Direct Observation of Stacking Fault Nucleation from Deflected Threading Dislocations with Burgers Vector c+a in PVT Grown 4H-SiC

2014 ◽  
Vol 1693 ◽  
Author(s):  
Fangzhen Wu ◽  
Huanhuan Wang ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
Stephan G. Mueller ◽  
...  
Keyword(s):  
Direct Observation ◽  
Basal Plane ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Formation Mechanisms ◽  
Threading Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Transmission Geometry ◽  
Made In

ABSTRACTIn our previous studies [1-3], four kinds of stacking faults in 4H-SiC bulk crystal have been distinguished based on their contrast behavior differences in synchrotron white beam x-ray topography images. These faults are Shockley faults, Frank faults, Shockley plus c/2 Frank faults, and Shockley plus c/4 Frank faults. Our proposed formation mechanisms for these stacking faults involve the overgrowth of the surface outcrop associated with threading screw dislocations (TSDs) or threading mixed dislocations (TMDs) with Burgers vector of c+a by macrosteps and the consequent deflection of TSDs or TMDs onto the basal plane. Previous synchrotron x-ray topography observations were made in offcut basal wafers using transmission geometry. In this paper, further evidence is reported to confirm the proposed stacking fault formation mechanism. Observations are made in axially cut slices with surface plane {11-20}. Several kinds of stacking faults are recognized and their contrast behavior agrees with the four kinds previously reported. Direct observation is obtained of a Shockley plus c/4 Frank stacking fault nucleating from a TMD deflected onto the basal plane. The contrast from stacking faults on the basal plane in the axial slices is enhanced by recording images after rotating the crystal about the active -1010 reflection vector enabling a broader projection of the basal plane.

Deflection of Threading Dislocations with Burgers Vector c/c+a Observed in 4H-SiC PVT–Grown Substrates with Associated Stacking Faults

2012 ◽  
Vol 717-720 ◽  
pp. 347-350 ◽  
Author(s):  
Sha Yan Byrapa ◽  
Fang Zhen Wu ◽  
Huan Huan Wang ◽  
Balaji Raghothamachar ◽  
Gloria Choi ◽  
...  
Keyword(s):  
Detailed Analysis ◽  
Basal Plane ◽  
Stacking Faults ◽  
Image Contrast ◽  
Threading Dislocations ◽  
Burgers Vector ◽  
Calculated Phase ◽  
X Ray ◽  
White Beam ◽  
Contrast Studies

A review is presented of Synchrotron White Beam X-ray Topography (SWBXT) studies of stacking faults observed in PVT-Grown 4H-SiC crystals. A detailed analysis of various interesting phenomena were performed and one such observation is the deflection of threading dislocations with Burgers vector c/c+a onto the basal plane and associated stacking faults. Based on the model involving macrostep overgrowth of surface outcrops of threading dislocations, SWBXT image contrast studies of these stacking faults on different reflections and comparison with calculated phase shits for postulated fault vectors, has revealed faults to be of basically four types: (a) Frank faults; (b) Shockley faults; (c) Combined Shockley + Frank faults with fault vector s+c/2; (d) Combined Shockley + Frank faults with fault vector s+c/4.

The Nucleation and Propagation of Threading Dislocations with C-Component of Burgers Vector in PVT-Grown 4H-SiC

2013 ◽  
Vol 740-742 ◽  
pp. 217-220 ◽  
Author(s):  
Fang Zhen Wu ◽  
Michael Dudley ◽  
Huan Huan Wang ◽  
Sha Yan Byrapa ◽  
Shun Sun ◽  
...  
Keyword(s):  
Basal Plane ◽  
Opposite Sign ◽  
Growth Direction ◽  
Threading Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
White Beam

Studies of threading dislocations with Burgers vector of c+a have been carried out using synchrotron white beam X-ray topography. The nucleation and propagation of pairs of opposite sign threading c+a dislocations is observed. Overgrowth of inclusions by growth steps leads to lattice closure failure and the stresses associated with this can be relaxed by the nucleation of opposite sign pairs of dislocations with Burgers vector c+a. Once these dislocations are nucleated they propagate along the c-axis growth direction, or can be deflected onto the basal plane by overgrowth of macrosteps. For the c+a dislocations, partial deflection can occasionally occur, e.g. the a-component deflects onto basal plane while the c-component continuously propagates along the growth direction. One factor controlling the details of these deflection processes is suggested to be related to the ratio between the height of the overgrowing macrostep and that of the surface spiral hillock associated with the threading growth dislocations with c-component of Burgers vector.

X-ray characterisation of the basal stacking fault densities of (11-22) GaN

CrystEngComm ◽  
2021 ◽  
Author(s):  
Markus Pristovsek ◽  
Martin Fentrup ◽  
Tongtong Zhu ◽  
Gunnar Kusch ◽  
Colin Humphreys
Keyword(s):  
Basal Plane ◽  
Stacking Faults ◽  
Stacking Fault ◽  
X Ray Diffraction ◽  
X Ray

Basal plane stacking faults (BSF) in GaN (11-22) layers were observed by a laboratory X-ray diffraction (XRD) system. For this, the (11-22) GaN was oriented in the [-12-10] zone for...

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.

Synchrotron X-ray Topographic Analysis of Dislocation Structures in Bulk SiC Single Crystal

2006 ◽  
Vol 527-529 ◽  
pp. 407-410
Author(s):  
Satoshi Yamaguchi ◽  
Daisuke Nakamura ◽  
Itaru Gunjishima ◽  
Yoshiharu Hirose
Keyword(s):  
Basal Plane ◽  
Mixed Type ◽  
Growth Direction ◽  
Threading Dislocations ◽  
Large Network ◽  
Topographic Analysis ◽  
Edge Type ◽  
Burgers Vector ◽  
X Ray ◽  
Growth Method

The detailed properties of the dislocations of SiC crystals were analyzed using ultrahigh-quality substrates manufactured by RAF (repeated a-face) growth method by means of bulk X-ray topography. From this analysis, we could reveal the detailed features of one type of basal plane dislocations and two types of threading dislocations. The basal plane dislocations were screw type with Burgers vector were parallel to <11-20> direction. One of the threading dislocations was mixed type close to screw dislocation parallel to the growth direction with Burgers vector of 1c+na (n=0, 1, 2, …). Another was the edge type parallel to the c-axis, which was lying between two basal plane dislocations. Moreover, these dislocations were found to be connecting with each other, constituting large network structures.

Study of V and Y Shape Frank-Type Stacking Faults Formation in 4H-SiC Epilayer

2014 ◽  
Vol 778-780 ◽  
pp. 332-337 ◽  
Author(s):  
Huan Huan Wang ◽  
Fang Zhen Wu ◽  
Sha Yan Byrapa ◽  
Yu Yang ◽  
Balaji Raghothamachar ◽  
...  
Keyword(s):  
Basal Plane ◽  
Substrate Surface ◽  
Geometric Analysis ◽  
Stacking Faults ◽  
Grazing Incidence ◽  
Threading Dislocations ◽  
X Ray ◽  
Homoepitaxial Layers ◽  
Surface Intersections ◽  
Koh Etching

Nomarski optical microscopic, KOH etching and synchrotron topographic studies are presented of faint needle-like surface morphological features in 4H-SiC homoepitaxial layers. Grazing incidence synchrotron white beam x-ray topographs show V shaped features which transmission topographs reveal to enclose 1/4[0001] Frank-type stacking faults. Some of these V-shaped features have a tail associated with them and are referred to as Y-shaped defects. Geometric analysis of the size and shape of the V-shaped faults indicates that they are fully contained within the epilayer and appear to be nucleated at the substrate/epilayer interface. Detailed analysis shows that the positions of the V-shaped stacking faults match with the positions of c-axis threading dislocations with Burgers vectors of c or c+a in the substrate and thus appear to result from the deflection of these dislocations onto the basal plane during epilayer growth. Similarly, the Y-shaped defects match well with the substrate surface intersections of c-axis threading dislocations with Burgers vectors of c or c+a in the substrate which were deflected onto the basal plane during substrate growth. Based on the observed morphology of these defect configurations we propose a model for their formation mechanism.

Formation Mechanism of Stacking Faults in PVT 4H-SiC Created by Deflection of Threading Dislocations with Burgers Vector c+a

2011 ◽  
Vol 679-680 ◽  
pp. 269-272 ◽  
Author(s):  
Michael Dudley ◽  
Huan Huan Wang ◽  
Fang Zhen Wu ◽  
Sha Yan Byrapa ◽  
Balaji Raghothamachar ◽  
...  
Keyword(s):  
Stacking Faults ◽  
Growth Conditions ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Threading Dislocations ◽  
Stress Growth ◽  
Burgers Vector ◽  
X Ray ◽  
Dislocation Behavior ◽  
New Generation

Synchrotron White Beam X-ray Topography studies are presented of dislocation behavior and interactions in a new generation of seventy-six millimeter diameter, 4H-SiC wafers grown using Physical Vapor Transport under specially designed low stress conditions. Such low stress growth conditions have enabled reductions of dislocation density by two or three orders of magnitude compared to the lowest previously reported levels [1]. In this paper, detailed topography analysis will be presented of the deflection of threading dislocations with Burgers vectors of c and c+a onto the basal plane leading to reductions of the density of such dislocations down to levels of ~187 cm-2. The deflection of the latter type of dislocations produces complex faulted defect configurations and models for their creation are presented and discussed.

scholarly journals Dislocation Arrangement in a Thick LEO GaN Film on Sapphire

2000 ◽  
Vol 5 (S1) ◽  
pp. 97-103
Author(s):  
Kathleen A. Dunn ◽  
Susan E. Babcock ◽  
Donald S. Stone ◽  
Richard J. Matyi ◽  
Ling Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Burgers Vector ◽  
X Ray ◽  
The Third ◽  
Dislocation Arrangement ◽  
Image Position ◽  
Gan Film

Diffraction-contrast TEM, focused probe electron diffraction, and high-resolution X-ray diffraction were used to characterize the dislocation arrangements in a 16µm thick coalesced GaN film grown by MOVPE LEO. As is commonly observed, the threading dislocations that are duplicated from the template above the window bend toward (0001). At the coalescence plane they bend back to lie along [0001] and thread to the surface. In addition, three other sets of dislocations were observed. The first set consists of a wall of parallel dislocations lying in the coalescence plane and nearly parallel to the substrate, with Burgers vector (b) in the (0001) plane. The second set is comprised of rectangular loops with b = 1/3 [110] (perpendicular to the coalescence boundary) which originate in the coalescence boundary and extend laterally into the film on the (100). The third set of dislocations threads laterally through the film along the [100] bar axis with 1/3<110>-type Burgers vectors These sets result in a dislocation density of ∼109 cm−2. High resolution X-ray reciprocal space maps indicate wing tilt of ∼0.5º.

scholarly journals Dissociation Behavior of Dislocations in Ice

Crystals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 386
Author(s):  
Takeo Hondoh
Keyword(s):  
Basal Plane ◽  
Dislocation Line ◽  
Stacking Faults ◽  
Physical Models ◽  
Time Constants ◽  
Burgers Vector ◽  
Partial Dislocations ◽  
Perfect Dislocation ◽  
Low Energies ◽  
Dissociated State

Dislocations in ice behave very differently from those in other materials due to the very low energies of stacking faults in the ice basal plane. As a result, the dislocations dissociate on the basal plane, from a perfect dislocation into two partial dislocations with equilibrium width we ranging from 20 to 500 nm, but what is the timescale to reach this dissociated state? Using physical models, we estimate this timescale by calculating two time-constants: the dissociation-completing time td and the dissociation-beginning time tb. These time constants are calculated for two Burgers vectors as a function of temperature. For perfect dislocations with Burgers vector <c + a>, td is more than one month even at the melting temperature TM, and it exceeds 103 years below −50 ℃, meaning that the dissociation cannot be completed during deformation over laboratory timescales. However, in this case the beginning time tb is less than one second at TM, and it is within several tens of minutes above −50 ℃. These dislocations can glide on non-basal planes until they turn to the dissociated state during deformation, finally resulting in sessile extended dislocations of various widths approaching to the equilibrium value we. In contrast, for perfect dislocations with Burgers vector <a>, td is less than one second above −50 ℃, resulting in glissile extended dislocations with the equilibrium width we on the basal plane. This width is sensitive to the shear stress τ exerted normal to the dislocation line, leading to extension of the intervening stacking fault across the entire crystal grain under commonly accessible stresses. Also, due to the widely dissociated state, dislocations <a> cannot cross-slip to non-basal planes. Such behavior of extended dislocations in ice are notable when compared to those of other materials.

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