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.

Low Defect Density Bulk AlN Substrates for High Performance Electronics and Optoelectronics

2012 ◽  
Vol 717-720 ◽  
pp. 1287-1290 ◽  
Author(s):  
Balaji Raghothamachar ◽  
Rafael Dalmau ◽  
Baxter Moody ◽  
H. Spalding Craft ◽  
Raoul Schlesser ◽  
...  
Keyword(s):  
Single Crystal ◽  
Basal Plane ◽  
High Performance ◽  
Defect Density ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Threading Dislocations ◽  
Crystalline Perfection ◽  
X Ray

Using the physical vapor transport (PVT) method, single crystal boules of AlN have been grown and wafers sliced from them have been characterized by synchrotron white beam X-ray topography (SWBXT) in conjunction with optical microscopy. X-ray topographs reveal that the wafers contain dislocations that are inhomogeneously distributed with densities varying from as low as 0 cm-2 to as high as 104 cm-2. Two types of dislocations have been identified: basal plane dislocations and threading dislocations, both having Burgers vectors of type 1/3<112-0> indicating that their origin is likely due to post-growth deformation. In some cases, the dislocations are arranged in low angle grain boundaries. However, large areas of the wafers are nearly dislocation-free and section X-ray topographs of these regions reveal the high crystalline perfection.

Analysis of Dislocation Behavior in Low Dislocation Density, PVT-Grown, Four-Inch Silicon Carbide Single Crystals

2010 ◽  
Vol 1246 ◽  
Author(s):  
Michael Dudley ◽  
Shayan Byrappa ◽  
Huanhuan Wang ◽  
Fangzhen Wu ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Basal Plane ◽  
Growth Conditions ◽  
Formation Mechanisms ◽  
Stress Growth ◽  
Low Dislocation Density ◽  
Basal Plane Dislocation ◽  
Dislocation Behavior ◽  
New Generation ◽  
Insight Into

AbstractSynchrotron White Beam X-ray Topography studies are presented of dislocation behavior and interactions in a new generation of one hundred millimeter diameter, 4H-SiC wafers grown using Physical Vapor Transport (PVT) under specially designed low stress conditions. Such low stress growth conditions have, for example enabled reductions of basal plane dislocation (BPD) densities by two or three orders of magnitude compared to previous levels down to just a few hundred per square centimeter. This provides a unique opportunity to discern details of dislocation behavior which were previously precluded due to complications of image overlap at higher densities. Among the phenomena observed in these studies is the deflection of threading dislocations onto the basal plane producing various stacking fault configurations. Analysis of the contrast from these faults enables determination of their fault vectors which, in turn, provides insight into their possible formation mechanisms.

scholarly journals X-ray characterization of physical-vapor-transport-grown bulk AlN single crystals

2020 ◽  
Vol 53 (4) ◽  
pp. 1080-1086
Author(s):  
Thomas Wicht ◽  
Stephan Müller ◽  
Roland Weingärtner ◽  
Boris Epelbaum ◽  
Sven Besendörfer ◽  
...  
Keyword(s):  
Growth Conditions ◽  
Vapor Transport ◽  
Crystal Quality ◽  
Growth Mode ◽  
Physical Vapor Transport ◽  
Lateral Growth ◽  
Thermomechanical Stress ◽  
X Ray ◽  
Outer Periphery ◽  
Homogeneous Crystal

AlN slices from bulk crystals grown under low thermomechanical stress conditions via the physical vapor transport (PVT) method were analyzed by X-ray methods to study the influence of the growth mode on the crystal quality. Defect types and densities were analyzed along axial [0001] as well as lateral growth directions. X-ray diffraction (0110) rocking-curve mappings of representative wafer cuts reveal a low mean FWHM of 13.4 arcsec, indicating the generally high crystal quality. The total dislocation density of 2 × 103 cm−2 as determined by X-ray topography is low and dislocations are largely threading edge dislocations of b = 1/3〈1120〉 type. The absence of basal plane dislocations in homogeneous crystal regions void of macroscopic defects can be linked to the low-stress growth conditions. Under the investigated growth conditions this high crystal quality can be maintained both along the axial [0001] direction and within lateral growth directions. Exceptions to this are some locally confined, misoriented grains and defect clusters, most of which are directly inherited from the seed or are formed due to the employed seed fixation technique on the outer periphery of the crystals. Seed-shaping experiments indicate no apparent kinetic limitations for an enhanced lateral expansion rate and the resulting crystal quality, specifically with regard to the growth mode on a-face facets.

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.

Synchrotron X-Ray Topography Studies of the Propagation and Post-Growth Mutual Interaction of Threading Growth Dislocations with C-Component of Burgers Vector in PVT-Grown 4H-SiC

2012 ◽  
Vol 717-720 ◽  
pp. 343-346 ◽  
Author(s):  
Fang Zhen Wu ◽  
Huan Huan Wang ◽  
Sha Yan Byrapa ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
...  
Keyword(s):  
Opposite Sign ◽  
Equilibrium Concentration ◽  
Vapor Transport ◽  
Mutual Interaction ◽  
Similar Reaction ◽  
Threading Dislocations ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
Nucleation Sites

Synchrotron White Beam X-ray Topography (SWBXT) imaging of wafers cut parallel to the growth axis from 4H-SiC boules grown using Physical Vapor Transport has enabled visualization of the evolution of the defect microstructure. Here we present observations of the propagation and post-growth mutual interaction of threading growth dislocations with c-component of Burgers vector. Detailed contrast extinction studies reveal the presence of two types of such dislocations: pure c-axis screw dislocations and those with Burgers Vector n1c+n2a, where n1is equal to 1 and n2is equal to 1 or 2. In addition, observations of dislocation propagation show that some of the threading dislocations with c-component of Burgers adopt a curved, slightly helical morphology which can drive the dislocations from adjacent nucleation sites together enabling them to respond to the inter-dislocation forces and react. Since all of the dislocations exhibiting such helical configurations have significant screw component, and in view of the fact that such dislocations are typically not observed to glide, it is believed that such morphologies result in large part from the interaction of a non-equilibrium concentration of vacancies with the originally approximately straight dislocation cores during post-growth cooling. Such interactions can lead to complete or partial Burgers vector annihilation. Among the reactions observed are: (a) the reaction between opposite-sign threading screw dislocations with Burgers vectors c and –c wherein some segments annihilate leaving others in the form of trails of stranded loops comprising closed dislocation dipoles; (b) the reaction between threading dislocations with Burgers vectors of -c+a and c+a wherein the opposite c-components annihilate leaving behind the two a-components; (c) the similar reaction between threading dislocations with Burgers vectors of -c and c+a leaving behind the a-component.

Dislocations in SiC Revealed by NaOH Vapor Etching and a Comparison with X-Ray Topography Taken with Various g-Vectors

2016 ◽  
Vol 858 ◽  
pp. 389-392 ◽  
Author(s):  
Yong Zhao Yao ◽  
Yukari Ishikawa ◽  
Yoshihiro Sugawara ◽  
Koji Sato ◽  
Katsunori Danno ◽  
...  
Keyword(s):  
Threading Dislocations ◽  
Etch Pits ◽  
Burgers Vector ◽  
Monochromatic Beam ◽  
X Ray ◽  
Etch Pit ◽  
Pit Formation ◽  
Dislocation Behavior ◽  
Koh Etching

Threading dislocations (TDs) in 4H-SiC have been studied by comparing etch pits formed by NaOH vapor etching with results of synchrotron monochromatic-beam X-ray topography (XRT) taken under different g-vectors. Burgers vectors determined based on XRT results were utilized to investigate the etch pit characteristics of edge (TED), screw (TSD) and mixed (Burgers vector b=c+a, TMD) threading dislocations. It has been found that pit formation by NaOH vapor etching was very different to that by conventional molten KOH etching. We discuss the possibility of using NaOH vapor etching to distinguish TMDs from TSDs, and report a variety of characteristic etch pits formed by this method and their correlations to dislocation behavior.

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.

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