorοwska ◽  
J. Moneta ◽  
P. Chatzopoulou ◽  
I. G. Vasileiadis ◽  
C. Bazioti ◽  
...  
Keyword(s):  
Heterogeneous Nucleation ◽  
Physical Mechanism ◽  
Dislocation Nucleation ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Physical Mechanisms ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Device Applications ◽  
Very High

Abstract III-nitride compound semiconductors are breakthrough materials regarding device applications. However, their heterostructures suffer from very high threading dislocation (TD) densities that impair several aspects of their performance. The physical mechanisms leading to TD nucleation in these materials are still not fully elucidated. An overlooked but apparently important mechanism is their heterogeneous nucleation on domains of basal stacking faults (BSFs). Based on experimental observations by transmission electron microscopy, we present a concise model of this phenomenon occurring in III-nitride alloy heterostructures. Such domains comprise overlapping intrinsic I1 BSFs with parallel translation vectors. Overlapping of two BSFs annihilates most of the local elastic strain of their delimiting partial dislocations. What remains combines to yield partial dislocations that are always of screw character. As a result, TD nucleation becomes geometrically necessary, as well as energetically favorable, due to the coexistence of crystallographically equivalent prismatic facets surrounding the BSF domain. The presented model explains all observed BSF domain morphologies, and constitutes a physical mechanism that provides insight regarding dislocation nucleation in wurtzite-structured alloy epilayers.

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.

Cantilever Epitaxy of GaN on Sapphire: Further Reductions in Dislocation Density

2002 ◽  
Vol 743 ◽  
Author(s):  
D. M. Follstaedt ◽  
P. P. Provencio ◽  
D. D. Koleske ◽  
C. C. Mitchell ◽  
A. A. Allerman ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Processing Conditions ◽  
Optimum Growth ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Threading Dislocation Density

ABSTRACTThe density of vertical threading dislocations at the surface of GaN grown on sapphire by cantilever epitaxy has been reduced with two new approaches. First, narrow mesas (<1 μm wide) were used and {11–22} facets formed over them early in growth to redirect dislocations from vertical to horizontal. Cross-sectional transmission electron microscopy was used to demonstrate this redirection and to identify optimum growth and processing conditions. Second, a GaN nuc-leation layer with delayed 3D → 2D growth transition and inherently lower threading dislocation density was adapted to cantilever epitaxy. Several techniques show that a dislocation density of only 2–3×107/cm2 was achieved by combining these two approaches. We also suggest other developments of cantilever epitaxy for reducing dislocations in heteroepitaxial systems.

Comparison of Growth and Strain Relaxation of Si/Ge Superlattices Under Compressive and Tensile Strain Field

1991 ◽  
Vol 220 ◽  
Author(s):  
Werner Wegscheider ◽  
Karl Eberl ◽  
Gerhard Abstreiter ◽  
Hans Cerva ◽  
Helmut Oppolzer
Keyword(s):  
Growth Parameters ◽  
Strain Relaxation ◽  
Dislocation Nucleation ◽  
Misfit Dislocations ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Short Period ◽  
Low Energy Electron ◽  
Superlattice Period

ABSTRACTOptimization of growth parameters of short period Si/Ge superlattices (SLs) has been achieved via in situ low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) measurements during homo- and heteroepitaxy on Si (001) and Ge (001) substrates. Transmission electron microscopy (TEM) reveals that pseudomorphic SimGe12-m (m = 9 and 3 for growth on Si and Ge, respectively) SLs with extended planar layering can be prepared almost defect-free by a modified molecular beam epitaxy (MBE) technique. Whereas the SLs on Ge can be deposited at a constant substrate temperature, high-quality growth on Si demands for temperature variations of more than 100°C within one superlattice period. Strain relaxation of these SLs with increasing number of periods has been directly compared by means of TEM. For the compressively strained structures grown on Si we found misfit dislocations of the type 60° (a/2)<110>. Under opposite strain conditions i.e. for growth on Ge, strain relief occurs only by microtwin formation through successive glide of 90° (a/6)<211> Shockley partial dislocations. This is consistent with a calculation of the activation energy for both cases based on a homogeneous dislocation nucleation model.

Threading Dislocations in InxGabxAs/GaAs System

1991 ◽  
Vol 240 ◽  
Author(s):  
M. Tamura ◽  
A. Hashimoto ◽  
Y. Nakatsugawa
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Cross Section ◽  
Molecular Beam ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Edge Type ◽  
Transmission Electron ◽  
Fixed Film

ABSTRACTThreading dislocation morphologies and characters, as well as their generation conditions in InxGa1−xAs films grown by molecular-beam epitaxy on GaAs (001) substrates have been examined, mainly using cross-section al transmission electron microscopy (XTEM) as a function of x and film thickness. The formation of severe threading dislocations is detected in epilayers ofx≧0.2 at a fixed film thickness of 3 μm and with film thicknesses greater than 2μmat x=0.2. Most of the observed threading dislocations are 60°- and pure-edge type dislocations along the <211> and [001] directions, respectively. The former type dislocations are mainly observed in layers of x≧0.2; the latter predominantly exist in layers of X≧O.3.

Optimization of SiGe Graded Buffer Defectivity and Throughput by Means of High Growth Temperature and Pre-Threaded Substrates

2005 ◽  
Vol 891 ◽  
Author(s):  
Matthew Erdtmann ◽  
Matthew T. Currie ◽  
Joseph C. Woicik ◽  
David Black
Keyword(s):  
Growth Temperature ◽  
High Growth ◽  
Dislocation Nucleation ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Trade Off ◽  
Dislocation Glide ◽  
Si Substrates ◽  
High Growth Temperature ◽  
Dislocation Densities

ABSTRACTDislocation glide kinetics dictate in relaxed graded buffers a fundamental opposition between the defectivity and throughput. For state-of-the-art Si-based applications, the trade-off between defect level and wafer cost (inversely related to throughput) has made the insertion of SiGe graded buffers into production difficult. We aim to mitigate the trade-off by reporting two advances that enable simultaneous improvements in both defectivity and throughput. The first is use of a high growth temperature to allow very fast dislocation glide velocities and growth rates as high as 1.0 μm/min. The second is the use of “pre-threaded” Si substrates, substrates with an elevated density of threading dislocations. By having dislocation nucleation controlled by uniformly distributed substrate threading dislocations, instead of unpredictable heterogeneous sources, impediments to dislocation glide, such as dislocation bundles and pile-ups, are reduced. By incorporating both advances into SiGe graded buffer epitaxy, dislocation pile-up densities are reduced by nearly three orders of magnitude, threading dislocation densities are reduced by a factor of 7.4×, and wafer throughput is increased at least 33%.

scholarly journals TEM Observation of the Dislocations Nucleated from Cracks inside Lightly or Heavily Doped Czochralski Silicon Wafers

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Seiji Shiba ◽  
Koji Sueoka
Keyword(s):  
Electron Microscopy ◽  
Crack Propagation ◽  
Room Temperature ◽  
Dopant Concentration ◽  
Dislocation Nucleation ◽  
Czochralski Silicon ◽  
Hardness Tester ◽  
Transmission Electron ◽  
Heavily Doped ◽  
Very High

The crack propagation from the indent introduced with a Vickers hardness tester at room temperature and the dislocation nucleation from the cracks at 900°C inside lightly boron (B), heavily B, or heavily arsenic (As) doped Czochralski (CZ) Si wafers were investigated with transmission electron microscopy (TEM) observations. It was found that the dopant concentration and the dopant type did not significantly affect the crack propagation and the dislocation nucleation. The slip dislocations with a density of about (0.8∼2.8) × 1013/cm3were nucleated from the cracks propagated about 10 μm in depth. Furthermore, small dislocations that nucleated with very high density and without cracks were found around the indent introduced at 1000°C.

Evidence of the De-multiplication Interactions Between Threading Dislocations in GaN Films Grown on (0001) Sapphire Substrates

2007 ◽  
Vol 994 ◽  
Author(s):  
Cheng-Liang Wang ◽  
Jyh-Rong Gong
Keyword(s):  
Type A ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Organometallic Vapor Phase Epitaxy ◽  
Reduced Pressure ◽  
Sapphire Substrates ◽  
Multiplication Process ◽  
Transmission Electron ◽  
Type C

AbstractWe report the observation of threading dislocation de-multiplication process by transmission electron microscopy (TEM). The GaN films used in this study were grown on (0001) sapphire substrates with LT-GaN buffer layers by reduced pressure organometallic vapor phase epitaxy. By using g · Db = 0 invisibility criterion, it was found that some of TDs were de-multiplicated by interactions among themselves. In particular, type a+c TDs were found to nucleate through the interactions between type a and type c TDs in GaN near the GaN/sapphire interface so that the de-multiplication of TDs in GaN films was achieved.

Analysis of buried oxide layer formation and mechanism of threading dislocation generation in the substoichiometric oxygen dose region

1993 ◽  
Vol 8 (3) ◽  
pp. 523-534 ◽  
Author(s):  
Sadao Nakashima ◽  
Katsutoshi Izumi
Keyword(s):  
Oxide Layer ◽  
Chemical Etching ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Layer Formation ◽  
Si Substrate ◽  
Dislocation Generation ◽  
Cross Sectional ◽  
Buried Oxide ◽  
Transmission Electron

The structure of SIMOX wafers implanted at 180 keV with doses of 0.1 × 1018-2.0 × 101816O+ cm−2 at 550 °C, followed by annealing over the temperature range of 1050–1350 °C, has been investigated using cross-sectional transmission electron microscopy and a chemical etching. With doses of 0.35 × 1018-0.4 × 1018 cm−2, a continuous buried oxide layer having no Si island inside is formed by high-temperature annealing at 1350 °C. At a dose of 0.7 × 1018 cm−2, multilayered oxide striations appear in the as-implanted wafer. These striations grow into multiple buried oxide layers after annealing at 1150 °C. The multiple layers lead to a discontinuous buried oxide layer, resulting in the formation of a number of Si micropaths between the top Si layer and the Si substrate when the wafer is annealed at 1350 °C. These Si paths cause the breakdown electric field strength of the buried oxide layer to deteriorate. With doses of 0.2 × 1018-0.3 × 1018 cm−2 and of higher than 1.3 × 1018 cm−2, an extremely high density of threading dislocations is generated in the top Si layer after annealing at 1350 °C. The dislocation density is greatly reduced to less than 103 cm−2 when the oxygen dose falls in the range of 0.35 × 1018-1.2 × 1018 cm−2. Here we propose a mechanism that accounts for the threading dislocation generation at substoichiometric oxygen doses of less than 1.2 × 1018 cm−2.

Dislocations in InAs Epilayers Grown by MBE on GaAs Substrates Under Various Conditions

1998 ◽  
Vol 523 ◽  
Author(s):  
Hongmei Wang ◽  
Yiping Zeng ◽  
Liang Pan ◽  
Hongwei Zhou ◽  
Zhanping Zhu ◽  
...  
Keyword(s):  
Formation Energy ◽  
Molecular Beam ◽  
Transition Process ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Mode Transition ◽  
Gaas Substrates ◽  
Transmission Electron ◽  
Threading Dislocation Density

AbstractUsing Transmission Electron Microscopy, we studied the misfit and threading dislocations in InAs epilayers. All the samples, with thickness around 0.5μm, were grown on GaAs(001) substrates by molecular beam epitaxy under As-rich or In-rich conditions. The As-rich growth undergoes 2D-3D mode transition process, which was inhibited under In-rich surface. High step formation energy under As-deficient reconstruction inhibits the formation of 3D islands and leads to 2D growth. The mechanism of misfit dislocations formation was different under different growth condition which caused the variation of threading dislocation density in the epilayers.

Low-dislocation-density Nonpolar AlN Grown on 4H-SiC (11-20) Substrates

2006 ◽  
Vol 955 ◽  
Author(s):  
Jun Suda ◽  
Masahiro Horita ◽  
Tsunenobu Kimoto
Keyword(s):  
Molecular Beam ◽  
Threading Dislocations ◽  
High Quality ◽  
Fault Density ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Rich Condition ◽  
Very High ◽  
High Phase Purity ◽  
High Phase

ABSTRACTGrowth of AlN on 4H-SiC (11-20) substrates by plasma-assisted molecular-beam epitaxy is presented. Very high-quality AlN can be grown under a slightly Al-rich condition. Transmission electron microscopy revealed that the AlN layer has 4H crystalline structure with high-phase purity (stacking-fault density is 5×106cm−1) and the density of threading dislocations is as small as 8×107cm−2.

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